Warming up is a process which elicits the acute physiological changes that prepare the organism for strenuous physical performance. To gain the greatest benefit from the warming-up procedure, the exer­cises should imitate as closely as possible the movements which are to be used in the event.

Warming up reduces the viscosity of a muscle, its resistance to its own movement. It improves performance and prevents injury in vigorous activities by two essential means:

1. A rehearsal of the skill before competition commences fixes in the athlete's neuromuscular coordinating system the exact nature of the impending task. It also heightens his kinesthetic senses.
2. The rise in body temperature facilitates the biochemical reactions supplying energy for muscular contractions. Elevated body temperature also shortens the periods of muscular relaxation and aids in reducing stiffness. 

As a result of these two processes, there is an improvement in accuracy, strength and speed of movement, and an increase in tissue elasticity which lessens the liability to injury.

No fighter uses his leg violently until he warms it up carefully. The same principle is equally applicable to any muscles that are to be used so vigorously. The duration of the warm-up period varies with the event. In ballet, the dancers spend two hours before the performance, commencing with very light movements and gradu­ally increasing the intensity and range of motions until the moment before their appearance. This, they feel, reduces the risk of a pulled muscle which would destroy the perfection of their movements.

The athlete of more advanced years tends to warm up more slowly and for a longer time. This fact may be due to greater need for a longer warm-up period, or it may be because an athlete tends to get smarter as he gets older.