Which of the following is NOT a principle of training?

Overload is a foundational training principle stating that the body must be stressed beyond its current level to produce adaptation.

Specificity is a recognized training principle stating that adaptations are specific to the type of training performed.

Reversibility (also called detraining) is a recognized principle stating that fitness gains are lost when training stimulus is removed.

The established principles of training are Overload, Specificity, Reversibility, Progression, and Individuality. Concentration describes a mental approach to resistance exercise (the mind-muscle connection) and is not categorized as a principle that governs how the body adapts to systematic training stress.