Bad shoulder? Exercising just one arm still increases strength in the other, study shows

JOONDALUP, Australia — How would you like to cut your workout routine in half? Researchers at Edith Cowan University say training just one arm still provides benefits for the other arm even if you never move it once. The study is providing new evidence that exercise for people who have suffered an injury is helpful in avoiding muscle loss while a limb is inactive.

The Australian team studied 30 participants who had one arm immobilized at least eight hours a day for a month. Researchers reveal just doing eccentric exercises on one arm can significantly improve the health of your other limb when compared with doing no exercises at all.

“Participants who did eccentric exercise had the biggest increase in strength in both arms, so it has a very powerful cross-transfer effect,” ECU’s Prof. Ken Nosaka says in a media release.

“This group also had just two percent muscle wastage in their immobilized arm, compared with those who did no exercise who had a 28 percent loss of muscle. This means that for those people who do no exercise, they have to regain all that muscle and strength again.”

Which exercises prevent muscle loss when your limb is immobilized?

The study focuses on movements which can improve strength and combats muscle loss. Researchers find eccentric exercises, which lengthen contracting muscles, provide tremendous benefits for people working out one arm or one leg.

These include lowering a dumbbell during bicep curls, sitting on a chair slowly, or walking downstairs. Previous studies find these movements are more successful when it comes to growing muscle than concentric exercises. These exercises, lifting dumbbells and walking up stairs, shorten the contracting muscle.

Study authors split the 30 participants into three groups, who either engaged in no exercise, eccentric exercises, or both eccentric and concentric exercises. Professor Nosaka says the group using a heavy dumbbell for eccentric movements only successfully increased strength and decreased muscle atrophy in their immobile arm.

Improving rehab workouts

Researchers say further research on other arm muscles and movements can help improve how trainers build rehabilitation programs for patients.

“In this study we focused on the elbow flexors as this muscle is often used as a model to examine the effects of immobilization on strength and size, and of course it is an important muscle for arm movement,” Nosaka says.

“In the future, we hope to look at how eccentric exercise can help improve motor function, movement and fine muscle control, which is particularly important for stroke and rehabilitation patients.”

The study appears in the Scandinavian Journal of Medicine and Sports Science.