Training one arm can improve strength and decrease muscle loss in the other arm - without even moving it, suggest the findings of new research from Edith Cowan University (ECU). The findings could help to address the muscle wastage and loss of strength often experienced in an immobilized arm, such as after an injury, by using eccentric exercise on the opposing arm. In eccentric exercises, the contracting muscle is lengthening, such as when lowering a dumbbell in bicep curls, sitting on a chair slowly or walking downstairs. Previous research has shown these exercises are more effective at growing muscle than concentric exercises, which are muscle shortening such as when lifting a dumbbell or walking upstairs. The study involved 30 participants who had one arm immobilized for a minimum of eight hours a day for four weeks. The group was then split into three, with some performing no exercise, some performing a mix of eccentric and concentric exercise, and the rest performing eccentric exercise only. Professor Nosaka said the group who used a heavy dumbbell to perform the only eccentric exercise on their active arm showed an increase in strength and a decrease in muscle atrophy, or wastage, in their immobilized arm. Professor Nosaka also said this type of training is useful for athletes who can begin post-injury recovery sooner.