Training for Muscle Size. A hypertrophy, or bodybuilding, trianing program involves using lighter loads, which allows the athlete to perform more repetitions than is typical of a strength training program, but heavy enough to elicit concentric or eccentric contraction failure (inability of the muscle to shorten or lengthen under control) within 6 to 12 repetitions. The rest period is of short to moderate duration, since it is important to begin the next set of exercise before full recovery has been achieved. Also, it is not unusual for the athlete to perform 12 to 20 (or more) successive sets that focus on one muscle group during a single training session. This higher overall training volume coupled with a moderate relative intensity (expressed as a percent of 1RM), although lower than for strength training, appears to be optimal to increas muscle girth...