New research from Edith Cowan University (USA) has revealed that one arm training can improve strength and decrease muscle loss on the other arm, without even moving it.

The findings, published in the journal Scandinavian Journal of Medicine & Science in Sports, could help address the muscle wasting and loss of strength often experienced in an immobilized arm, such as after injury, by using use of eccentric exercises on the opposite arm.

In eccentric exercises, the muscle that contracts lengthens, such as when lowering a dumbbell on the biceps, slowly sitting in a chair, or walking down stairs. Previous research has shown that these exercises are more effective for muscle growth than concentric exercises, in which the muscle shortens, such as when lifting a barbell or climbing a ladder.

According to the authors of this study, their results challenge conventional rehabilitation methods and could improve outcomes for patients after injury and stroke. “I think this could change the way we approach rehabilitation of people who have temporarily lost the use of an arm or a leg. By starting rehabilitation and exercise on the uninjured limb right away, we can prevent exercise-induced muscle damage in the other limb and also build strength without moving it at all, “explains study leader Ken Nosaka.

The study

The study involved 30 participants who had one arm immobilized for a minimum of eight hours a day for four weeks. The group was divided into three, some did no exercise, some did a mixture of eccentric and concentric exercises, and the rest did only eccentric exercises.

The group that used a heavy weight to perform only eccentric exercise on their active arm showed increased strength and decreased muscle atrophy, or wasting, in their immobilized arm. Participants who did the eccentric exercise had the greater increase in strength on both arms, so it has a very powerful cross transfer effect.

This group also had only one 2% muscle waste in their immobilized arm, compared to those who did not exercise, who had a 28% loss of muscle. This means that for people who don’t exercise, they have to regain all that muscle and strength again.