There’s always a lot of chatter about the effects of training volume on muscle growth, but the impact of training volume on strength gains is often overlooked. A 2017 meta-analysis by Ralston and colleagues analyzed the extant literature, comparing the effects of low (5 or fewer working sets per exercise per week) versus moderate-to-high (6-10+ sets per week) training volumes on strength gains.
They found that higher volumes led to larger strength gains, but the effect was pretty small (effect size of 0.18). In practical terms, it means that doing, say, 10 hard sets of squats per week instead of 5 may increase your rate of strength gains by 20-25%. To the researchers’ credit, they also did several sub-analyses and robustness checks (looking at the effects on just multi-joint exercises or just single joint exercises, etc.), and found that the effect estimate stayed within a fairly tight range (from 0.14-0.23), suggesting that, while the effect is small, it’s pretty reliable.
A logical question that follows is, “Why is the relative effect of volume on muscle growth so much larger than the effect on strength?” I think the answer is pretty straightforward. While higher training volumes tend to produce more muscle growth, plenty of other factors contribute to strength gains (namely, improved motor skills, especially with heavy loads). The studies in this meta-analysis were equated for intensity, which is a much larger drive of strength gains, at least over the short-to-moderate term.
As training status increases, I suspect that the importance of hypertrophy for continued strength gains increases (as your cushion to improve maximal strength via technique and skill improvements gets smaller), which would mean that the impact of training volume would get larger, but that’s just speculation on my part. That’s not what this meta-analysis was testing.
If you want to read more on the subject, we covered this meta-analysis in more depth in Volume 1, Issue 6 of MASS.