How much does training volume really influence muscle growth and strength? This within-participant study puts one leg to the test at a time.
Overview
- What did they test? The researchers examined whether higher weekly set volumes (16 vs. 8 sets per muscle group) lead to greater muscle hypertrophy and strength gains, using a replicated within-participant unilateral design to minimize genetic, nutritional, and lifestyle differences between conditions.
- What did they find? Higher volumes produced a small but detectable advantage for muscle growth on average, while strength gains were similar between high- and low-volume conditions.
- What does it mean for you? Most lifters can start with moderate weekly volumes and adjust based on progress rather than assuming more is always better. Higher volume may slightly boost hypertrophy for some, but for strength, quality and specificity of training matter more once a moderate threshold is met.
What’s the Problem?
Training volume is one of the most heavily discussed variables in resistance training, and is a key driver of muscle hypertrophy. A preprint meta-analysis that we previously covered 1 generally showed a dose–response relationship where higher weekly set volumes produce greater gains up to a point. Specifically, hypertrophy increased up to about 11 fractional sets per session, while strength improvements plateaued beyond just 2 direct sets per session.
A major limitation in much of this field is the reliance on parallel-group designs, where each participant completes only one volume condition. This approach yields group averages, which are then compared statistically, but masks the potentially large variability in how individuals respond to different training volumes.While many papers highlight gross variability in training outcomes, recent methodological critiques argue that this does not necessarily reflect true inter-individual response variation 2 3. Much of the observed spread in results can be explained by within-participant variation, such as measurement error or day-to-day differences, rather than meaningful changes in how people adapt to a training program.
This means that without the right study design, it is impossible to know whether higher or lower volumes genuinely work better for certain individuals, or whether the differences we see are mostly noise. Addressing this problem requires designs that can isolate true variability from confounding sources of variation. One of the best methods is to replicate different interventions within the same individuals, allowing for a direct comparison of responses that account for nutrition intake, sleep, and other lifestyle factors. This study uses exactly that approach, aiming to provide a clearer, more individualized picture of how training volume affects hypertrophy and strength.
Purpose
The purpose was to determine how different per-limb resistance training volumes affect muscle hypertrophy and strength when controlling for individual variability, using a replicated within-participant unilateral design. The goal was to assess whether higher volumes consistently lead to greater adaptations or if responses vary substantially between individuals.
Hypothesis
The researchers hypothesized that higher training volumes would produce greater increases in muscle size and strength compared to lower volumes, but there would be no clear evidence of inter-individual responsiveness.
