Broken Arm? Exercising a Healthy Limb May Fight Muscle Loss in the Broken One

If you’ve ever broken your arm, perhaps this scenario rings a bell. You’re ecstatic to finally shred your plaster cage. The doctor carefully removes your cast, unveiling your now-healed limb. You look down and you’re completely taken aback by how much smaller your arm looks!

Muscle loss — or “atrophy” — occurs while wearing a cast. While atrophy is normal, it’s safe to say no one likes muscle loss and the feeling of weakness often experienced once a cast is removed. But a new study suggests there might be an effective strategy to offset muscle weakness.

Offsetting muscle weakness could be easier than you think

Most people with a broken arm forgo exercising altogether while their arm heals, but a new study shows that exercising the other arm may help offset muscle weakness.

In a study published by the Journal of Applied Physiology, graduate student Justin Andrushko and his colleagues recruited a group of 16 college students to wear casts on their left wrists for one month.

In the study, half of the students exercised their right arm day times each week, using a type of training calling “eccentric training.” In short, eccentric training lengthens the muscle during contraction and is effective for growing muscle and improving strength.

Students who didn’t train lost muscle and strength

The students’ wrists were measured in several ways before and after wearing the casts. Unsurprisingly, the student who did not train lost about three percent of their muscle volume and about 20 percent of their strength after a month of wearing the cast.

On the other hand, students who did train their right arm preserved both muscle volume and strength.

Cross-education could explain this phenomenon

The phenomenon might be explained by what is known as “cross-education” — although what causes this effect is not fully understood. One theory, however, is that small contractions (known as mirror contractions) occur under the cast. These mirror contractions may occur when the other limb is exercised, this preventing atrophy.

Although more clinical studies are needed, these exciting results may foreshadow future changes to standard rehabilitation practices.