Is There Too Much of a Good Thing?

This is the authors' abstract. We don't add key points for this paper.

Background: Recent research has quantified the dose-response relationship between weekly resistance training set volume and muscle hypertrophy and strength gains.However, the nature of the dose-response of per-session set volume remains underexplored.Objective: Before meta-analyzing, all contributing sets were classified as direct or indirect, depending on their specificity to the measurement.Then, per-session set volume for indirect sets was quantified as 1 for 'total,' 0.5 for 'fractional,' and 0 for 'direct.'A series of multi-level meta-regressions were performed for muscle hypertrophy and strength, with all models adjusted for intervention duration and training status.The point of undetectable outcome superiority (PUOS) was identified as the per-session set volume in which additional sets did not result in a >50% likelihood of the difference in hypertrophy or strength gain exceeding the smallest detectable effect size. Results:The 'direct' and 'fractional' quantification methods provided the strongest relative evidence for strength and hypertrophy, respectively; thus, these quantification methods were used for the primary meta-regression models.The posterior probability of the marginal slope exceeding zero for the effect of per-session volume on both strength and hypertrophy was 100%, indicating positive dose-response relationships between persession set volume and hypertrophy and strength gains.However, both best fit models suggest diminishing returns as per-session set volume increases, with the PUOS occurring at ~2 'direct' sets for strength and ~11 'fractional' sets for hypertrophy.Notably, the 'direct' set model for strength gains suggests more strongly diminishing returns compared to the 'fractional' set model for hypertrophy.Conclusions: There is a positive dose-response relationship between per-session volume with both strength and hypertrophy; however, to quantify the dose-response relationship, it is paramount to distinguish between 'fractional' and 'direct' set counting methods.Furthermore, the relationship exhibits diminishing returns for both outcomes, which appear to manifest more strongly for strength gains compared to hypertrophy.While the available evidence indicates a PUOS of ~2 and ~11 sets per session for strength gain and hypertrophy, respectively, there is insufficient data with very high per-session set volumes.Therefore, it is unclear whether there is a point in which additional per-session sets attenuate adaptations, or if even higher per-session set volumes could be potentially beneficial; thus, the PUOS should be interpreted cautiously.