What is the maximum number of stimulating reps that we can do in a workout for a muscle group?

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Currently, the maximum volume that strength-trained lifters should use for optimal gains is unclear. As a result, there is vigorous debate ongoing between proponents of very high volumes and those who advocate moderate volumes. Nevertheless, we can make sense of the literature quite easily if we are prepared to dig into the details of each study, and look at what was done in each case. These details shed a lot of light on the volume debate, and reveal that it may not be that contentious after all.

What data are available? (Part one)

Few studies have assessed the effects of training volume in strength-trained subjects (when comparing the number of sets to failure), although there are lots in untrained people. A recent meta-analysis included only 3 studies in strength-trained lifters (the first two on the list below, in addition to another one that did not measure muscle-specific changes in size). Since then, another 4 studies have been published, which gives 6 in total.

Before we begin, a couple of key points.

Firstly, we need to compare groups that trained with the same proximity to failure (and not just the same number of reps with the same percentage of 1RM), because the proximity to failure is what determines the mechanical tension that is experienced by each working muscle fiber, due to the force-velocity relationship. This equalizes the dose of training for each set between groups, at least when ignoring central nervous system (CNS) fatigue. Thus, we need to exclude two studies that have assessed the effects of training volume without controlling for proximity to failure, even though they were carried out in strength-trained lifters.

Secondly, we need to be aware that the researchers who conducted these studies did not always accurately identify the exercises that stimulate muscle growth in a body part. Consequently, their counts for the number of sets to failure for each muscle may need to be modified to calculate the correct number. After all, no student of biomechanics believes that the overhead press (which involves shoulder abduction)…