“Go heavy or go home!” It’s a common catchphrase of diehard lifters that resonates well with both those immersed in the trenches of the iron battlefield and perched atop the ivory towers of academia. Researchers and lifters alike have long espoused the use of relatively heavy weights and lower reps for more muscle and strength. However, if your intention is to build bigger muscles rather than simply impress other people in the weight room with the amount of weight you lift, then you might want to extract a few of those extra plates and keep reading.
Heavier weight or “load” is usually expressed as percentage of a person’s strength for one maximum repetition (1RM). Traditionally, heavier loads have been accepted in being more conducive to hypertrophy since they are capable of recruiting and subsequently activating a greater proportion of type II muscle fibers – which possess superior growth potential to their type I counterparts.
Contrary to long held beliefs, mounting literature suggests that high-repetition training with lower weight can result in a considerable amount of muscle fiber recruitment and hypertrophy. In fact, recent research suggests that lighter weights performed for as many as 30 repetitions or more may be just as effective as heavy loads and low reps.
The Science of High Reps
Several studies have shown that executing a greater number of repetitions, if performed to the point of muscle failure, can be equally as effective as traditional heavy load, low-rep training in stimulating muscle protein synthesis rates and increasing the size of both type I and II muscle fibers.
A 2010 study published in the Journal of Applied Physiology demonstrated that a single bout of resistance exercise performed with a mere 30% 1RM performed to muscle failure was equally as effective in stimulating muscle protein synthesis rates as loads of 90% 1RM also taken to failure. Additionally, the lighter weight high-rep programs showed a more prolonged anabolic response than a heavy load program in the 24 hours period after training.
In the same study, the average size of both type I and II muscle fibers increased equally with heavy and light loads, suggesting that both fiber types were recruited during training and to a roughly equal extent. It also appears that as repetitions at lighter loads are continued, the point of muscular failure may be what’s responsible for activating additional motor units which means that reaching the point of failure with lighter loads may be a necessity in order to elicit similar muscle fiber activation as when training with heavier loads. This suggests that intensity of effort and not the amount of weight may be the more important consideration in a training program.
More recently, one study used previously trained subjects to compare a low-load routine, which consisted of 25-35 repetitions (approximately 30-50% RM) performed to failure with a high-load routine where 8-12 repetitions (approximately 70-80% RM) were performed. The low load protocol significantly increased muscle hypertrophy similar to that of the traditional higher load “hypertrophy” training.
It has been proposed that the muscle building potential of low-loads could be due to added time under muscular tension and ensuing metabolic stress as well as greater stimulation of the often-underestimated growth capacity of type I muscle fibers.
Practical Application
Extrapolating from the aforementioned studies, it appears that training for more muscle is not entirely dependent on the number of “wheels” on the bar. And while lighter loads may not do your ego justice, they can elicit a significant muscle building response.
This is welcome news for older lifters and those who suffer with “wear and tear” injuries, which prohibit them from training with heavy loads. Lighter load, high-rep training can be employed as a way to reduce stress to sore or aching joints that sometimes result from heavier training, and provide a viable alternative for anyone with musculoskeletal injuries or other orthopedic considerations.
In the end, claims of the superiority of a specific load or number of repetitions in a set as the optimal way to increase muscle size have not been unequivocally proven. But based on recent evidence, bodybuilders and strength athletes with a goal of maximizing muscle hypertrophy should embrace the use of lighter weight, higher repetition training as a legitimate strategy to build muscle.
