The mechanism of muscle retention

Prof. Eli Carmeli

Abstract

Background: Muscle retention or memory is a relatively new feature compared with all the characteristics ascribed to the cell (the "fiber") of the striated skeletal muscle. As a result of training to develop muscle power/strength, the muscle fibers undergo a process of adjustment/ adaptation. The question is whether this adjustment/adaptation is retained or alternatively, the muscle loses the memory of this adjustment/adaptation as soon as the person stops exercising,.

Methods: In an attempt to find evidence of muscle memory, the databases of PubMed, CINAHL, and Google were searched for the following keywords: muscle memory, atrophy, exercises, and adult stem cells. Findings included studies conducted in modeling laboratories (in vitro) and studies conducted on animals and humans (in vivo).

Objective: To review the professional literature and substantiate the argument that also striated muscle fiber demonstrates a capacity for

retention /memory.

Results: Following strength/ power training, the sarcolemma converges with the basement membrane ofadult stem cells located near the

 muscle fiber (the process is referred to as syncytium). As a result, the addition of muscle-fiber nuclei leads to increased production of ribosomes and proteins, thus increasing the fiber's weight and size.

Discussion: The syncytium, i.e., the multinucleated cell that results from the fusion of muscle fiber with adult stem cells following strength/power training, is evidence of the muscle's ability to undergo adjustment/adaptation. However, even when there is no further exposure to strength training, the number of nuclei in the hypertrophic muscle fiber remains unchanged for a period of 10-25 years. This suggests that there is learning and retention of muscle mass. Moreover, if muscle strength/power training is resumed, the myofibers will develop muscle strength and power more quickly and with greater intensity, benefitting from retention of the prior memory, when the myofibers fused with adult stem cells and "'stole" the nuclei that now make it possible to build higher quality muscle mass more quickly.

This fact is important, as it can stimulate and encourage people to engage in training to develop muscle strength/power and mass, which can be retained for "a rainy day".

Key words: muscle retention, muscle memory, adult stem cells, hypertrophy,