Muscle: Use It or Lose It Until You Use It Again

It turns out we may be able to “bank” muscular training benefits from our younger selves to help maintain muscular strength as we age. One caveat: We must train again to reap those benefits.

A new theory on what happens when muscles atrophy is gaining ground. Researchers generally agree that when muscle fibers increase in size, the myonuclei increase in number. And scientists used to think that when muscle fibers atrophied, those myonuclei were lost, too. New research suggests, however, that even when muscle fibers atrophy, the myonuclei are not lost.

This new research is based on studies with rodents and insects, but scientists believe it sheds light on what may happen in human muscles. Mini-review author Lawrence M. Schwartz, PhD, integrated science professor at the University of Massachusetts in Amherst, noted, “The retention of ‘surplus’ nuclei during atrophy confers a distinct advantage for the individual since skeletal muscles frequently undergo cycles of atrophy and hypertrophy in response to environmental conditions such as food availability. The ability to recover quickly by utilizing pre-existing myonuclei may serve an important role in adaptation and help explain the phenomenon of ‘muscle memory.’”

These findings support encouragement of muscle training when young—particularly during adolescence, when muscle growth is enhanced—to potentially slow the effects of muscle loss from aging. Another implication relates to competitive sports and banned drugs. People who use steroids to stimulate hypertrophy and accordingly add new myonuclei will retain the benefits of these additional myonuclei even after they stop taking steroids.

The review is available in Frontiers in Physiology (2019; 9 [1887].