These new proteins can increase the size of the cells within the muscle to make them larger, a process called hypertrophy. The common convention surrounding gains in skeletal muscle size and strength is that heavy weights are needed. In contrast, lifting lighter weights are thought to be required to induce muscular endurance and not to promote growth. However, it has previously been shown in untrained men that lifting lighter weights results in similar gains in muscle mass and strength as lifting heavier weights. The purpose of this study is to examine how performing resistance training of different intensities (light or heavy weights) affects the degree of muscle growth and strength gain in individuals who are already resistance training.