For muscle building, lighter weights are just as effective as heavier weights. Strange but true. And proven by a study at McMaster University, where researchers recruited two groups of experienced weight lifters- all of them men. For 12 weeks, one group lifted lighter weights (up to 50 per cent of maximum strength) for sets ranging from 20 to 25 repetitions. The other group lifted heavier weights (up to 90 per cent of maximum strength) for eight to 12 repetitions. Both groups lifted to the point of failure. A McMaster news release reports that when researchers analyzed muscle and blood samples, they found that gains in muscle mass and muscle fibre size were virtually identical. They also found that none of the strength or muscle growth was related to testosterone or growth hormone.