Sky diving is the sport form of parachuting, an activity defined as the controlled descent of a person to the surface of the earth from an aircraft, using a parachute to control the rate of descent. Sky diving is often grouped with sports such as bungee jumping and para-gliding, activities which are often described as the aerial extreme sports.
The history of parachute jumping pre-dates the modern concept of extreme sport by several hundred years. Leonardo da Vinci (1452–1519), the noted Renaissance inventor and artist, designed a parachute intended for use in the rescue of persons from burning buildings. A number of French balloonists experimented with parachutes from heights of over 2,000 ft (600 m) beginning in the late 1780s.
With the advent of powered aircraft in the early part of the twentieth century, parachuting became a important component of military troop deployment, tactics, and aircrew safety. The paratrooper is a specialized soldier used in a wide number of combat roles in present day military operations.
The first sport parachuting competition was held in Yugoslavia in 1951. Sky diving, like most extreme sports, places a far greater emphasis upon the personal experiences of the participant, as they seek to achieve a personal goal, rather than focusing on the attainment of a competitive objective. Sky divers have established a number of records that are a testament to human endurance. The most notable example is that of the parachute jump from the greatest height ever recorded. In 1960 Col. Joseph Kittinger of the United States Air Force traveled 102,800 ft (31,000 m), a fall that lasted approximately 4.8 minutes, in which Kittinger reached speeds approaching 700 mph (1,100 km/h) over a desert in New Mexico.
Sky diving requires primary importance to be placed upon the safety of every participant. In the United States, a prospective skydiver must be a minimum of 18 years of age (16 years of age if they have the permission of a parent or guardian to make a jump). The subject must also obtain a certificate of physical fitness from a physician, and all sky divers must complete a training program known in most jurisdictions as a first jump course. The first jump will generally take one of two training formats, a tandem free fall jump, or an instant opening/static line jump. In a tandem free fall jump, the student and instructor jump together from the aircraft at an altitude of approximately 10,000 ft (3,000 m), attached to the same parachute system. The two persons enter free fall (where they are pulled without restriction towards the earth by the force of gravity) for approximately 30-50 seconds, when the parachute is activated. In a instant opening jump, the student jumps and the parachute opens immediately upon the student exiting the aircraft.
A significant aspect of sky diving is the execution of group parachute jumps, where the participants seek to create different shaped formations in the air as they fall. The group formation divers wear skin-tight jump suits to reduce the effect of drag on their bodies as they fall through the air. During the period prior to the activation of their parachutes by the sky divers, the formation moves in a group free fall. Drag is the force created upon any body moving through the air; skydivers will also reduce the effect of drag in the creation and maintenance of the shape of the desired formation during descent, by altering the profile of their bodies as they descend. These sky divers will reach speeds of approximately 100 mph (190 km/h) prior to the deployment of their parachutes.
At several locations through out the world, wind tunnels are utilized by sky divers to simulate the conditions experienced by a skydiver as they descend in free fall.
Sky divers often describe their sport with any number of adjectives that convey the excitement of the rush towards the earth's surface; exhilarating and breath-taking are two that are commonly employed. The determination of the physical fitness of the participants centers on the healthy function of the subject's cardiovascular and cardiorespiratory systems. The risks associated with sky diving are more often identified with substandard safety practices both in flight and at the drop zone, such as the proximity of trees or power lines to the descending sky diver. In the United States, there are approximately 15 sky diving fatalities for every one million jumps annually.
An important physical skill learned by sky divers is the absorption of the forces generated on landing. A favored technique is the entering into a sideways roll immediately upon impact, with the hands and arms kept close the sky diver's torso. This technique is known as the parachute roll; if the landing forces are not absorbed effectively, the skydiver risks serious injury to the feet and lower legs. If the skydiver is overweight, the risk of forces at impact causing injury are magnified accordingly.