We apply this principle when" your body adapts to the activity and the exercise becomes to easy." Overload?
specificty?
Progression?
Reversibility?​

Progression

because its not reversibility that is if you stop working out completely

Explanation:

recent brain research has shown some surprising benefits as a result of formal musical training. learning to play a musical instrument appears to develop parts of the brain that can even influence academic results. the studies indicate that the earlier a child begins training, the more benefits there are. one such study showed that children who began musical studies before the age of seven had a more developed brain in the region where language production and auditory processing take place. scientists believe there is mounting evidence to show that early musical training can improve brain function.

explanation: