Muscle memory refers to the observation that when a person begins lifting weights after a prolonged layoff, it is much easier to return to his or her previous levels of size and strength than it was to get there the first time around. A hypothesis has been proposed that the key to muscle memory lies in the central nervous system, or, in other words, a large part of achieving the original gains was due to an increase in muscle coordination. It is thought that this coordination is retained and facilitates regaining the strength and subsequent muscle size after a layoff.
Researchers from Texas A&M University investigated the effects of previous strength training and retraining following a long-term period of no training on muscle mass and contractile properties. Rats were forced to climb a ladder with 50–100% of their body weight tied to their tail for eight weeks. Then training was stopped for 20 weeks, and then another eight-week period of training was conducted.
As expected, retraining led to a significant increase in muscle size, surpassing the results of the first training period. Interestingly, the contractile properties were not significantly altered by the original training period.
Muscle memory is evidenced by a rapid regain of previous gains in muscle size; however, there was no significant evidence that muscle memory was a result of long-term changes in the nervous system or contractile properties of the muscle.
Although this study did not prove that muscle memory is a function of the nervous system, it does reinforce the notion that long breaks from training do not mean lost opportunities for muscle growth. It could very well be that extended breaks from training (i.e., four to six weeks) could actually bring about changes in the muscle that resensitize it to the training stimulus. This is the principle behind HST’s Strategic Deconditioning. If you have been training consistently and eating well and yet have not been experiencing gains for a long time, it could be that a layoff is what you need to bust through that plateau.