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Exercise

EXERCISE

There has been a gradually growing awareness among policy makers and health care professionals of the great importance of appropriate exercise habits to major public health outcomes. It has been known for decades that physical activity prevents heart disease, but data now suggest that, on average, physically active people outlive those who are inactive and that regular physical activity helps to maintain the functional independence of older adults and to enhance the quality of life for people of all ages. The basic elements of an exercise prescription for older adults are presented in Table 1.

  • Examples of balance enhancing activities include T'ai chi movements, standing yoga or ballet postures, tandem standing and walking, standing on one leg, stepping over objects, climbing up and down steps slowly, turning, and standing on heels and toes.
  • Intensity is increased by decreasing the base of support (e.g., progressing from standing on two feet while holding onto the back of a chair to standing on one foot with no hand support); by decreasing other sensory input (e.g., closing eyes or standing on a foam pillow); or by perturbing the center of mass (e.g., holding a heavy object out to one side while maintaining balance, standing on one leg while lifting the other leg out behind the body, or leaning forward as far as possible without falling or moving the feet).

The rationale for the integration of a physical activity prescription into health care for older adults is based on four essential concepts. First, there is a great similarity between the physiologic changes that are attributable to disuse and those which have been typically observed in aging populations, leading to the speculation that the way in which people age may in fact be greatly affected by activity levels. Second, chronic diseases increase with age, and exercise has now been shown to be an independent risk factor and/or potential treatment for most of the major causes of morbidity and mortality in Western societies, a potential that currently is vastly underutilized. Third, traditional medical interventions do not typically address disuse syndromes accompanying chronic disease, which may be responsible for much of their associated disability. Exercise is particularly good at targeting syndromes of disuse. Finally, many pathophysiological aberrations that are central to a disease or its treatment are specifically addressed only by exercise, which therefore deserves a place in the mainstream of medical care, not as an optional adjunct. Therefore, understanding the effects of aging on exercise capacity and how habitual physical activity can modify this relationship in the older adult, including its specific utility in treating medical diseases, is critical for health care practitioners of all disciplines.

Retarding the aging process

In most physiologic systems, there is considerable evidence that the normal aging processes do not result in significant impairment or dysfunction in the absence of pathology, and under resting conditions. However, in response to a stress, the age-related reduction in physiologic reserves causes a loss of regulatory or homeostatic balance. This process has been termed "homeostenosis" (a lessened capacity for fine-tuning of the system). Thus, subtle changes in physical activity patterns over the adult life span cause most people not engaged in athletic pursuits to lose a very large proportion of their physical work capacity before they notice that something is wrong or find that they have crossed a threshold of disability. The second consequence of age-related changes in physiologic capacity is the increased perception of effort associated with submaximal work. Thus a vicious cycle is set up: "usual" aging leading to decreasing exercise capacity, resulting in an elevated perception of effort, subsequently causing avoidance of activity, and finally feeding back to exacerbation of the age-related declines secondary to disuse.

One of the major goals of gerontological research over the past several decades has been to separate the true physiologic changes of aging from changes due to disease or environmental factors, including disuse or underuse of body systems. Numerous studies point out the superior physical condition of those who exercise regularly compared to their more sedentary peers, even in the tenth decade of life. On the other hand, research indicates that years of physiologic aging of diverse organ systems and metabolic functions can be mimicked by short periods of enforced inactivity, such as bed rest, wearing a cast, denervation, or absence of gravitational forces. These two types of studies have led to a theory of disuse and aging which suggests that aging as it is known in modern society is, in many ways, an exercise deficiency syndrome. This implies that people may have far more control over the rate and extent of the aging process than was previously thought.

Minimizing risk factors for chronic disease

Another way to integrate exercise into health care is to view it in light of its potential to reduce risk factors for chronic diseases. As shown in Table 2, the very large potential for exercise to act as a primary prevention tool is obvious from the kinds of risk factors and diseases listed. The major causes of morbidity and mortality (heart disease, stroke, diabetes, cancer, arthritis, functional dependency, hip fracture, and dementia) in the older population, are all more prevalent in individuals who are sedentary as compared to more active peers.

Adjunctive and primary treatment of chronic disease

There are various diseases in which exercise has a potentially valuable role because of its ability to directly treat the pathophysiology of the disease. Examples of this use of exercise are given in table 2. In some cases exercise may provide benefits similar to those of medication or nutritional intervention; in others it may act through an entirely different pathway. The chronic treatment of hypertension and coronary artery disease is clearly a case for management with both standard medical treatments and exercise. Exercise may prevent secondary cardiovascular events as well as minimize the need and risk of multiple drug use or high drug dosages in these conditions.

The benefits of exercise are often most dramatic in individuals in whom medical treatment is already optimized and cannot be pushed further, or when the pathophysiology of the disease itself is not amenable to change. For example, in chronic obstructive pulmonary disease, once bronchospasm has been relieved and oxygen has been supplemented, exercise tolerance may still be very limited due to peripheral skeletal muscle atrophy and inability to effectively extract oxygen and utilize it for aerobic work as a result of years of disuse, poor nutrition, and other factors. However, such peripheral abnormalities can be directly and effectively targeted and treated with progressive endurance training protocols, which have been shown to significantly improve exercise tolerance, functional status, and quality of life in such patients.

The exercise prescription

This section will outline the elements of a prescription designed to stimulate robust adaptation within the major physiologic domains that can be modified by exercise: strength, cardiovascular endurance, flexibility, and balance, as recommended by the American College of Sports Medicine and endorsed by most major medical consensus groups. These elements are discussed separately, because in most cases exercise training is quite specific in its effects, and little crossover will be seen. For example, balance training will not increase one's aerobic capacity or strength. Resistance training is unique in this regard; it has been shown to benefit all of these domains to some extent, with its most powerful effect in the realms of muscle strength and endurance.

Progressive resistance training. Progressive resistance training (PRT) is the process of challenging the skeletal muscle with an unaccustomed stimulus, or load, such that neural and muscle tissue adaptations take place, leading ultimately to increased strength and muscle mass. In this kind of exercise, the muscle is contracted slowly just a few times in each session against a relatively heavy load. Any muscle may be trained in this way, although usually six to twelve major muscle groups with clinical relevance are trained, for a balanced and functional outcome. The most important element of the PRT prescription is the intensity of the load used. It is evident from many years of research and clinical practice that muscle strength and size are increased significantly only when the muscle is loaded at a moderate or high intensity (60100 percent of maximum).

The benefits of PRT are both metabolic and functional. It improves sensitivity to insulin and may therefore be important in both the prevention and the treatment of diabetes. It also increases bone formation and density, and has a role in the prevention and treatment of osteoporosis. It significantly improves muscle strength and is associated with muscle hypertrophy, and is therefore useful whenever muscle weakness or atrophy contributes to disease or dysfunction. Such disease or dysfunction includes falls, frailty, chronic heart failure, chronic lung disease, Parkinson's disease, neuromuscular disease, chronic renal failure, arthritis, and other chronic conditions associated with decreased activity levels and impaired mobility. In addition, PRT has marked psychological benefits, having been shown to improve major depression as well as insomnia, self-efficacy, and emotional well-being in older adults.

The potential risks of PRT are primarily musculoskeletal injury and rarely cardiovascular events (ischemia, arhythnias, hypertension). Musculoskeletal injury is almost entirely preventable with attention to the following points:

  • Adherence to proper form
  • Isolation of the targeted muscle group
  • Slow velocity of lifting
  • Limitation of range of motion to the pain-free arc of movement
  • Avoidance of use of momentum and ballistic movements to complete a lift
  • Use of machines or chairs with good back support
  • Observation of rest periods between sets and rest days between sessions.

Cardiovascular endurance training. Cardiovascular endurance training refers to exercise in which large muscle groups contract many times (thousands of times at a single session) against little or no resistance other than that imposed by gravity. The purpose of this type of training is to increase the maximal amount of aerobic work that can be carried out, as well as to decrease the physiologic response and perceived difficulty of submaximal aerobic workloads. Extensive adaptations in the cardiopulmonary system, peripheral skeletal muscle, circulation, and metabolism are responsible for these changes in exercise capacity and tolerance. Many different kinds of exercise fall into this category, including walking and its derivatives (hiking, running, dancing, stair climbing), as well as biking, swimming, ball sports, etc. The key distinguishing features between activities that are primarily aerobic versus resistive in nature are listed in Table 3. Obviously, there may be some overlap if aerobic activities are altered to increase the loading to muscle, as in resisted stationary cycling or stair-climbing machines. However, such activities are still primarily aerobic in nature, because they do not cause fatigue within a very few contractions, as PRT does, and therefore do not result in the kinds of adaptations in the nervous system and muscle that lead to marked strength gain and hypertrophy.

Overall, walking and its derivations surface as the most widely studied, feasible, safe, accessible, and economical mode of aerobic training for men and women of most ages and states of health. They do not require special equipment or locations, and do not need to be taught or supervised (except in the cognitively impaired, very frail, or medically unstable individual). Walking bears a natural relationship to ordinary activities of daily living, making it easier to integrate into lifestyle and functional tasks than any other mode of exercise. Therefore, it may be more likely to translate into improved functional independence and mobility than other modes of exercise.

The intensity of aerobic exercise refers to the amount of oxygen consumed (VO 2), or energy expended, per minute while performing the activity, which will vary from about 5 kcal/minute for light activities, to 7.5 kcal/minute for moderate activities, to 1012 kcal/minute for very heavy activities. Energy expenditure increases with increasing body weight for weight-bearing aerobic activities, as well as with inclusion of larger muscle mass, and increased work (force x distance) and power output (work/time) demands of the activity. Therefore, the most intensive activities are those which involve the muscles of the arms, legs, and trunk simultaneously, necessitate moving the full body weight through space, and are done at a rapid pace (e.g.. cross-country skiing). Adding extra loading to the body weight (back-pack, weight belt, wrist weights) increases the force needed to move the body part through space, and therefore increases the aerobic intensity of the work performed. The rise in heart rate is directly proportional, in normal individuals, to the increasing oxygen consumption or aerobic workload. Thus, monitoring heart rate has traditionally been a primary means of both prescribing appropriate intensity levels and following training adaptations when direct measurements of oxygen consumption are not available. The relative heart rate reserve (HRR) is the most useful estimate of intensity based on heart rate. Training intensity is normally recommended at approximately 60 to 70 percent of the HRR. It is calculated as is shown below.

HRR = (Maximal heart rate - resting heart rate) + resting heart rate6070% HRR =.6.7(Max HR -resting HR) + resting HR

Therefore, a more easily obtainable and reliable estimate of aerobic intensity is to prescribe a level of "somewhat hard," or 12 to 14 on the Borg scale, which runs from 6 to 20. At this level, the exerciser should note increased pulse and respiratory rate, but still be able to talk. All of the major benefits of aerobic exercise (increased cardiovascular fitness, decreased mortality, decreased incidence of chronic diseases, improved insulin sensitivity, blood pressure, and cholesterol, for example) are attainable with this moderately intense level of aerobic training. As is the case with all other forms of exercise, in order to maintain the same relative training intensity over time, the absolute training load must be increased as fitness improves. The workloads should progress on the basis of ratings of effort at each training session. Once the perceived exertion slips below 12, the intensity of the regimen should be increased to maintain the physiologic stimulus for optimal rates of adaptation. As with PRT, the most common error in aerobic training is failure to progress, which results in an early plateau in cardiovascular and metabolic improvement.

Cardiovascular protection and risk factor reduction appear to require twenty to thirty minutes three days per week, as does improvement in aerobic capacity. Epidemiological studies of mortality, cardiovascular disease, diabetes and functional independence suggest that walking about one mile per day (presumably about twenty minutes at average pace) or expending about 2000 kcal/week in physical activities is protective, again pointing to the moderate levels that are needed for major health outcomes. It has been shown that exercise does not need to be carried out in a single session to provide training effects, and may be broken up into periods of ten minutes at a time.

The risks of exercise are summarized in Table 4. The risk of sudden death during physical activity appears to be limited primarily to those who do not exercise on a regular basis (at least one hour per week), which is another reason for advocating regular, moderate periods of exercise rather than periodic high-volume training.

The benefits of aerobic exercise have been extensively studied since the 1960s (the most important of these for older adults are listed in Table 2). They include a broad range of physiological adaptations that are in general opposite to the effects of aging on most body systems, as well as major health-related clinical outcomes. The health conditions that are responsive to aerobic exercise include most of those of concern to older adults: osteoporosis, heart disease, stroke, breast cancer, diabetes, obesity, hypertension, arthritis, chronic lung disease, depression, and insomnia. These physiological and clinical benefits form the basis for the inclusion of aerobic exercise as an essential component of the overall physical activity prescription for healthy aging.

Flexibility training. Flexibility training includes movements or positions designed to increase range of motion across joints. Such range of motion is determined by both soft tissue factors (muscle strength, muscle and ligament length, scarring from surgery or trauma, joint and bursa fluid, synovial tissue thickness and inflammation, ligament laxity, tissue elasticity, degenerative changes of cartilage, temperature of tissues) and bony structure (deformities, arthritic and degenerative changes in bone, surgical devices). Obviously, only some of these abnormalities are amenable to exercise intervention, and these will be discussed below. In general, the effect of stretching the soft tissues around a joint slowly and consistently over time is to increase the pain-free range of motion for that joint.

Flexibility may be enhanced without the use of any specialized equipment. It is often helpful, however, to have a thin mat available for postures that are best done while stretched out on the floor.

The most effective technique for increasing flexibility is to extend a body part as fully as possible without pain, then hold this fully extended position for twenty to thirty seconds. The key requirement is to complete the movement slowly (without any bouncing or ballistic movements). Such bouncing does not increase efficacy and range of motion, but instead may cause muscle contraction that limits the range achievable. A technique known as proprioceptive neural facilitation (PNF) will maximize the stretching effectiveness. The technique is as follows. Once the body part has been stretched as far as possible, the muscle groups around the joint should then be completely relaxed, while maintaining the stretch. Next, an attempt is made to stretch a little further, which is usually possible. This final position is then held for about twenty to thirty seconds before returning to the initial position. PNF serves to counteract the involuntary resistance to overextension of a joint caused by a feedback loop of receptors within the muscle tissue that are activated by mechanical stretch.

Flexibility exercise is part of many other forms of exercise, such as ballet and modern dance, yoga, t'ai chi, and resistance training, because in all of these pursuits the muscle groups are slowly extended to their full range and held before relaxing, just as in PNF. It is not recommended to force a stretch beyond the point of pain, as this may result in injury to soft tissue structures and ultimately worsen function. As with all forms of exercise, as the range of motion increases over time, it is appropriate and necessary to extend the distance the joint is moved so that progress is maintained.

The physiologic benefit of flexibility exercise is increased range of motion across joints. There is some evidence that range of motion is related to functional independence in activities of daily living, posture, balance, and gait characteristics in older adults, as well as to pain and disability and quality of life in arthritis. Flexibility training itself does not result in improved strength or endurance, or marked improvements in balance. Therefore, it is best conceived of as an accessory to other forms of exercise that contributes to overall exercise and functional capacity. To the extent that pain, fear of falling, mobility, and function are improved, quality of life may improve as well. There is a need for much better quantitative research on effective doses and long-term benefits of this mode of exercise in the elderly.

Balance training. Any activity that increases one's ability to maintain balance in the face of stressors may be considered a balance-enhancing activity. Stressors include decreased base of support; perturbation of the ground support; decrease in proprioception, vision, or vestibular system input; increased compliance of the support surface; or movement of the center of mass of the body. Balance-enhancing activities impact on the central nervous system control of balance and coordination of movement, and/or augment the peripheral neuromuscular system response to signals that balance is threatened.

Intensity in balance training refers to the degree of difficulty of the postures, movements, or routines practiced. The appropriate level of difficulty or "intensity" for any balance-enhancing exercise is the highest level that can be tolerated without inducing a fall or near-fall. Progression in intensity is the key to improvement, as in other exercise domains, but mastery of the previous level before progression must be adhered to for safety.

Balance training has been shown to result in improved balance performance, decreased fear of falling, decreased incidence of falls, and increased ability to participate in activities of daily living that may have been limited by gait and balance difficulties. It is expected, although not proven, that such changes ultimately lead to improvements in functional independence, reduced hip fractures and other serious injuries, and improved overall quality of life.

Summary of benefits

Physiologic aging, retirement, societal expectations, accumulated diseases, and medication and nutritional effects conspire to produce deficits in strength, balance, aerobic capacity, and flexibility in older adults. Fortunately, there is increasing evidence for the reversibility of many of these deficits with a targeted exercise prescription. There is still work to be done in refining the prescription, particularly in terms of the amount of flexibility and balance training needed for optimal efficacy. In addition, there is a need for well-controlled, long-term studies on clinically important outcomes, such as treatment of cardiovascular disease and stroke, prevention and treatment of hip fracture, prevention of diabetic complications, reduction in nursing home admission rates, and moderation of disability from arthritis. An "active lifestyle" may be the most desirable public health approach to the maintenance of function and the prevention of disease in healthy persons. However, it is likely that the use of exercise to treat preexisting diseases and geriatric syndromes will always need to incorporate elements of a traditional "exercise prescription," as well as behavioral approaches, to more fully integrate appropriate physical activity into daily life.

Maria Fiatarone Singh

See also Balance and Mobility; Balance, Sense of; Frailty; Heart Disease; Life Expectancy; Periodic Health Examination; Sarcopenia.

BIBLIOGRAPHY

American College of Sports Medicine. "The Recommended Quantity and Quality of Exercise for Developing and Maintaining Cardiopulmonary and Muscular Fitness in Healthy Adults." Medicine and Science in Sports and Exercise 22 (1990): 265274.

American College of Sports Medicine. Guidelines for Exercise Testing and Prescription. Philadelphia: Williams & Wilkins, 1995.

Blair, S. N.; Kohl, H.; Barlow, C.; et al. "Changes in Physical Fitness and All-Cause Mortality: A Prospective Study of Healthy and Unhealthy Men." Journal of the American Medical Association 273 (1995): 10931098.

Bortz, W. M. "Redefining Human Aging." Journal of the American Geriatrics Society 37 (1989): 10921096.

Drinkwater, B.; Grimson, S.; Cullen-Raab, D.; et al. "ACSM Position Stand on Osteoporosis and Exercise." Medicine and Science in Sports and Exercise 27 (1995): ivii.

Fiatarone Singh, M. Exercise, Nutrition and the Older Woman: Wellness for Women over Fifty Boca Raton, Fla.: CRC Press, 2000.

Helmrich, S.; Ragland, D.; and Paffenbarger, R. "Prevention of Non-Insulin-Dependent Diabetes Mellitus with Physical Activity." Medicine and Science in Sports and Exercise 26 (1994): 824830.

Lee, I.-M.; Paffenbarger, R. S.; and Hennekens, C. H. "Physical Activity, Physical Fitness and Longevity." Aging Clinical and Experimental Research 9 (1997): 211.

Mazzeo, R.; Cavanaugh, P.; Evans, W.; et al. "Exercise and Physical Activity for Older Adults." Medicine and Science in Sports and Exercise 30 (1998): 9921008.

Miller, M.; Rejeski, W.; Reboussin, B.; et al. "Physical Activity, Functional Limitations, and Disability in Older Adults." Journal of the American Geriatrics Society 48 (2000): 12641272.

National Institute of Health, Center for Disease Prevention. "Physical Activity and Cardiovascular Health." Journal of the American Medical Association 276 (1996): 241246.

Pate, R. R.; Pratt, M.; Blair, S. N.; et al. "Physical Activity and Public Health: A Recommendation From the Centers for Disease Control and Prevention and the American College of Sports Medicine." Journal of the American Medical Association 273 (1995): 402407.

Province, M.; Hadley, E.; Hornbrook, M.; et al. "The Effects of Exercise on Falls in Elderly Patients." Journal of the American Medical Association 273 (1995): 13411347.

U.S. Department of Health and Human Services. Physical Activity and Health: A Report of the Surgeon General. Atlanta, Ga.: U.S. Dept. of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, 1996.

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exercise

exercise

Muscle activity

Exercise is muscular activity. When the word is used, there is almost always the additional implication of the activity being extended over time, but for how long is up to the user. More commonly explicit are the adjectives of intensity (mild, moderate, strenuous/high) and body region (leg, upper body/arm). An important distinction, from the point of view of physiological response, is between exercise predominantly involving movement (dynamic exercise) and that in which the muscles brace against each other or an unmoving outside load (static exercise). Static exercise is also known as ‘isometric’ because the muscles stay at (approximately) constant length.

All exercise, then, starts with the activation of voluntary muscle. Whether there is significant movement depends on whether the force the muscle is producing exceeds, matches, or falls short of the load against which it is acting. The first situation produces dynamic exercise of the form we usually think of; technically, the muscles, successfully shortening, are said to be contracting ‘concentrically’. However, the last situation is dynamic too; here the muscles, extending under the greater external force, are active ‘eccentrically’ (often pronounced ‘ee-centrically’). Only in the middle case, where muscle force equals that against which it is acting, will the exercise be static. Finally, it must be made clear that the muscles need not be working flat out in any of these situations. That will depend on their degree of activation by the nervous system; full activation is uncommon in daily life.

The chemical demands of the muscles underlie most of the other phenomena of exercise. In particular, ample supplies of oxygenated blood must be supplied to every active muscle. Both the heart and the circulation, and the respiratory system, respond accordingly. Scientific understanding of these responses, however, depends on our ability to measure both muscular performance and the metabolic energy input upon which it is based.

Measuring muscular performance and metabolic input

It is a fairly simple matter to measure isometric force production. All that is required is a spring balance or, better, an electronic strain gauge, against which the body-part of interest exerts force through a virtually inextensible wire or rigid lever system. Grip strength, bite force, elbow flexion, or knee extension are easily measured by ‘dynamometers’ (force measurers) of this broad type.

In dynamic exercise, measuring force as such is not often sufficient for the physiologist, though transducers placed in bicycle cranks, or in ‘force plates’ let into a rigid laboratory floor, are examples of instruments which can provide this information. The overall demand of dynamic exercise is, however, most completely indicated by the power output achieved by the body, for power embodies both the force and the rate of movement. Power output is assessed by ‘ergometers’ (work measurers), and can be most readily measured for rhythmic movements against external load, such as in cycling or rowing.

The input of energy from metabolism can be estimated with reasonable precision when the exercise lasts long enough at a steady rate for breathing to come into balance with the muscles' demands (‘aerobic’ exercise). Then the effort may be considered to be entirely founded upon the ‘burning’ of fuel molecules in oxygen. As all the body's fuels (carbohydrate, fat, and — normally used to a much lesser extent — protein) release rather similar amounts of energy when reacted with the same volume of oxygen, measurements of the volume of oxygen consumed per minute (V̇o2) are the basis of the energy– input calculations. Such measurements are made by collecting the air breathed out by an exercising subject, assaying the percentage of oxygen left in that air, and subtracting that from the percentage of oxygen which would have been in the same volume of air when it was breathed in. The result gives the ‘aerobic power’ of the subject performing that exercise. The maximum aerobic power a subject can achieve (V̇o2max) is a fundamental indicator of exercise potential.

Changes in heart and circulation

Considering the heart first, its rate of beating rises appreciably even as we stand up and walk gently through the house. In the highest intensity exercise, the pulse rises to its maximum. This varies with the age of the individual, but negligibly with gender and, more surprisingly, only a little with fitness. The thumb rule is that maximum heart rate (HR) (in beats per minute) = 220 - (age in years). People who are trained to sustain high intensity dynamic exercise for periods of many minutes at a time (‘aerobic’ athletes) actually have maximum HRs 10–15 beats per minute lower than would be calculated by that formula. This seeming paradox makes more sense when it is considered that the amount of blood pumped by their hearts in every beat (their ‘stroke volume’, SV) is greater in any given state of rest or exercise than that of an untrained person; thus the aerobic athlete's resting pulse will be slower than the average person's by at least as much as the shortfall at maximum HR, and so allows a greater percentage increase from rest to maximum exercise.

During the responses to increasing exercise intensity there is some increase of SV as well as of HR in everybody, so that in an untrained but healthy young adult, of 70 kg body weight (the standard textbook figure), pulse might rise about threefold, from say 70 beats per minute at rest to 200, SV by about 1.7 times, and thus total cardiac output (CO) from 5 to 25 litres/min. Equivalent figures for the internationally elite aerobic athlete might be from 45 to 185 beats per minute (HR) and 5 to 40 litres/min (CO), implying a near doubling of the already large SV. Notice, however, that the resting CO is the same for both, as the metabolic demands of sitting still are much the same for everybody of a given weight.

Nevertheless, even the élite athlete's eight-fold increase in CO is far from sufficient by itself to explain the total blood flow through each of the muscles that is working flat out. Modern indications are that muscle blood flow can increase by the order of 100-fold from the resting level. Great increases of flow through the active muscles are achieved by dilatation of blood vessels running through them, assisted to some extent by constriction of the vessels supplying organs, such as the gut and kidneys, which do jobs that can take second place during the exercise. (How vessels constrict and dilate is discussed under ‘Blood vessels’.) Finally, the active muscles' metabolism is enabled to increase by yet one more factor — enhanced extraction of oxygen and nutrients from each ml of blood flowing through them. In the case of oxygen, this increase is typically about three-fold.

The limit to maximum power output

Pursuing our figures, if muscle blood flow rose 100-fold and oxygen extraction/ml of blood rose threefold, 300 times as much oxygen would have to be extracted from the air each minute for all muscles in the body to be maximally active at once. Actually, this cannot happen: it has been calculated that the heart can only supply 30–40% of the total musculature, fully active, simultaneously. This puts a significant limitation on running and cycling, and an even more substantial one on activities demanding direct propulsive power from all four limbs — such as cross-country skiing and swimming. Tellingly we find that, if any one of the measures of whole-body effort (such as maximum CO, maximum power output, or maximum oxygen consumption — V̇o2max) is considered, its values over all these exercises are within about 10% of each other — strongly indicating that the chief limitation on them all is a central function upon which each depends. One expression of this central limitation is the ceiling, just noted, on cardiac output.

Changes in breathing

The limit shows itself in respiratory function, too. However, it is not in the obvious feature, ventilation (the volume of air breathed in and out each minute); this increases several times more than CO — namely 15–35-fold, according to aerobic fitness. (Typical patterns of the increase of ventilation during the first few minutes of both moderate and strenuous exercise are described under breathing during exercise.) That the maximum ventilatory rate is more than sufficient to meet requirements is indicated by the fact that oxygen extraction from each litre of air goes slightly down, not up, at high exercise intensities. At such intensities the time available for oxygen to diffuse from the air in the lungs into the blood as it races past, begins to become a limiting factor. In normally healthy people near sea level the limitation is barely, if at all, detectable; but in top athletes racing at sea level the arterial blood, fresh from the lungs, falls clearly short of full saturation with oxygen — comparable to its condition in a resting person at the altitude of an Alpine ski resort.

Anaerobic exercise

A distinction which has been avoided until this point must now be confronted. The discussion has focused on exercise continued long enough (say 4 min or more) that it must be performed in balance with oxygen uptake. Any track race longer than 1500 metres is of this kind once the athlete's body has adjusted fully to the pace. Briefer activities (like a 400 metre race) can be more intense, but only on the basis of the extra power, greater than the aerobic maximum, being supplied via anaerobic metabolic pathways. Such very intensive, short-term exercise is termed ‘anaerobic’; but note that, while aerobic exercise, when we have settled into it, is totally aerobic, even the briefest high-intensity exercise is never wholly anaerobic.

Upper body exercise

Before leaving dynamic exercise, we should note that exercise using only the arms provides less power at a given HR than exercise predominantly using the legs. Among the reasons for this is that external (and therefore measurable) work done by the arms usually requires the trunk to be braced by muscular effort which needs energy but does not move the load.

Static versus dynamic

Bracing actions of the trunk muscles are in fact examples of static exercise. Other instances are the guardsman's posture at attention, the weight-lifter's few seconds of triumph with the bar above his head, and the dinghy crew's efforts to hold the body horizontal over the water, balancing the boat. In all these situations HR is raised (in the latter two instances, very considerably), yet compared with dynamic exercise giving the same HR — especially leg exercise — two things are markedly different:(i) oxygen consumption is much lower;(ii) blood pressure is higher, especially during diastole.

The first point is explicable chiefly by the fact that isometrically contracting muscles require substantially less oxygen than the same muscles cyclically shortening and lengthening. The second arises because, in dynamic exercise, blood flows through the active muscles during the periods of relaxation which alternate with their contractions; during the contraction phases it is impeded. There being no relaxation periods during a static exercise, blood pressure must be raised if any flow at all is to be forced through the tensed muscles. This rise is brought about by reflex mechanisms originating in the muscles themselves.

Hormonal adjustments

In addition to the cardiovascular and respiratory adjustments which the body makes in the face of exercise, substantial hormonal adjustments also occur. Adrenaline flow is elevated, especially in anticipation of vigorous exercise; and as exercise proceeds, cortisol and (particularly in really protracted efforts, such as marathon races) growth hormone concentrations are both substantially raised, and may not return to basal levels for some hours afterwards. All these promote mobilization of both carbohydrate and lipid fuels, and growth hormone also promotes tissue adaptation and repair when the activity is over. Insulin flow, however, is reduced during exercise. This at first seems a paradox, for the function of insulin is to promote glucose entry into tissues such as muscle, and exercising muscle surely needs its glucose? It is now clear that increased availability of glucose transporter molecules in the membranes of exercising muscle fibres enables them to take in glucose with less insulin than usual. Suitably controlled exercise therefore has special benefits for diabetics.

Fuel sources

In short bursts of intensive exercise, carbohydrates are the main fuels used. At lower intensities, fats contribute more and, as endurance efforts proceed, they become the major energy source. Four-fifths of carbohydrate storage is as ‘glycogen’ (animal starch) within the muscle fibres themselves. The rest is as glycogen in the liver, from which it can be released as glucose (blood sugar) when circulating levels fall. However, the brain, which uses no other fuel, makes priority demands, so blood-borne glucose does not contribute a major fraction of the energy used by the muscles in a long event unless its concentration is kept topped up by glucose drinks or carbohydrate food.

Fat is stored both within some muscle fibres and in fat cells. The balance, however, is the converse of that for carbohydrate: most activities seem to draw more upon the fat cells than the intramuscular stores.

Health benefits

Clearly, all exercise constitutes a degree of training for the muscles which it uses. All exercise also enhances cardiovascular and respiratory health to some extent, though aerobic exercise benefits these systems most. The hormonal and metabolic consequences of any but the most severe exercise are almost always advantageous too. Of these benefits, the cardiovascular ones are normally emphasized. Sustained aerobic exercise trains the heart, lowers blood pressure, tends to reduce body fat, and promotes a switch from ‘bad’ to ‘good’ lipids — from low to high density serum lipoprotein — thereby reducing the risk of atheromatous plaques.

How much exercise is necessary, and of what form, has naturally been much researched. Recent work indicates that the most marked gains, relative to a sedentary lifestyle, are achieved by a mere 30 min of moderate exercise (such as brisk walking), on each of 3 days a week. The more exercise is taken, within a normal lifestyle, the greater the health benefit; yet a law of diminishing returns applies.

As to the form of exercise, it is clearly undesirable for an unfit person to leap straight into short-term, high-intensity activity. Worse still, isometric exercise will always, in the short term, raise the blood pressure. So exercise for health, in those who have been sedentary, should be dynamic and essentially aerobic. Such exercise will not build up much muscle. Effort against high resistance, in the weights room or equivalent, is the way to achieve that; but such ‘resistance exercises’ are best not embarked upon by people who have not already achieved a fairly good aerobic fitness base.

Exercise in different cultures

Finally, it may be salutary to recall how rare, and for the most part recent, in human societies is the disposition to take exercise when it could have been avoided. Exercise has been toil, for the great majority of mankind, at least until an industrial revolution was well advanced in the society concerned. Wealth and status thus meant indolence and often corpulence, whether in medieval Europe or over a similar period in China. Yet in such civilizations as that of Sparta and Rome, and in sectors of Japanese society over many centuries, exercise was cultivated in the expectation of war. Perhaps it is ancient Athens that, in its attitudes to exercise as in so many other ways, most closely anticipated our own outlook: exercise for sport, for health, and to maintain/improve the body image were all recognized by the contemporaries of Plato, as they are once more by us. It is to be hoped, however, that our physiological understanding is at least a little better.

Neil Spurway

Bibliography

Bursztyn, P. (1990). Physiology for sportspeople: a serious user's guide to the body. Manchester University Press.
Noakes, T. (1991). Lore of running. Human Kinetics, Champaign, Illinois.
Wilmore, J. H. and and Costill, D. L. (2000). Physiology of sport and exercise. 2nd ed. Human Kinetics, Champaign, Illinois.


See also breathing during exercise; fatigue; fitness; sport.

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COLIN BLAKEMORE and SHELIA JENNETT. "exercise." The Oxford Companion to the Body. 2001. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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Exercise

Exercise

Definition

Exercise is any activity requiring physical exertion done for the sake of health. Activities range from walking and yoga to lifting weights and martial arts .

Origins

Regular exercise as a way of promoting health can be traced back at least 5,000 years to India, where yoga originated. In China, exercises involving martial arts, such as t'ai chi, qigong , and kung fu, developed possibly 2,500 years ago. The ancient Greeks also had exercise programs 2,500 years ago, which led to the first Olympic games in 776 b.c. Other exercise routines have been in use throughout Asia for hundreds of years.

Only within the last 100 years have the scientific and medical communities documented the benefits that even light but regular exercise has on physical and mental health.

The earliest forms of exercise stressed activities that involved stretching and light muscle resistance. Next came martial arts that promoted self-defense. In nearly all forms of Asian exercise routines, some type of meditation was a major component because the ancients believed physical and mental health went together. The ancient Greek and Roman civilizations advocated vigorous physical activity since exercise was associated with military training. The Greeks also believed that a healthy body would promote a healthy mind.

"Physical culture" was popular in the nineteenth and early twentieth centuries. Medical journals showed exercise machines in the 1800s in Europe and North America. Although weight training became popular with a small number of people in the 1940s, it was not until the 1960s that regular exercise programs began to flourish throughout the United States. Gymnasiums, once used mainly by male weight lifters and boxers as training facilities, now are common throughout the United States. Today's gyms and health clubs offer a wide range of exercise activities for men and women that can fit every lifestyle, age group, and exertion level.

Benefits

The medical community recognizes that regular exercise, along with a proper diet, is one of the two most important factors in maintaining good physical and mental health, and in preventing and managing many diseases. Most certified physical trainers advocate at least 20 minutes of exercise at least three times a week. But for people who have a sedentary lifestyle, even walking for 10 minutes a day has health benefits. One study of 13,000 people followed for more than eight years showed that people who walk 30 minutes a day have a significantly reduced risk of premature death than people who did not exercise regularly.

Walking and other cardiovascular exercises can reduce the risk of heart disease , some cancers, hypertension (high blood pressure), arthritis, osteoporosis, stroke , and depression . A study by the Centers for Disease Control and Prevention (CDC) reported in 2001 that running just once a month could help keep bones strong. In addition to physical benefits, a 2001 study showed that exercising just 10 minutes a day can improve mental outlook.

A study released in 2003 reported that exercise combined with behavioral therapy may even help manage the symptoms experienced by Gulf War veterans. Specifically, exercise helped improve symptoms related to fatigue , distress, cognitive problems, and mental health functioning. In the same year, the American Heart Association released a statement saying that exercise was beneficial even for patients awaiting heart transplants. Another study showed that women who participated in strenuous physical activity over a number of years could reduce their risk of breast cancer . Finally, research showed that men and women age 40 to 50 who exercised moderately for 60 to 90 minutes a day were less likely to catch a cold than those who sat around.

Description

Exercise comes in many forms, but there are three basic types: resistance, aerobics, and stretching. Yoga and martial arts are basically muscle stretching routines, walking and running are primarily aerobic, and weight lifting is mainly resistance. However, exercises such as swimming are considered crossover activities since they build muscle and provide a good aerobic, or cardiovascular, workout. Certified physical trainers usually advocate a combination program that involves stretching, aerobics, and at least some resistance activity for 30-60 minutes a day three times a week.

Stretching and meditative exercises

The most common types of alternative health exercises are the ancient disciplines of yoga and the martial arts (such as t'ai chi and qigong).

YOGA. The ancient East Indian discipline of yoga is probably the most widely practiced exercise advocated by alternative health practitioners. This may be because there is a heavy emphasis on mental conditioning as well as physical exertion. Yoga is the practice of incorporating mind, body, and spirit through a series of physical postures, breathing exercises, and meditation. It improves muscle flexibility, strength, and tone while calming the mind and spirit. Most contemporary stress reduction techniques are based on yoga principles.

There are a variety of yoga styles, each with its own unique focus. In the United States, hatha yoga is the most practiced. The pace is slow and involves a lot of stretching and breathing exercises. Much like the Chinese philosophy of yin and yang, hatha yoga strives to balance the opposite forces of ha (sun) and tha (moon). Astanga, or power yoga, involves more intense yoga postures done in rapid succession. Its vigorous workout is especially good in developing muscle strength. Iyengar yoga promotes body alignment while kripalu yoga develops mind, body, and spirit awareness. Pranayama yoga is a series of breathing exercises designed to increase vitality and energy.

Yoga helps strengthen the heart and slow respiration. Studies have shown it is beneficial in treating a variety of conditions, including heart disease, hypertension, arthritis, depression, fatigue, chronic pain , and carpal-tunnel syndrome. A 2001 study at the Cleveland Clinic Foundation in Ohio looked at yoga's effect on people suffering from lower back pain and pain due to conditions like carpal tunnel syndrome and arthritis. After a four-week period, investigators noted that yoga helped lessen pain, improve participants' moods and decreased pain medication requirements.

There are four main groups of yoga postures, also called asanas: standing, seated, reclining prone, and reclining supine. Other groups include forward bends, back bends, side bends, twists, inverted, and balancing. Within each group there are dozens of different yoga poses at beginning and advanced levels.

MARTIAL ARTS. While the words "martial arts" may be associated with conflict, they usually are graceful exercise movements that keep the body and mind strong and healthy. They can be performed by young and old. Martial arts range from simple stretching and meditative exercises to complicated and demanding exercises requiring more physical activity and mental concentration.

Probably the most popular among alternative health participants is t'ai chi, derived from the Chinese philosophy of Taoism and based on the concept of yin and yang. T'ai chi has a self-defense aspect based on counteracting an opponent's attack and then counterattacking, all in the same movement. As an exercise to maintain health, t'ai chi strengthens muscles and joints. It requires deep breathing techniques that increase blood circulation, benefiting the heart, lungs, and other organs. New research states that t'ai chi may improve physical functioning, like bending and lifting, in older age.

Another martial art growing in popularity in the United States is qigong (pronounced chee kung), although it has several forms that are more Taoist and Buddhist than martial. Qigong is a gentle exercise program that can increase vitality, enhance the immune system, and relieve stress when performed regularly. In China, there are hospitals that use qigong to treat terminal illnesses, particularly cancer .

Cardiovascular and aerobic

Aerobic, also called cardiovascular, exercises use a variety of muscle groups continuously and rhythmically, increasing heart rate and breathing. Specific aerobic activities include walking, jogging, running, bicycling, swimming, tennis, and cross-country skiing. Another popular form is aerobic dance exercise. Routines should last 10-60 minutes and be performed at least three times a week. Aerobic exercise is especially beneficial for losing weight and building endurance.

Aerobic exercises can be done outside a formal setting, with little or no equipment. However, since boredom is a frequent cause for stopping exercise, it often is beneficial to participate in exercise classes or join a gym or health club. Exercising with a group often helps with motivation. Also, health clubs usually offer a variety of stationary aerobic equipment, such as bikes, treadmills, stair climbers, and rowing machines.

Resistance

Resistance exercises generally are accomplished by lifting weights such as barbells and dumbbells, or by using a variety of resistance machines. They can also be done using only the body as resistance, such as doing push-ups, pull-ups, and sit-ups. Resistance exercise is particularly good for building muscles. For patients with kidney disease, weight lifting offers added benefit. Chronic kidney disease can lead to muscle wasting, which is compounded by low-protein diets that may be described for these patients. A 2001 study demonstrated that resistance training can improve muscle mass in kidney disease patients.

Unlike aerobics, which can be done daily, weight-lifting exercises require a period for the muscles to rest and rebuild. A total-body workout should be done every other day, or two to three times a week. A more advanced workout would exercise the lower body muscles one day and upper body muscles the next. It is also important to do 5-10 minutes each of warm-up and cool-down exercises, which will help increase flexibility and decrease soreness and fatigue.

Preparations

No advance preparations are required for exercising. However, a trainer can test a person's strength level and outline an appropriate program. Proper shoes are essential, especially for running. Any exercise should start with a warm-up of 5-10 minutes. Anyone considering a regular exercise program should consult first with a doctor, and possibly a sports podiatrist, to avoid strain and injury. Persons with serious health problems, such as heart disease, diabetes, AIDS, asthma , and arthritis should only begin an exercise regimen with their doctor's approval.

Precautions

In most people, the main exercise precaution is to avoid strain and overexertion. Exercise doesn't need to be strenuous to be beneficial. People with certain chronic health problems should take special precautions. Diabetics should closely monitor their blood sugar levels before and after exercising. Heart disease patients should never exercise to the point of chest pain. Exercise can induce asthma. It is essential for people with asthma to get their doctor's permission before starting an exercise program. It also is important for people to be shown the proper form in any activity to avoid strain and possible injury, especially when using exercise equipment. People also should know what parts of the body might be stressed by a particular exercise. They can then use supplemental exercises or stretches to add balance to the exercise program.

Side effects

The primary adverse effects of exercising can be sore muscles and stiff joints a day or two after beginning an exercise routine. These pains may last for several days. Other minor problems can include headaches, dizziness , fatigue, and nausea , usually indicating the exercise routine is too strenuous. A person can agitate old injuries or create new ones by improperly using equipment or wearing inadequately cushioned shoes.

Research & general acceptance

There almost is universal acceptance by allopathic and homeopathic health practitioners that exercise can be beneficial to overall good health. Thousands of studies during the past several decades link regular exercise to reduced risks for heart disease, stroke, diabetes, obesity , depression, hypertension, and osteoporosis. For example, a 1998 study by Harvard University of more than 11,000 people showed that people who exercise for an hour a day cut their risk of stroke in half over people who do not exercise regularly.

Training & certification

No special training or certification is required for exercising. People who want help in developing an exercise program should consult a certified physical trainer.

Resources

BOOKS

Devi, Nischala Joy, and Dean Ornish. The Healing Path of Yoga: Time-Honored Wisdom and Scientifically Proven Methods That Alleviate Stress, Open Your Heart, and Enrich Your Life. New York: Three Rivers Press, 2000.

Feuerstein, Georg, et al. The Yoga Tradition: Its History, Literature, Philosophy and Practice. Prescott, AZ: Hohm Press, 1998.

Goldberg, Linn, and Diane L. Elliot. The Healing Power of Exercise: Your Guide to Preventing and Treating Diabetes, Depression, Heart Disease, High Blood Pressure, Arthritis, and More. New York: John Wiley & Sons, 2000.

McArdle, William D., et al. Essentials of Exercise Physiology. Philadelphia: Lippincott, Williams & Wilkins, 1999.

Norris, Christopher M. The Complete Guide to Stretching. London: A & C Black, 2000.

PERIODICALS

Castaneda, Carmen, et al. "Resistance Training to Counteract the Catabolism of a Low-protein Diet in Patients with Chronic Renal Insufficiency." Annals of Internal Medicine (December 4, 2001): 965912.

"Cognitive Behavioral Therapy Plus Exercise May Alleviate Symptoms." Mental Health Weekly Digest (March 31, 2003): 3.

"Exercise May Help Patients." Heart Disease Weekly (March 30, 2003): 44.

"Fast Facts." Runner's World (November 2001): 24.

Mooney, Linda, and Shelly Reese. "I Fought My Cancer Comeback in the Gym." Prevention (June 1999): 177.

"Stay Active to Stay Cold-Free: A Recent Study Found that You can Ward Off the Sniffle with a Little Exercise." Natural Health (March 2003): 30.

Sternberg, Steve. "Exercise Helps Some Cancer." Science News (May 3, 1997): 269.

"Strenuous Physical Activity Throughout Life can Decrease Risk." Cancer Weekly (March 18, 2003): 32.

"Study is First to Confirm Link Between Exercise and Changes in Brain." Obesity, Fitness and Wellness Week (February 22, 2003): 13.

"Yoga Provides a Fresh Twist on Pain Relief." Tufts University Health and Nutrition Letter (November 2001): 2.

ORGANIZATIONS

Aerobic and Fitness Association of America. 15250 Ventura Blvd., Suite 200, Sherman Oaks, CA 91403. (877) 968-2639. http://www.afaa.com

American Council on Exercise. 5820 Oberlin Dr., Suite 102, San Diego, CA 92121-0378. (858) 535-8227. http://www.acefitness.org

American Society of Exercise Physiologists. Department of Exercise Physiology, The College of St. Scholastica, 1200 Kenwood Ave., Duluth, MN 55811. (218) 723-6297. http://www.css.edu/asep

National Council of Strength & Fitness. P.O. Box 557486, Miami, FL 33255. (800) 772-6273. http://www.ncsf.org

Ken R. Wells

Teresa G. Odle

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Wells, Ken; Odle, Teresa. "Exercise." Gale Encyclopedia of Alternative Medicine. 2005. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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Wells, Ken; Odle, Teresa. "Exercise." Gale Encyclopedia of Alternative Medicine. 2005. Retrieved June 26, 2016 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3435100298.html

Exercise

Exercise

Definition

Exercise is physical activity that is planned, structured, and repetitive for the purpose of conditioning any part of the body. Exercise is utilized to improve health, maintain fitness and is important as a means of physical rehabilitation.

Purpose

Exercise is useful in preventing or treating coronary heart disease, osteoporosis, weakness, diabetes, obesity, and depression. Range of motion is one aspect of exercise important for increasing or maintaining joint function. Strengthening exercises provide appropriate resistance to the muscles to increase endurance and strength. Cardiac rehabilitation exercises are developed and individualized to improve the cardiovascular system for prevention and rehabilitation of cardiac disorders and diseases. A well-balanced exercise program can improve general health, build endurance, and delay many of the effects of aging. The benefits of exercise not only improve physical health, but also enhance emotional well-being.

A study released in 2003 reported that exercise combined with behavioral therapy may even help manage the symptoms experienced by Gulf War veterans. Specifically, exercise helped improve symptoms related to fatigue, distress, cognitive problems and mental health functioning. In the same year, the American Heart Association released a statement saying that exercise was beneficial even for patients awaiting heart transplants. Another study showed that women who participated in strenuous physical activity over a number of years could reduce their risk for breast cancer. Finally, research showed that men and women age 40 to 50 who exercised moderately for 60 to 90 minutes a day were less likely to catch a cold than those who sat around.

Precautions

Before beginning any exercise program, an evaluation by a physician is recommended to rule out any potential health risks. Once health and fitness are determined, and any or all physical restrictions identified, an individual's exercise program should be under the supervision of a health care professional. This is particularly true when exercise is used as a form of rehabilitation. If symptoms of dizziness, nausea, excessive shortness of breath, or chest pain are present during any exercise program, an individual should stop the activity and inform a physician about these symptoms before resuming activity. Exercise equipment must be checked to determine if it can bear the weight of people of all sizes and shapes.

Description

Range of motion exercise

Range of motion exercise refers to activity aimed at improving movement of a specific joint. This motion is influenced by several structures: configuration of bone surfaces within the joint, joint capsule, ligaments, and muscles and tendons acting on the joint. There are three types of range of motion exercises: passive, active, and active assists. Passive range of motion is movement applied to a joint solely by another person or persons or a passive motion machine. When passive range of motion is applied, the joint of an individual receiving exercise is completely relaxed while the outside force moves the body part, such as a leg or arm, throughout the available range. Injury, surgery, or immobilization of a joint may affect the normal joint range of motion. Active range of motion is movement of a joint provided entirely by the individual performing the exercise. In this case, there is no outside force aiding in the movement. Active assist range of motion is described as a joint receiving partial assistance from an outside force. This range of motion may result from the majority of motion applied by an exerciser or by the person or persons assisting the individual. It also may be a half-and-half effort on the joint from each source.

Strengthening exercise

Strengthening exercise increases muscle strength and mass, bone strength, and the body's metabolism. It can help attain and maintain proper weight and improve body image and self-esteem. A certain level of muscle strength is needed to do daily activities, such as walking, running and climbing stairs. Strengthening exercises increase this muscle strength by putting more strain on a muscle than it is normally accustomed to receiving. This increased load stimulates the growth of proteins inside each muscle cell that allow the muscle as a whole to contract. There is evidence indicating that strength training may be better than aerobic exercise alone for improving self-esteem and body image. Weight training allows one immediate feedback, through observation of progress in muscle growth and improved muscle tone. Strengthening exercise can take the form of isometric, isotonic and isokinetic strengthening.

ISOMETRIC EXERCISE. During isometric exercises, muscles contract. However, there is no motion in the affected joints. The muscle fibers maintain a constant length throughout the entire contraction. The exercises are usually performed against an immovable surface or object such as pressing one's hand against a wall. The muscles of the arm are contracting but the wall is not reacting or moving as a result of the physical effort. Isometric training is effective for developing total strength of a particular muscle or group of muscles. It often is used for rehabilitation since the exact area of muscle weakness can be isolated and strengthening can be administered at the proper joint angle. This kind of training can provide a relatively quick and convenient method for overloading and strengthening muscles without any special equipment and with little chance of injury.

ISOTONIC EXERCISE. Isotonic exercise differs from isometric exercise in that there is movement of a joint during the muscle contraction. A classic example of an isotonic exercise is weight training with dumbbells and barbells. As the weight is lifted throughout the range of motion, the muscle shortens and lengthens. Calisthenics are also an example of isotonic exercise. These would include chin-ups, push-ups, and sit-ups, all of which use body weight as the resistance force.

ISOKINETIC EXERCISE. Isokinetic exercise utilizes machines that control the speed of contraction within the range of motion. Isokinetic exercise attempts to combine the best features of both isometrics and weight training. It provides muscular overload at a constant preset speed while a muscle mobilizes its force through the full range of motion. For example, an isokinetic stationary bicycle set at 90 revolutions per minute means that despite how hard and fast the exerciser works, the isokinetic properties of the bicycle will allow the exerciser to pedal only as fast as 90 revolutions per minute. Machines known as Cybex and Biodex provide isokinetic results; they generally are used by physical therapists.

Cardiac rehabilitation

Exercise can be very helpful in prevention and rehabilitation of cardiac disorders and disease. With an individually designed exercise program set at a level considered safe for the individual, people with symptoms of heart failure can substantially improve their fitness levels. The greatest benefit occurs as muscles improve the efficiency of their oxygen use, which reduces the need for the heart to pump as much blood. While such exercise doesn't appear to improve the condition of the heart itself, the increased fitness level reduces the total workload of the heart. The related increase in endurance also should translate into a generally more active lifestyle. Endurance or aerobic routines, such as running, brisk walking, cycling, or swimming, increase the strength and efficiency of the muscles of the heart.

Preparation

A physical examination by a physician is important to determine if strenuous exercise is appropriate or detrimental for an individual. Prior to the exercise program, proper stretching is important to prevent the possibility of soft tissue injury resulting from tight muscles, tendons, ligaments, and other joint-related structures.

Aftercare

Proper cool down after exercise is important in reducing the occurrence of painful muscle spasms. It has been documented that proper cool down also may decrease frequency and intensity of muscle stiffness the day following any exercise program.

Risks

Improper warm up can lead to muscle strains. Overexertion without enough time between exercise sessions to recuperate also can lead to muscle strains, resulting in inactivity due to pain. Stress fractures also are a possibility if activities are strenuous over long periods of time without proper rest. Although exercise is safe for the majority of children and adults, there is still a need for further studies to identify potential risks.

Normal results

Significant health benefits are obtained by including a moderate amount of physical exercise in the form of an exercise prescription. This is much like a drug prescription in that it also helps enhance the health of those who take it in the proper dosage. Physical activity plays a positive role in preventing disease and improving overall health status. People of all ages, both male and female, benefit from regular physical activity. Regular exercise also provides significant psychological benefits and improves quality of life. Studies released in 2003 showed the actual activity in the brain promoted by regular aerobic exercise. It appears that exercise also improves problem solving and other brain-related abilities.

Abnormal results

There is a possibility of exercise burnout if an exercise program is not varied and adequate rest periods are not taken between exercise sessions. Muscle, joint, and cardiac disorders have been noted among people who exercise. However, they often have had preexisting or underlying illnesses.

KEY TERMS

Aerobic Exercise training that is geared to provide a sufficient cardiovascular overload to stimulate increases in cardiac output.

Calisthenics Exercise involving free movement without the aid of equipment.

Endurance The time limit of a person's ability to maintain either a specific force or power involving muscular contractions.

Osteoporosis A disorder characterized by loss of calcium in the bone, leading to thinning of the bones. It occurs frequently in postmenopausal women.

Resources

BOOKS

Bookhout, Mark R., and Grenman, Philip. Principles of Exercise Prescription. Woburn, MA: Butterworth-Heinemann, 2001.

Harr, Eric. The Portable Personal Trainer. New York: Broadway Books, 2001.

McArdle, William D., Frank I. Katch, and Victor L. Katch. Exercise Physiology: Energy, Nutrition, and Human Performance. 5th ed. Philadelphia: Lippincott, 2001.

Redding, Morgan. Physical Fitness : Concepts and Applications. Dubuque, IA: Kendall/Hunt Publishing, 2001.

Roberts, Matt. 90-Day Fitness Plan. Littleton, CO: DK Publishers, 2001.

PERIODICALS

Brun, J. F., M. Dumortier, C. Fedou, and J. Mercier. "Exercise Hypoglycemia in Nondiabetic Subjects." Diabetes and Metabolism 27 (2001): 92-106.

"Cognitive Behavioral Therapy Plus Exercise May Alleviate Symptoms." Mental Health Weekly Digest (March 31, 2003): 3.

Evans, E. M., R. E. Van Pelt, E. F. Binder, D. B. Williams, A. A. Ehsani, and W. M. Kohrt. "Effects of HRT and Exercise Training on Insulin Action, Glucose Tolerance, and Body Composition in Older women." Journal of Applied Physiology 90 (2001): 2033-2040.

"Exercise May Help Patients." Heart Disease Weekly (March 30, 2003): 44.

Killian, K. J. "Is Exercise Tolerance Limited by the Heart or the Lungs?" Clinical Investigations in Medicine 24 (2001): 110-117.

Resnick, B. "Testing a model of exercise behavior in older adults." Research in Nursing and Health 24, no.2 (2001): 83-92.

"Stay Active to Stay Cold-Free: A Recent Study Found that You can Ward Off the Sniffle with a Little Exercise." Natural Health (March 2003): 30.

"Strenuous Physical Activity Throughout Life can Decrease Risk." Cancer Weekly (March 18, 2003): 32.

"Study is First to Confirm Link Between Exercise and Changes in Brain." Obesity, Fitness and Wellness Week (February 22, 2003): 13.

ORGANIZATIONS

American College of Sports Medicine. 401 W. Michigan Street, Indianapolis, IN 46202-3233. (317) 637-9200. Fax: (317) 634-7817. http://www.acsm.org/. mkeckhaver@acsm.org.

American Medical Association. 515 N. State Street, Chicago, IL 60610. (312) 464-5000. http://www.ama-assn.org/.

American Physical Therapy Association. 1111 North Fairfax Street Alexandria, VA 22314. (703) 684-2782. http://www.apta.org.

National Athletic Trainers' Association. 2952 Stemmons Freeway, Dallas, TX 75247-6916. (800) 879-6282 or (214) 637-6282. Fax: (214) 637-2206. http://www.nata.org/.

OTHER

American Diabetes Association. http://www.diabetes.org/exercise.

American Heart Association. http://www.americanheart.org.

American Orthopaedic Society for Sports Medicine. http://www.sportsmed.org.

American Society of Exercise Physiologists. http://www.css.edu/asep.

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Exercise

Exercise

Definition

Exercise is physical activity that is planned, structured, and repetitive for the purpose of conditioning the body. Exercise consists of cardiovascular conditioning, strength and resistance training, and flexibility.

Purpose

Exercise is essential for improving overall health, maintaining fitness, and helping to prevent the development of obesity , hypertension , and cardiovascular disease. Surveys conducted by the Centers for Disease Control and Prevention (CDC) indicate that 61.5 percent of children aged nine to 13 years do not participate in any organized physical activity (for example, sports , dance classes) and 22.6 percent are not physically active during their free time. According to the American Obesity Association, approximately 30 percent of children and adolescents aged six to 19 years are overweight and 15 percent are obese.

A sedentary lifestyle and excess caloric consumption are the primary causes of this increase in overweight and obesity; regular exercise is considered an important factor in controlling weight. Overweight and obese children and adolescents are at higher risk of developing several medical conditions, including the following:

  • asthma
  • diabetes
  • hypertension
  • orthopedic complications, such as hip and knee pain and limited range of motion
  • cardiovascular disease
  • high cholesterol
  • sleep apnea
  • psychosocial disorders, such as depression, negative body image, and eating disorders

Clinical studies have shown that regular exercise has numerous benefits, including the following:

  • preventing weight gain and maintaining healthy weight
  • reducing blood pressure and cholesterol
  • improving coordination
  • improving self-esteem and self-confidence
  • decreasing the risk of developing diabetes, cardiovascular disease, and certain types of cancer
  • increased life expectancy

Description

Exercise consists of cardiovascular conditioning, strength and resistance training, and flexibility to improve and maintain the fitness of the body's heart, lungs, and muscles.

Cardiovascular conditioning

Cardiovascular conditioning involves moderate to vigorous physical activity that results in an elevated heart rate for a sustained period of time. Regular cardiovascular exercise improves the efficiency of the functioning of the heart, lungs, and circulatory system. For adults, aerobic exercise within a target heart rate range calculated based on a maximum heart rate by age is recommended. For healthy children, cardiovascular exercise that elevates the heart rate to no greater than a maximum heart rate of 200 beats per minute is recommended.

In general, the American Heart Association recommends at least 60 minutes of moderate to vigorous physical activity every day for children and adolescents. Cardiovascular conditioning activities should be appropriate for the age, gender, and emotional status of the child. Examples of exercise that elevates the heart rate are bicycle riding, running, swimming, jumping rope, brisk walking, dancing, soccer, and basketball.

Strength and resistance training

Strength and resistance training increases muscle strength and mass, bone strength, and the body's metabolism. Strengthening exercises increase muscle strength by putting more strain on a muscle than it is normally accustomed to receiving. Strength training can be performed with or without special equipment. Strength/resistance training equipment includes handheld dumbbells, resistance machines (Nautilus, Cybex), and elastic bands. Strength training can also be performed without equipment; exercises without equipment include pushups, abdominal crunches, and squats. Children as young as six years can participate in strength training with weights, provided they are supervised by a fitness professional trained in youth strength training. Child-sized resistance machines may be available at some fitness facilities. According to youth strength training guidelines, children and adolescents should perform strength training for approximately 20 minutes two or three times weekly on nonconsecutive days.

Flexibility

Flexibility is important to improve and maintain joint range of motion and reduce the likelihood of muscle strains . Most young children are naturally more flexible than older children and adults and will instinctively perform movements that promote flexibility. As children age, they should be encouraged to continue to stretch. Flexibility is especially important for children and adolescents engaged in vigorous exercise (running, competitive sports). Stretching is best performed following a warm-up and/or at the completion of an exercise session or sport. One activity that promotes flexibility that is increasing in popularity for children is yoga , in the form of children's yoga classes or exercise videos.

Precautions

Before a child begins any exercise program, he or she should be evaluated by a physician in order to rule out any potential health risks. Children and adolescents with physical restrictions or certain medical conditions may require an exercise program supervised by a healthcare professional, such as a physical therapist or exercise physiologist. If dizziness , nausea , excessive shortness of breath, or chest pain occur during any exercise program, the activity should be stopped, and a physician should be consulted before the child resumes the activity. Children and adolescents who use any type of exercise equipment should be supervised by a knowledgeable fitness professional, such as a personal trainer.

Preparation

A physical examination by a physician is important to determine if strenuous exercise is appropriate or detrimental. Prior to beginning exercise, a proper warm-up is necessary to help prevent the possibility of injury resulting from tight muscles, tendons, ligaments, and joints. Appropriate warm-up exercises include walking, light calisthenics, and stretching.

Aftercare

Proper cool-down after exercise is important and should include a gradual decrease in exercise intensity to slowly bring the heart rate back to the normal range, followed by stretches to increase flexibility and reduce the likelihood of muscle soreness. Following vigorous activities that involve sweating, lost fluids should be replaced by drinking water.

Risks

Improper warm-up and inappropriate use of weights can lead to muscle strains. Overexertion without enough time between exercise sessions to recuperate also can lead to muscle strains, resulting in inactivity due to pain. Some children and adolescents may be susceptible to exercise-induced asthma. For children and adolescents who perform high-impact activities, such as running, stress fractures may occur. Dehydration is a risk during longer activities that involve sweating; children and adolescents should be supplied with water during and after activity.

Normal results

Significant health benefits are obtained by including at least a moderate amount of physical exercise for 30 to 60 minutes daily. Regular physical activity plays a positive role in preventing disease and improving overall health status. For children and adolescents just beginning an exercise program, results (including weight loss, increased muscle strength, and aerobic capacity) will be noticeable in four to six weeks.

Parental concerns

Given the increasing prevalence of overweight and obesity in children and adolescents, it is important for parents to encourage regular exercise and also serve as role models by exercising themselves. Television, computers, and video games have replaced physical activity for playtime for the majority of children. Parents should make a commitment to replacing sedentary activities with active indoor and outdoor games. For busy families, exercise can be performed in multiple 10- to 15-minute sessions throughout the day.

For children aged two to five years, physical activities should emphasize basic movement skills, imagination, and play . Examples of appropriate activities for this age group include rolling and bouncing a ball, jumping, hopping, skipping, mimicking animal movements, and pedaling a tricycle.

For children aged five to eight years, physical activities should emphasize basic motor skills and more complex movements (eye-hand coordination). Non-competitive group sports or classes are appropriate for this age, and parents should focus on helping their children find an enjoyable physical activity.

KEY TERMS

Aerobic An organism that grows and thrives only in environments containing oxygen.

Calisthenics Exercise involving free movement without the aid of equipment.

For children aged eight to ten years, physical activities should emphasize the benefits of regular exercise. Team sports and group classes are appropriate for this age. Experts have found that physical activity decreases in this age group, so parents should focus on being supportive and encouraging their children to be physically active.

For children aged 11 to 14 years, physical activities should continue to emphasize the benefits of regular exercise. Participation in team sports, as well as individual activities, such as dance or martial arts, is appropriate for this age. Peer influence and hormonal changes can affect participation in group physical activities, so parents should consider encouraging exercise at home for children reluctant to participate with peers.

Community centers, local YMCAs, health clubs, and other organizations offer age-appropriate exercise programs for children and adolescents led by experienced and knowledgeable instructors. In addition, home exercise videos geared toward children are available in stores and from Web sites.

For children and adolescents with medical conditions that may limit exercise or place them at higher risk for exercise-related complications, supervised exercise programs may be available at hospital-based wellness centers.

Resources

BOOKS

Inspire Kids and Teens to Fitness. San Diego, CA: IDEA Health and Fitness Association, 2003.

LeMay, Michelle. Essential Stretch. New York: Berkeley Publishing Group, 2003.

McArdle, William D., Frank I. Katch, and Victor L. Katch. Exercise Physiology: Energy, Nutrition, and Human Performance, 5th ed. Philadelphia: Lippincott, 2001.

PERIODICALS

Anderson, Ross E., and John M. Jakicic. "Physical Activity and Weight Management: Building the Case of Exercise." The Physician and Sports Medicine 31 (November 2003): 3945.

Centers for Disease Control and Prevention. "Physical Activity >Levels among Children Aged 913 YearsUnited States, 2002." Morbidity and Mortality Weekly Report 52 (2003): 78588.

ORGANIZATIONS

Aerobics and Fitness Association of America. 15250 Ventura Blvd, Suite 200, Sherman Oaks, CA 91403. Web site: <www.afaa.com>.

American College of Sports Medicine. 401 W. Michigan Street, Indianapolis, IN 462023233. Web site: <www.acsm.org/>.

American Council on Exercise. 4851 Paramount Drive San Diego, California 92123. Web site: <www.acefitness.org>.

American Heart Association. National Center. 7272 Greenville Ave., Dallas, TX 75231. Web site: <www.americanheart.org>.

WEB SITES

Ekeland, E., et al. "Exercise to Improve Self-Esteem in Children and Young People." The Cochrane Collaboration, 2004. Available online at <www.medscape.com/viewarticle/486742> (accessed November 29, 2004).

IDEA Health and Fitness Association. Fitness for Your Child. 2004. <www.ideafit.com/articles/fitness_child.asp> (accessed November 29, 2004).

"Physical Education for Preschoolers." KID-FIT, 2004. Available online at <www.kid-fit.com> (accessed November 29, 2004).

Jennifer E. Sisk, MA

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Exercise

Exercise

More than 28 percent of Americans are completely sedentary (they engage in no physical activity), with an additional 60 percent being inadequately active (engaging in less than 30 minutes of activity per day). For those who strive to achieve and maintain a high quality of health, it must be recognized that physical activity is vital to optimal health. This is reaffirmed by numerous studies that have found an association between physical activity, health, longevity, and an improved quality of life. In addition, the number of deaths related to sedentary living or obesity is approximately a half-million per year. Physical activity may impact quality of life in several ways: it can be used to improve self-image and self-esteem, physical wellness , and health.

Participation in physical activity can be beneficial for anyone and can be started during any stage of life. One goal of Healthy People 2010, a set of national health objectives established by the U.S. Department of Health and Human Services, is to increase the number of people who participate in daily physical activity. This activity can take many forms, ranging from a regimented exercise program to daily life activities such as house or yard work, walking a pet, or walking around town to complete errands.

Definition of Terms

Physical activity is a broad term that encompasses all forms of muscle movements. These movements can range from sports to lifestyle activities. Furthermore, exercise can be defined as physical activity that is a planned, structured movement of the body designed to enhance physical fitness. Regimented or purposeful exercise consists of a program that includes twenty to sixty minutes of activity at least three to five days a week. Some examples of this type of activity include walking, running, cycling, or swimming.

Exercise may be classified in one of two categories, anaerobic and aerobic , depending on where energy is derived from. There is a distinct difference between the two, and specific training techniques are used to enhance both. Anaerobic exercise does not require oxygen for energy. This is due to the intensity and duration of anaerobic events, which typically are high intensity and last only a few seconds to a minute or two. These activities range from a tennis serve to an eight-hundred-meter run.

Aerobic exercise does require oxygen for energy. This is observed during exercise that is less intense but of longer duration. This energy system is primarily used during events lasting longer than several minutes, such as a two-mile run or the Tour de France bicycle race. The potential does exist that one can use both systems, as in soccer, where a match requires ninety minutes of continual activity with short intense bursts of effort.

Benefits of Exercise

The American College of Sports Medicine (ACSM), the Centers for Disease Control and Prevention (CDC), and the Surgeon General have all issued statements that recommend placing an emphasis on adopting physical activity into one's lifestyle. Their intention is to make the public more aware of the health benefits associated with increased physical activity, as well as to highlight the amount and intensity of activity necessary to achieve optimal benefits.

There are numerous benefits associated with regular participation in an aerobic exercise program, including improved cardiovascular and respiratory functioning, reduced coronary artery disease (CAD) risk, and increased quality of life. Beneficial improvements in cardiovascular and respiratory function include an increased ability of exercising muscles to consume oxygen, lowered resting and exercise heart rates, increased stamina, resistance to fatigue , more effective management of diabetes , reduced bone-mineral loss, decreased blood pressure , and increased efficiency of the heart. Although it is recognized that specific exercises can be used for the purpose of increasing strength, muscular endurance, and flexibility, it is important to recognize that cardiovascular exercise has the most dramatic effect on the body. This is because cardiovascular exercise engages large muscle groups in an aerobic manner.

Role of Exercise in Disease Prevention

Studies have shown that exercise can have a direct effect on preventing heart disease , cancer , and other causes of premature death. Furthermore, participation in regular physical activity may reduce the rate of occurrence of these maladies. An inverse relationship exists between disease and exercise, meaning that with increased levels of physical activity there is a decreased prevalence for certain diseases. Currently, there is strong evidence that exercise has powerful effects on mortality, CAD (including blood lipid profiles), and colon cancer. Research has also confirmed that aerobic exercise can reduce high blood pressure , obesity, type II diabetes, and osteoporosis . In addition, stroke and several types of cancer (such as breast, prostate , and lung cancer) can also be reduced with regular physical activity.

Even more important, several of these factors are interrelated. For example, when an individual lowers his or her high blood pressure, the risk for heart disease, stroke, and kidney disease is also reduced. Another example is that exercise favorably alters blood lipid profiles. These profiles include measurements of total cholesterol (TC, complete count of all cholesterol in the blood), high-density lipoprotein cholesterol (HDL-C, the "good" cholesterol), low-density lipoprotein cholesterol (LDL-C, the "bad" cholesterol), and triglycerides (TRG, storage form of energy), which reduce the risk of plaque buildup in the coronary arteries, a sign of CAD.

Exercise Prescription

Adequate physical activity is dependent on having a well-rounded program that encompasses all aspects of improving health and preventing disease. A well-rounded program includes cardiovascular fitness, muscular strength and endurance, flexibility, posture, and maintenance of body composition.

Components of Physical Fitness

Cardiovascular Fitness

The ability of the body to perform prolonged, large-muscle, dynamic exercise at moderate to high levels of intensity. This is dependent on the ability of the heart and lungs to deliver oxygen to the working muscles. As fitness levels improve, the body functions more efficiently and the heart can better withstand the strains of everyday stress.

Muscular Strength

The maximal amount of force a muscle can exert with a single maximal effort. Strong muscles are important for carrying out everyday tasks, such as carrying groceries, doing yard work, and climbing stairs. Muscular strength can help to keep the body in proper alignment, prevent back and leg pain, and provide support for good posture.

Muscular Endurance

The ability of a muscle or group of muscles to perform repetitive contractions over a period of time. Endurance is a key for everyday life activities and operates with muscular endurance to help maintain good posture and prevent back and leg pain. In addition, endurance can enhance performance during sporting events, as well as help an individual cope with everyday stress.

Flexibility

This refers to the range of motion in a joint or group of joints, correlated with muscle length. This component becomes more important as people age and their joints stiffen up, preventing them from doing everyday tasks. Additionally, good range of motion will allow the body to assume more nautral positions to help maintain good posture. Stretching is therefore an important habit to start, as well as continue, as one ages.

Body Composition

The relative proportion of fat-free mass to fat mass in the body. Fat-free mass is composed of muscle, bone, organs, and water, whereas fat is the underlying adipose tissue. Excessive fat is a good predictor of health problems because it is associated with cardiovascular disease, high cholesterol, and high blood pressure. Higher proportions of fat-free mass indicate an increase in muscle, and thus an increased ability to adapt to everyday stress.

The most effective way to participate in a well-rounded program is by following a simple mnemonic device called FITT (Frequency, Intensity, Time, Type). The FITT principle includes how many times a week one should exercise (frequency), how intense the workout should be (intensity), how long the workout is (time), and what modality to use (type of exercise). Modality is dependent primarily on what an individual prefers. This exercise prescription in based on an individual's fitness level when entering the exercise program, and ultimately upon the goals of the individual. For example, an untrained individual who wants to lose weight and likes to walk would be placed on a program of treadmill or outdoor walking (type), for thirty minutes a day (time), three to five times per week (frequency), and of light to moderate intensity (intensity).

A good example of an exercise program would include three stages. The first stage is a warm-up, where one should complete light calisthenics to activate and warm the muscles, immediately followed by stretching, which helps to maintain flexibility. The second stage is the conditioning stage, which consists of cardiovascular work to enhance the function of the heart and lungs and a resistance-training regimen to strengthen and tone major muscle groups, such as the quadriceps, hamstrings, chest, biceps, triceps, back, and abdominals. The final stage consists of a cool down, or reduction in heart rate to resting levels, as well as stretching again, since the greatest modification in flexibility comes from post-exercise stretching.

Maintenance of physical activity is important to maintain a healthy lifestyle. In addition, it is important to follow an exercise regime that will start slow and gradually increase as fitness level and exercise tolerance increases. The key is to complete at least thirty minutes of activity most days of the week in the form of activities that one enjoys, such as walking, jogging, swimming, aerobic dance, biking, skateboarding, or participating in a sport. This will enable an individual to reach the goals of Healthy People 2010, which include improving the quality of life through fitness with the adoption and maintenance of regular exercise and physical activity programs.

see also Sports Nutrition.

Robert J. Moffatt Sara A. Chelland

Bibliography

American College of Sports Medicine (2000). ACSM's Guidelines for Exercise Testing and Prescription, 6th edition. Philadelphia: Lippincott, Williams & Wilkins.

Corbin, Charles B.; Lindsey, Ruth; and Welk, Greg (2000). Concepts of Physical Fitness and Wellness: A Comprehensive Lifestyle Approach, 3rd edition. Boston: McGraw-Hill.

McArdle, William D.; Katch, Frank I.; and Katch, Victor L. (2001). Essentials of Exercise Physiology. Philadelphia: Lea & Faber.

Robbins, Gwen; Powers, Debbie; and Burgess, Sharon (2002). A Wellness Way of Life, 5th edition. Boston: McGraw-Hill.

United States Department of Health and Human Services (1996). Physical Activity and Health: A Report of the Surgeon General. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention.

Wallace, Janet P. (2001). "Health Benefits of Exercise and Fitness." In Foundations of Exercise Science, ed. Gary Kamen. Philadelphia: Lippincott, Williams & Wilkins.

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Exercise

Exercise

Definition

The Surgeon General of the United States defines exercise as physical activity that involves planned, structured, and repetitive bodily movements in order to improve or maintain physical fitness. As an element of health, exercise involves both strength training of the muscles and cardiovascular fitness, with stretching activities for flexibility. Most research on physical activity for fitness stresses the intensity and regularity of exercise as key elements. Typical exercise activities include fast walking, running, cycling, swimming, or aerobics classes. The latest Centers for Disease Control and Prevention report, in conjunction with the American Council on Sports Medicine, recommends that all adults perform 30 or more minutes a day of moderate-intensity activity for 57 days per week. The National Institutes of Health Consensus Development Conference Statement on Physical Activity and Cardiovascular Health identifies inactivity as a major public health problem in the United States. They have recommended exercise regimens 57 days a week for people who are already active, and such leisure activities as gardening, walking, using stairs instead of an elevator, cleaning house and recreational pursuits etc., for people who are largely sedentary.


Purpose

One important purpose of exercise is speeding recovery from surgery. Nowhere is being fit as important as when a person is facing surgery or recovering from surgery. Regular exercise leads to important health advantages, including weight loss; greater cardiovascular efficiency; lower cholesterol levels; increased musculoskeletal strength and flexibility; and better functioning of the metabolic, endocrine and immune systems. These effects diminish with lack of exercise within two weeks if physical activity is substantially reduced; the fitness effects disappear altogether within two to eight months if physical activity is not resumed.

With regard to preparing for surgery , the effects of regular exercise on all body systems create optimal responses both to the surgical procedures itself and during the postoperative recovery period.


Demographics

Most adults in North America would benefit from increasing their level of physical activity. The majority of adults in the United States (55%) are overweight, and two-thirds of those with weight problems are likely also to have diabetes, heart disease, high blood pressure, or
other obesity-related conditions. A sedentary lifestyle and unhealthy eating patterns are responsible for at least 300,000 deaths each year from chronic diseases. It is estimated that two-thirds of people over 65 have at least one chronic condition, with 36 million Americans suffering from some form of arthritis. More than 300,000 total joint replacement procedures are performed each year due to osteoarthritis. Lack of physical activity contributes substantially to conditions like osteoarthritis, low back pain, and osteoporosis.

Obesity reached epidemic proportions among adults in the United States in the years between 1987 and 2000. Over 45 million adults are obese; in addition, the percentage of young people who are overweight has more than doubled in the last 20 years. Despite the benefits of physical activity, more than 60% of American adults do not get enough physical activity to provide health benefits. More than 25% are not active in their leisure time. Insufficient activity increases with age; it is also more common in women than men and among those with lower levels of economic stability and educational achievement.

The direct consequences of obesity include:

  • Heart disease and stroke, the leading causes of death and disability in the United States.
  • Type 2 diabetes (also known as NIDDM, or non-insulin-dependent diabetes mellitus).
  • Cancer. Obesity increases the risk of cancer of the uterus, gallbladder, cervix, ovary, breast, and colon in women; it increases the risk of cancer of the colon, rectum, and prostate in men.
  • Osteoarthritis. Obesity adds to daily "wear and tear" on joints, primarily the knees, as well as the hips and lower back.
  • Gallbladder disease. The risk of gallbladder disease and gallstones increases as a person's weight increases.
  • Stress incontinence in women, especially those over 65 years old.
  • Gastroesophageal reflux disease (GERD).

Diagnosis/Preparation

Over 25 million Americans will undergo surgery in 2003. Each patient's surgical risk, complications and outcomes will depend upon how fit they are; how well their cardiovascular and pulmonary systems withstand the stress of anesthesia; how quickly their bones and muscles recover after surgical procedures; and how well their metabolic and immune systems respond to surgery and the risk of infection. The general physical status of the patient is the most important factor in preparing for surgery. This status is determined by the physician, including his or her evaluation of the specific procedures to be performed. On the other hand, however, the patient's lifestyle may affect management of the surgery both before and after the actual procedures. A healthful diet, regular exercise, and quitting smoking are highly recommended before surgery. Each of these factors has an important role to play in optimal functioning of the circulatory and pulmonary systems. Smoking should cease two weeks before surgery to be beneficial.


Aftercare

After surgery, it is important to return to daily activities when the physician gives permission to do so. Most doctors encourage their patients to be as active as possible as soon as possible. While aftercare is individualized, and physicians may place certain limitations on physical activity for specific patients, walking as soon as the patient is able to walk is generally recommended. The patient should be as active as possible within the limits set by the physician for postoperative recovery, with the goal of returning to his or her normal daily activities and exercise routines. The patient should ask the physician for explicit guidelines about returning to an established exercise program or other physical or recreational activities.


Risks

The benefits of exercise before, after surgery and continuing as a daily life activity cannot be overemphasized. There are risks, however, for people who begin an exercise program without having had one in the past. Patients should always have a physical examination before taking up an exercise program for the first time or after a long period of inactivity.

Such high-intensity exercise regimens as high-impact aerobics and jogging are not recommended as often as they once were for helping patients attain a specific fitness level as measured by resting heart rate and muscle mass. Walking, swimming, and gardening can all contribute to aerobic fitness. Strength training with resistance exercises for the arms and legs using weights or bands is now an important aspect of physical fitness. These exercises can be done at a moderate rate, with the number of repetitions increased over time. Stretching is very important to both kinds of exercise activities.


Morbidity and mortality rates

Without exercise and a healthful diet, people burn fewer calories than they take in, resulting in increasing weight gain. While the formula is familiar, the outcomes are surprising. According to studies based on a newer index for obesitythe body mass index or BMIpeople who are overweight or obese have dramatically shorter life spans. In fact, some studies are showing that individuals who are fat in middle age are as likely to lose years of life as those who smoke. Researchers have found obesity and overweight combined are the second leading cause of preventable death in the United States, behind tobacco use. Correlating the BMIcalculated from a person's weight in kilograms divided by height in meters squaredand the mortality of different cohorts of subjects in large longitudinal studies, researchers have found that the lowest mortality rates from all causes were found among those having a BMI between 23.5 and 24.9 for men and 22.023.4 for women. The strongest association between obesity and death from all causes are found among individuals with the highest BMIpeople with a BMI of 40+. Clinical obesity is defined as a BMI of 30 or above. Morbid obesity is defined as a BMI of 40 or above.

With respect to health care, people who are obese have higher rates of complications in the hospital. Researchers in New York studied a group of patients who were in the intensive care unit (ICU) for a variety of causes, and found that those who were morbidly obese were far more likely to die of their illness than those who were closer to their desirable weight (23.3% vs. 6.1%). Patients who were morbidly obese had higher rates of transferrals to nursing homes from the ICU, rather than being discharged to their homesover 16% for the obese patients compared to 3% for patients who were less overweight.


Resources

books

"nutritional disorders: obesity." section 1, chapter 5 in the merck manual of diagnosis and therapy, edited by mark

h. beers, md, and robert berkow, md. whitehouse station, nj: merck research laboratories, 1999.

report of the surgeon general. physical activity and health. centers for disease control and prevention, national center for chronic disease prevention and health promotion, the president's council on physical fitness and sports, 1996. <www.sgreports.nlm.nih.gov >


periodicals

bolliger, c. t. "evaluation of operability before lung resection." current opinion in pulmonary medicine 9 (july 2003): 321-326.

cummings, s., e. s. parham, and g. w. strain. "position of the american dietetic association: weight management." journal of the american dietetic association 102 (august 2002): 1145-1155.

morey, m. c., and c. w. zhu. "improved fitness narrows the symptom-reporting gap between older men and women." journal of women's health (larchmont) 12 (may 2003): 381-390.

pollock, m. l., et al. "resistance exercise in individuals with and without cardiovascular disease: american heart association advisory." circulation 101 (february 22, 2000): 828-833.

wallace, j. "exercise in hypertension: a clinical review." journal of sports medicine 33 (2003): 585-598.

organizations

shape up america! c/o webfront solutions corporation, 15757 crabbs branch way, rockville, md 20855. (301) 258-0540. <www.shapeup.org>.

weight-control information network (win). 1 win way, bethesda, md 20892-3665. (202) 828-1025 or (877) 946-4627.

other

agency for health care practice and research. assessing a patient's willingness to adopt dietary and lifestyle changes is the first step toward sustained weight loss. research archives, no. 237 (may 2000). <www.ahcpr.gov/research/may00/050.>

american association of orthopaedic surgeons. people with chronic conditions benefit from daily exercise. <www.aaos.org/wordhtml/home2.htm,>

national center for chronic disease prevention and health promotion, centers for disease control and prevention. nutrition and physical activity. <www.cdc.gov/nccdphp/dnpa/physical/index.htm.>


Nancy McKenzie, PhD

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McKenzie, Nancy. "Exercise." Gale Encyclopedia of Surgery: A Guide for Patients and Caregivers. 2004. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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Exercise

Exercise

Definition

Exercise is physical activity that is undertaken in order to improve one's health. Physicians, physical therapists, and researchers have found that exercise plays an important role in the maintenance of brain, nerve, and muscle function in the human body. New research suggests that exercise may delay mental deterioration with age and disease, and perhaps even promote neurogenesis (nerve cell growth).

Description

Health care professionals recommend regular exercise because it increases energy, contributes to overall health, improves sleep, increases life expectancy, and enhances lifestyle. In terms of specific medical disorders, exercise has been shown to prevent or delay the onset of coronary artery disease, bone loss and osteoporosis, some types of cancer, and stroke .

Generally, exercise is categorized into the following four types:

  • Aerobic exercise focuses on strengthening the heart, lungs, and circulatory system. Its major goal is to increase the heart rate and breathing rate. Examples of aerobic exercise include jogging, bicycling, swimming, and racket sports.
  • Strength training focuses on strengthening muscles and joints. It also improves balance and increases metabolism. Weightlifting is the most common form of strength training.
  • Balance exercises are used to improve stability. They stimulate the vestibular system, which includes muscles, joints, sensory organs, the inner ear, and the brain.
  • Stretching exercises improve flexibility, which helps prevent injury during other forms of exercises and may decrease chronic pain. Stretching exercises include yoga, tai chi, and basic stretches.

All four types of exercises have been found to be important to maintaining brain, nerve, and muscle health.

Exercise and the brain

Exercise is particularly beneficial to the health of the brain. It has long been known that exercise causes the endocrine system to release serotonin and dopamine, hormones in the brain that produce feelings of euphoria and peacefulness. These hormones often allow people who exercise to think more clearly and perform mental tasks more easily. Exercise has also been successfully used as a treatment for depression , used in lieu of prescription antidepressants.

A 2003 study on mice suggests that new brain cells can grow as a result of exercise. This neurogenesis, previously thought not to occur in adult mammals, is concentrated in the hippocampus, the part of the brain responsible for learning and spatial memory. In addition, the study found that the mice subjected to an exercise regimen had stronger synapses than the mice that were sedentary. Other research shows that nerve growth factors, called neurotropins, are stimulated by exercise. Finally, exercise increases blood flow to the brain, as well as collateral circulation, enhancing mental function and nerve cell stimulation.

Exercise and aging

Aging naturally affects a variety of processes in the human body. Exercise has many positive benefits that prevent or slow the age-related deterioration of brain, nerve, and muscle functions.

In 2001, a study reported by the Mayo Clinic showed that regular exercise in older people slowed rates of mental deterioration, including Alzheimer's disease and dementia . On tests of mental acuity, older people who exercised regularly performed just as well as younger people who did not exercise. Another study found that regular walking greatly slowed rates of mental decline in older women.

Between the ages of 30 and 90, natural aging processes result in the loss of 1525% of the brain tissue. In particular, losses are significant in the parts of the brain consisting of gray matter, which is associated with learning and memory. The February 2003 issue of Journal of Gerontology: Medical Sciences reported that this natural degradation of gray matter in older people was significantly decreased in people who exercised regularly compared to those who did not exercise. In the study, fitness levels were determined by treadmill-walking tests and tissue degradation was measured using magnetic resonance imaging (MRI) .

Balance is often affected as people age. Balance depends on input from the eyes, ears, and other sensory organs, all of which are affected by age. In addition, muscle strength and tone are required for balance. The natural aging process includes contraction of muscle tissue, and sedentary lifestyles only exacerbate the weakening of muscles. Joints supported by strong muscles are more stable than joints that are supported by weak muscles. Strength training, in particular, has the potential to counteract loss of muscle strength.

Physical therapy and the brain, nerves, and muscles

Therapeutic exercises have been designed to enhance a variety of aspects of physical fitness in patients suffering from diseases and dysfunctions. Goals of physical therapy include improving circulation, coordination, balance, and respiratory capacity. Exercises may be geared toward mobilizing joints and releasing contracted muscles and tendons.

Patients suffering from neurological disorders can be treated with a variety of physical therapies. For example, motor neuron damage or partial peripheral nerve damage may respond to a specific type of physical therapy called proprioceptive neuromuscular facilitation (PNF). PNF focuses on exercises that build muscle strength by applying resistance to muscle contraction. Patients who have experienced cerebrovascular accidents may undergo PNF combined with training for muscle strength, balance, and coordination. Multiple sclerosis is treated with PNF along with physical fitness training. Physical therapies for Parkinson disease focus on general physical fitness training, along with stretching exercises.

Resources

BOOKS

Putnam, Stephen C. Nature's Ritalin for the Marathon Mind. Hinesburg, VT: Upper Access Book Publishers, 2001.

Ratey, John. A User's Guide to the Brain: Perception, Attention, and the Four Theaters of the Brain. Vancouver, WA: Vintage Books, 2002.

OTHER

Effects on Neurologic Diseases and Mental Decline. Health and Age. (March 18, 2004). <http://www.healthandage.com/Home/gm=0!gc=2!gid6=2908>.

Frankenfield, Gay. "Exercise May Improve Learning and Memory." WebMD January 4, 2004 (March 18, 2004). <http://my.webmd.com/content/article/17/1676_50120.htm?lastselectedguid={5FE84E90-BC77-4056-A91C-9531713CA348>.

Lawrence, Star. "Train Your Brain with Exercise." WebMD July 28, 2003 (March 18, 2004). <http://my.webmd.com/content/article/67/79909.htm?lastselectedguid={5FE84E90-BC77-4056-A91C-9531713CA348>.

Warner, Jennifer. "Exercise Saves Brain Cells." WebMD January 29, 2003 (March 18, 2004). <http://my.webmd.com/content/article/60/66925.htm?lastselectedguid={5FE84E90-BC77-4056-A91C-9531713CA348>.

ORGANIZATIONS

Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion. Division of Nutrition and Physical Activity, 4770 Buford Highway, NE, Atlanta, GA 30341-3724. (888) CDC-4NRG ((888) 232-4674). <http://www.cdc.gov>.

The President's Council on Physical Fitness and Sports. Department W, 200 Independence Ave., SW, Room 738-H, Washington, DC 20004. (202) 690-9000; Fax: (202) 690-5211. <http://fitness.gov/index.html>.

Juli M. Berwald

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Berwald, Juli. "Exercise." Gale Encyclopedia of Neurological Disorders. 2005. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

ex·er·cise / ˈeksərˌsīz/ • n. 1. activity requiring physical effort, carried out esp. to sustain or improve health and fitness: exercise improves your heart and lung power. ∎  a task or activity done to practice or test a skill: there are exercises at the end of each chapter to check comprehension. ∎  a process or activity carried out for a specific purpose, esp. one concerned with a specified area or skill: an exercise in public relations. ∎  (exercises) ceremonies: graduation exercises. 2. the use or application of a faculty, right, or process: the free exercise of religion. • v. [tr.] 1. use or apply (a faculty, right, or process): anyone receiving a suspect package should exercise extreme caution. 2. [intr.] engage in physical activity to sustain or improve health and fitness; take exercise: she still exercised every day. ∎  exert (part of the body) to promote or improve muscular strength: raise your knee to exercise the upper leg and hip muscles. ∎  cause (an animal) to engage in exercise: she exercised her dogs before breakfast. 3. occupy the thoughts of; worry or perplex: the knowledge that a larger margin was possible still exercised him. DERIVATIVES: ex·er·cis·a·ble / -əbəl/ adj.

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"exercise." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

exercise (eks-er-syz) n. any activity resulting in physical exertion that is intended to maintain physical fitness, to condition the body, or to correct a physical deformity. Exercises may be done actively by the person or passively by a therapist. aerobic e. an exercise intended to increase oxygen consumption (as in running) and to benefit the lungs and cardiovascular system. isometric e. an exercise in which the muscles contract but there is no movement; this is induced when a limb is made to push against something rigid and is designed to improve muscle tone. isotonic e. an exercise in which the muscles contract and there is movement, but the force remains the same; this improves joint mobility and muscle strength.

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"exercise." A Dictionary of Nursing. 2008. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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Exercise

EXERCISE

To put into action, practice, or force; to make use of something, such as a right or option.

To exercise dominion over land is to openly indicate absolute possession and control.

To exercise discretion is to choose between doing and not doing something, the decision being based on sound judgment.

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"Exercise." West's Encyclopedia of American Law. 2005. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

exercise employment, practice XIV; task prescribed for training or testing; religious observance XVI. — (O)F. exercice — L. exercitium, f. exercēre keep busy or at work, practise, train, vex, f. EX-1 + arcēre shut up, keep off, restrain, prevent.
Hence vb. XIV.

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T. F. HOAD. "exercise." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

exercise Increased muscular activity, which results in an increase in metabolic rate, heart rate, and oxygen uptake. Exercise also causes an increase in anaerobic respiration in order to compensate for the oxygen debt, which results in a build-up of lactic acid in the tissues.

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"exercise." A Dictionary of Biology. 2004. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

exercise.
1. An instr. passage purely for technical practice and with little or no artistic interest.

2. In the 18th cent., a kbd. suite such as D. Scarlatti's early sonatas, pubd. as Esercizii.

3. Comp. submitted by candidates for certain univ. mus. degrees.

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MICHAEL KENNEDY and JOYCE BOURNE. "exercise." The Concise Oxford Dictionary of Music. 1996. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

exercise: see physical fitness.

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"exercise." The Columbia Encyclopedia, 6th ed.. 2016. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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exercise

exercise •excise • queen-size • laicize •Anglicise, Anglicize •polemicize • classicize • fanaticize •elasticize • poeticize • parenthesize •mythicize •photosynthesize, synthesize •synopsize • apotheosize • emphasize •circumcise • exercise • metastasize •hypostasize •affranchise, enfranchise, franchise •fetishize • alphabetize • concretize •poetize • palletize • pelletize •unitize • remonetize • syncretize •securitize • synthetize • robotize •narcotize •anagrammatize, epigrammatize, melodramatize, overdramatize •emblematize, lemmatize •legitimatize • dogmatize • aromatize •problematize • automatize •bureaucratize • advertise •telepathize • televise •collectivize, objectivize •relativize • supervise • improvise

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"exercise." Oxford Dictionary of Rhymes. 2007. Encyclopedia.com. 26 Jun. 2016 <http://www.encyclopedia.com>.

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