Fitness

Why can't I bulk up?

I eat a high-calorie, high-protein diet, and I work out with heavy weights and low reps four times a week, yet I still don’t seem to be able to put on much weight. Any idea what’s going wrong?
Nathan Walsh, by email

Jason Anderson replies: There may be several reasons why you’re struggling to put on weight, which could include overtraining and poor nutrition, but the most likely reason is that you’re training for strength and not muscle growth. To stimulate muscle growth you need to fatigue as many muscle fibres as possible. When performing low reps with heavy weights the duration of the set is often too short to produce the muscle fatigue necessary to stimulate growth. Ideally you need to spend 48 seconds on each set. To achieve this you need to drop the weight a little to allow you to reach ten to 12 repetitions (two seconds up and two seconds down). To increase muscle fatigue you also need to increase the number of sets you perform. As a rough guide, do nine to 12 sets per large muscle group and six to nine sets per small muscle group.