Gymnastics, like many sports, requires physical training that builds the overall fitness of the athlete. Although the concept may be stated in different ways, the tradition definition of physical fitness, when assessed from the perspective of the health and the function of the body, includes elements of strength, power, speed, endurance, and flexibility. Balance, together with agility and motor control, is one of the essential components necessary to produce superior athletic performance. Balance is a combination of innate sense and the development of combined physical and mental training. Balance is fundamental to gymnastic success, no matter how otherwise skilled and fit the athlete may be. Balance is the achievement of physical harmony in both movement and stationary positions; a gymnast must incorporate the notion of balance into every aspect of the execution of every routine.
Inherent to the development of balance in any gymnastics routine is an understanding of the body's center of gravity and its importance to fluid movement. The determination of the precise center of gravity will make the performance of aerial movements more efficient, particularly those involving a 360° rotation of the body. The center of gravity in an athlete is defined as the point at which the body will rotate if no other external forces are applied. The physical structures of men and women vary due to the different position and relative width of women's hips to their femur length; for this reason a woman's center of gravity is slightly lower on the body than that of a man.
The repetition that is at the heart of gymnastics training assists the athlete in sustaining balance through a routine. The bodily mechanism of muscle memory, also known as proprioception, is the ability of the body to understand and coordinate each part of the body, relative to each other, without reference to the traditional senses of sight, sound, smell, taste, and sight. As a gymnast understands through repetition where all of the musculoskeletal joints are positioned as a movement is performed, the body will achieve balance without reliance upon the five senses. The function of the inner ear and vestibular system are well understood as being connected to the proprioception system; an inner ear infection can cause significant difficulty for a gymnast for this reason.