The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of intervention trials
PubMed 41343037 · doi:10.1007/s40279-025-02344-w
What was done
A multi-level meta-regression of 67 studies including 2,058 participants (79.1% male, 20.9% female; mean age 25.16 ± 5.22 years) evaluated the dose-response relationship of weekly resistance training set volume and frequency with muscle hypertrophy and strength gains. Sets were categorized as direct or indirect based on measurement specificity and quantified as total (indirect = 1), fractional (indirect = 0.5), or direct (indirect = 0). Models were adjusted for training status and intervention duration.
What was found
The fractional quantification method (indirect sets = 0.5) provided the strongest relative model evidence. For weekly volume, the posterior probability of the marginal slope exceeding zero was 100% for both hypertrophy and strength, indicating greater adaptations with higher volume, accompanied by diminishing returns that were more pronounced for strength. For weekly frequency, the posterior probability of the marginal slope exceeding zero was <100% for hypertrophy (consistent with negligible effects) and 100% for strength (indicating gains with diminishing returns).
Why it matters
This study clarifies that weekly set volume drives both hypertrophy and strength with diminishing returns, whereas training frequency primarily enhances strength. It also demonstrates that fractionally weighting indirect exercises provides more accurate dose-response modeling for resistance training prescription.
Limits
The study sample was heavily skewed toward young adult males (79.1% male, mean age ~25 years), limiting generalizability to females and older populations. Specific numerical effect sizes, parameter estimates, and exact plateau thresholds are not detailed in the abstract.