Force and Fatigue

When you do forced reps, a training partner helps you complete a set after you’ve reached momentary muscular failure. The partner should provide only enough assistance to enable you to complete the set’you, not your training partner, should be lifting the weight, though too often the reverse is true.

Few exercise techniques give you a level of intensity comparable to that of forced reps, since it takes you past the point of muscular failure. You’re working the muscle down to the bone. But, given all that pain and intensity, how do forced reps affect anabolic hormones, such as testosterone and growth hormone, during training? Conversely, what about the effects on cortisol, the primary catabolic hormone?

Those questions were the focus of a recent study.1 It featured 16 male athletes engaged in either a maximum-reps routine or a forced-reps routine. The maximum-reps routine involved a standard style of training, with the subjects doing four sets of leg presses, two sets of squats and two sets of leg extensions’for a maximum of 12 reps per set. They rested two minutes after each set and four minutes after completing each exercise. With the forced-reps protocol they used a weight heavier than they could lift for 12 reps, thus requiring forced reps to complete the set. Obviously, the training intensity was much higher than with the standard approach.

Both types of training led to considerable increases in total serum testosterone, free testosterone, cortisol and growth hormone. The growth hormone and cortisol levels were higher with the forced-reps routine; testosterone levels were similar in both groups. Forced reps also elicited a greater decrease of maximum muscular force than the standard style of training.

Growth hormone and cortisol are related to exercise intensity. Because forced reps produce a higher rate of training intensity, it isn’t surprising that the forced-reps group produced greater levels of both GH and cortisol. GH release is related to the amount of lactic acid released during training, and in this study forced reps produced the most lactic-acid release.

The greater loss of muscle power induced by the forced reps implies that the training style requires more recovery. Most bodybuilders have found that out empirically, and they don’t use forced reps on every set. The technique is more frequently used by advocates of high-intensity training, since HIT features less total training volume along with more rest between sessions’you don’t have to do much of that type of training to get an appreciable training effect.

The study authors, while noting that forced reps produce higher levels of growth hormone, aren’t sure of the technique’s anabolic effects. According to the experience of most bodybuilders who have correctly used forced reps as part of their training, the technique is effective for forcing muscle growth, though its severity mandates reserving it for serious trainees.

1 Ahtiainen, J.P., et al. (2003). Acute hormonal and neuromuscular responses and recovery to forced vs. maximum repetitions with multiple resistance exercises. Int J Sports Med. 24:410-418.