Many fitness experts maintain that exercisers must work within the 8- to 12-repetition range to initiate muscle hypertrophy. However, a study published in PLoS ONE (2010; 5 [8], 1–10) suggests that low-load, high-volume strength training can also impact muscle growth. Researchers from McMaster University in Hamilton, Ontario, studied 15 men as they performed four sets of unilateral leg extensions at 90% 1-RM and 30% 1-RM. The subjects were instructed to work until failure. The study authors reported that at 90% 1-RM, subjects usually managed 5–10 repetitions before failure; at 30% 1-RM, failure set in at about 24 repetitions. To control nutrition intake, on the intervention date the participants were each given a liquid meal made up of 61% carbohydrate, 15% protein and 24% fat. The researchers then analyzed protein muscle synthesis of the subjects for 24 hours postintervention.

“We report for the first time that low-load high volume resistance exercise is more effective at increasing muscle protein synthesis than high-load low volume resistance exercise,” stated the study authors. The authors also stated that the 90% 1-RM showed increased protein synthesis up to 4 hours postexercise; however, 30% 1-RM showed elevated protein synthesis up to 24 hours postexercise. The ultimate goal, added the authors, is to work until muscular fatigue.

IDEA presenter Michol Dalcourt suggests that professionals investigate a bit further when considering working with high repetitions. “Muscle is not the only viable structure to create movement and adapt to stress,” he says. Collagen, the fundamental element of fascia, must also be considered. “[Collagen] responds to external loading by laying down more of itself along lines of stress,” says Dalcourt. “If that line of stress is repeated and in only one direction—as in this study—then the fascia is not getting the vector variation it needs to be healthy.” Muscles may grow, adds Dalcourt, but repetitions within the same range of motion can limit functionality.