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• Posted March 7, 2023

Arm in a Cast? Exercising the Other Arm Can Curb Muscle Loss

You can keep an arm in a cast from wasting away, researchers say, by working out your free arm.

A small group of young men who performed eccentric contraction exercises with one arm -- lowering a dumbbell in a slow and controlled motion -- saw a 4% strength improvement in the other arm, even though it was immobilized by a cast at the elbow.

Another group assigned to perform concentric contraction exercises -- lifting a dumbbell -- only lost about 4% of muscle strength in their immobilized arm, the study results showed.

By comparison, a "control group" that did no exercises suffered a 15% decrease in their immobilized arm during the three-week study.

It was already known that gaining muscle strength in one limb through resistance training will transfer to the same muscle on the opposite side of the body, said lead researcher Ken Nosaka. He is head of exercise and sports science at the Edith Cowan University School of Medical and Health Sciences, in Australia.

"This is known as the cross-education effect,"Nosaka said in a university news release. "The key aspect of this study is one particular type of muscle contraction proved most effective."

For the study, 36 young men had their non-dominant arm immobilized by a cast at their elbow joint for three weeks.

They were then split into three groups evenly: dumbbell lifting (concentric); dumbbell lowering (eccentric); and no exercise.

Those assigned strength training had six sessions over three weeks, with the weight increasing as their arm gained strength.

When the cast was removed, results showed that lowering exercises best maintained strength in the arm that had been immobilized.

The exercises also helped muscle size. There was no decrease in muscle size for the eccentric group, versus a 4% decrease in the concentric group and a 12% decrease in the control group.

Further, the exercise protected against muscle damage. All participants were asked to lower a dumbbell 30 times with their immobilized arm after the cast was removed.

The control group showed very severe muscle soreness and strength loss after the exercise, the researchers said.

But the eccentric group had a protective effect from exercise that reduced their peak muscle soreness by 80% compared to the control group and 40% compared to the concentric group.

"It is important to investigate whether this latest study's results are replicated for other muscles and whether eccentric resistance training is effective when dealing with immobilization in real injuries, such as ligament sprains or tears, bone fracture, and post-surgery,"Nosaka said.

"However, health care providers can recommend resistance training -- and eccentric contractions in particular -- to minimize the negative effects of immobilization and hopefully lessen its impact on people's lives,"he added.

The new study was published recently in the journal Medicine & Science in Sports & Exercise.

More information

Frontiers has more about eccentric exercise.

SOURCE: Edith Cowan University, news release, March 1, 2023