Reversibility
This principle states that gains made through training are lost when training stops (Izquierdo et al, 2007). Gains in fitness and strength are reversible and if we do not consistently apply a training stimulus, the body does not see any reason to keep these adaptations as it is not being stressed. The body will then start to revert to its original pre-training state. De-training will occur quicker if only a short period of training occurred and was then stopped. For example, if a short pre-season period of training occurs (e.g. a six-week period) and should little or no strength training take place in-season, then the gains made during pre-season may be gradually lost such that the player returns to baseline levels at an early point in the in-season. Studies have shown that when strength training is maintained at a reduced frequency of training during the in-season then gains in strength can occur (Kraemer et al, 2003, Izquierdo et al, 2007, Weiss, 1988).