Pumping Iron? A Lighter Load May Give Better Results

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Enough with the grunting and groaning at the gym already. New research this week in PLoS One shows that, to build muscle, it’s more effective to lift a lighter weight many times than to lift a heavy load that you can only manage five or 10 times.

Researchers at McMaster University in Canada asked a group of young men to lift the heaviest weight that they could (doing just one lift) on a unilateral leg-extension machine. Some of those men were then assigned, in the weeks that followed, to exercise doing sets of leg extensions with a weight that was 90% of their max possible weight, while others were assigned to do sets with just 30% of their max weight. The catch: both groups were supposed to keep lifting until they could no longer get a full range of muscle motion when they attempted a lift — until their muscles, in other words, were too tired to continue.

Members of the lighter-load group were consistently able to perform greater total exercise  volume — that is, greater load X repetitions. More importantly, muscle biopsies and blood samples revealed that “low-load high volume resistance exercise is more effective in inducing acute muscle anabolism,” the researchers write.The low-load group had higher rates of myofibrillar protein synthesis at 24 hours after exercise.

This news may be helpful for recreational gym-goers who want to get more out of their weight routines. But the finding may have more important implications for patient rehabilitation, study co-author Stuart Phillips said in a statement. Elderly people, or people recuperating after an injury, may be intimidated when feeling weak by the thought of having to lift heavy weights. A lighter load can be perfectly effective for building muscle mass, the new research shows — provided you keep lifting long enough.