Muscle Strength Is in the Mind

A new study found that just imagining arm exercises created a tangible effect on the body.

“If there are jocks on one side, and it’s a confrontation, the other side, by definition, has to be nerds,” David Anderegg wrote of what he calls the “archetypal struggle” in Nerds: Who They Are and Why We Need More of Them.

Of course, there are moments—mostly in Disney musicals—when both camps lay down their footballs and their calculators and realize that really, brain and brawn aren’t mutually exclusive—that, in fact, they have more in common than they ever thought.

This is one of those moments.

In a small study recently published in the Journal of Neurophysiology, researchers found that much of muscle strength is based on brain activity, rather than on the mass of the muscles themselves. Researchers at Ohio University’s Musculoskeletal and Neurological Institute, 29 volunteers had their non-dominant arms placed in elbow-to-finger casts for four weeks. (Fifteen others acted as a cast-free control group.) Of the 29, 14 were asked to perform mental-imagery exercises five days a week, imagining themselves alternately flexing and resting their immobilized wrists for five-second intervals.

When the casts came off at the end of the four weeks, both groups had lost strength in their arms—but the group that had imagined themselves doing the arm exercises lost significantly less, measuring an average of 25 percent weaker than at the start of the study, compared to 45 percent for the group that hadn’t taken part in the mental-imagery activities.

“There’s a fair amount of evidence that you’ll activate the same parts of the brain doing imagery as you do if you’re actually doing the task itself,” explained Brian Clark, a physiology professor at Ohio University and the study’s lead author. “The basic thought is that the imagery is allowing the brain to maintain those connections.”

People “logically think that muscle strength is primarily determined by muscle size,” Clark said, but “the nervous system is integrally related to muscle performance … If you swing a golf club for the first time, you’ll likely miss the golf ball. But if you do it a hundred times, you’ll learn how to hit that ball. Well, the same thing happens when we go through periods where we don’t do tasks—we kind of forget how to do it. And so the idea is the imagery, in this case, prevents us from forgetting.”

Muscle memory, in other words, is really just memory; each part of the body has a corresponding space in the brain that can its own separate workout. “The muscles are a puppet to the nervous system,” Clark said—a line that, if the script were written by physiologists with an ear for metaphor, might have come straight out of Revenge of the Nerds.