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“Like riding a bike” serves as a metaphor for the incredible way in which our bodies retain movement skills. Most discussions of muscle memory do not reference the muscles directly but the recollection of a synchronized movement pattern residing in motor neurons, which command our muscles.
However, recent studies have revealed that our muscles themselves possess a memory for movement and activity.
As we engage a muscle, the action might seem to start and finish, yet all these subtle changes continue to unfold within our muscle cells. The more frequently we engage in movement, like cycling or other forms of exercise, the more those cells begin to remember that particular activity.
As we engage a muscle, the action might seem to start and finish, yet all these subtle changes continue to unfold within our muscle cells.
Everyone is aware through experience that a muscle enlarges and strengthens with regular exertion. As the trailblazing muscle researcher Adam Sharples—a lecturer at the Norwegian School of Sport Sciences in Oslo and a former professional rugby athlete in the UK—explained to me, skeletal muscle cells are distinctive in the human body: They are elongated and thin, resembling fibers, and contain several nuclei. The fibers increase in size not through division but by enlisting muscle satellite cells—dormant stem cells specific to muscle that become active in reaction to stress or injury—to provide additional nuclei and facilitate muscle growth and repair. These nuclei often remain in the muscle fibers for an extended period, even after inactivity, and there is indication that they may assist in hastening the return to growth when training resumes.
Sharples’s investigations concentrate on what is termed epigenetic muscle memory. “Epigenetic” pertains to alterations in gene expression driven by behavior and environment—the genes themselves remain unchanged, but their functionality does. Generally, exercising activates genes that facilitate easier muscle growth. For instance, when lifting weights, small molecules known as methyl groups detach from the exterior of certain genes, increasing their likelihood to activate and generate proteins that impact muscle growth (also termed hypertrophy). These modifications endure; if you resume weight lifting, you will gain muscle mass more rapidly than previously.
In 2018, Sharples’s muscle laboratory was the first to demonstrate that human skeletal muscle has an epigenetic memory of growth post-exercise: Muscle cells are prepared to respond more quickly to subsequent exercise, even following a prolonged (and perhaps even lasting) hiatus. In simpler terms: Your muscles remember how to perform it.
Further research from Sharples and colleagues has replicated these findings in mice and elderly humans, providing additional corroborative evidence of epigenetic muscle memory across different species and advancing age. Even as muscles age, they retain the ability to remember workout routines.
Currently, Sharples points to fascinating new findings indicating that muscles also retain memories of atrophy—and that younger and older muscles recall this differently. While youthful human muscle appears to possess what he describes as a “positive” memory of wasting—“in that it rebounds effectively after an initial phase of atrophy and demonstrates no greater loss during a subsequent atrophy period,” he clarifies—aged muscle in rats seems to exhibit a more marked “negative” memory of atrophy, appearing “more prone to greater loss and a more intense molecular reaction when muscle wasting is repeated.” Essentially, younger muscle typically recovers from periods of muscle loss—“overlooking” it, so to speak—while older muscle is more reactive to it and may be at an increased risk for further loss in the future.
Disease can also contribute to this form of “negative” muscle memory; in a study involving breast cancer survivors more than ten years post-diagnosis and treatment, participants exhibited an epigenetic muscle profile akin to that of individuals substantially older than their chronological age. Yet, intriguingly: Following five months of aerobic training, participants were able to restore the epigenetic profile of their muscle to resemble that of muscle found in a control group of healthy women matched by age.
What this illustrates is that “positive” muscle memories can counterbalance “negative” ones. The key takeaway? Your muscles possess a form of intelligence. The more you engage them, the more they can utilize it to become a lasting advantageous resource for your body in the future.
Bonnie Tsui is the author of On Muscle: The Stuff That Moves Us and Why It Matters (Algonquin Books, 2025).
