Following extinction, a conditioned response can be learned again more quickly than it was learned originally. this process is called

This is termed as spontaneous recovery.

In Psychology, the area of study where behaviors and learning are the focus is termed as behaviorism. Behaviorists focuses on discerning behaviors that are favorable and reinforced rather than those unconditioned and punished.
One type of behavioral conditioning called operant conditioning recognizes punishment and reinforcement.

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.