Meta-Analysis Reveals Key Insights on Training Volume and Frequency

The dosage of strength training is a cornerstone in exercise prescription aimed at increasing muscle mass and developing maximum strength. Among the elements that shape this dosage, two variables have gained particular relevance: weekly volume, measured in the number of sets, and the frequency of training per muscle group or specific movement. Despite the growing literature on strength training, the exact nature of the dose-response adaptation remains uncertain, especially at high workloads.

Previous meta-analyses suggested positive relationships between volume and adaptations, but they had a clear limitation: they categorized data arbitrarily (e.g., ≤5 vs. >5 sets per week) instead of treating volume as a continuous variable. Additionally, frequency was often analyzed in isolation, generally concluding that it does not exert an independent effect on hypertrophy when volume is matched among groups, though results for strength have been contradictory.

The current study aims to fill these gaps through continuous meta-regressions that model both linear and non-linear relationships, incorporating a novel approach to quantify volume: differentiating direct and indirect sets, assigning a weighted value to the latter when they involve muscles not primarily responsible for the evaluated movement.

The study pursues four main objectives, including evaluating which method of quantifying volume (total, direct, or fractional) best predicts adaptive outcomes. A systematic review and meta-analysis were developed with multi-level meta-regressions, including 67 studies with 2058 participants, predominantly young adults (average age 25 years). The average duration of the programs was approximately 10 weeks, with inclusion criteria demanding rigorous standards.

The fractional method assigned a value of 0.5 to each indirect set, justified by prior evidence indicating that non-primary agonist muscles receive less stimulation. The predictive models were also adjusted for various factors.

The models demonstrated a 100% probability that higher weekly volumes are associated with greater increases in muscle mass. However, this relationship is not linear: a pattern of diminishing returns was observed, where initial increases in volume yield substantial hypertrophy, but the marginal benefit per set progressively decreases.

Understanding Volume's Impact on Strength Gains

Modeling volume as a continuous variable, it was found that the minimum volume capable of exceeding the detectable effect is around 4-5 sets per week, while higher ranges (>20 sets per week) show gains that increase less significantly and with wider uncertainty intervals. The relationship was also positive for strength, but a more pronounced plateau effect was noted. The model showed that strength gains scale with volume, but a functional plateau appears more quickly than hypertrophy, beyond which adding more volume does not yield clear improvements.

The models did not show a clear and consistent relationship between weekly frequency and hypertrophy when adjusted for total volume. The slope is compatible with a neutral effect, likely small. A potential modulatory effect in certain contexts (e.g., high training level, recovery capacity, load progression) cannot be ruled out, but overall, there is no robust signal.

In contrast to hypertrophy, frequency did show a positive relationship with strength. Each additional increase in frequency (1→2, 2→3) translates to greater improvements, albeit with diminishing returns as frequency increases. This appears to be linked more to neuromuscular factors than structural ones: more opportunities to practice the evaluated movement lead to greater neural efficiency, better technical control, and potentially heavier loads managed in subsequent training sessions.

The authors interpret that hypertrophy depends on sustained cumulative and mechanical stimuli derived from repeated metabolic and tension stress over time. Direct sets better reflect that stimulus, and therefore the fractional method improves the predictive model. The identified plateau seems consistent with the saturation of muscle anabolic pathways and homeostatic mechanisms.

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Typical volume levels in studies (~10-13 sets per week) likely mean redistributing sets across 1, 2, or 3 sessions does not significantly affect hypertrophic response. The authors propose hypotheses regarding this phenomenon.

The most novel finding is not only statistical. Practically, it implies a relevant technical line for advanced planning. Access to the original article is available at: https://www.fisiologiadelejercicio.com/wp-content/uploads/2025/12/The-Resistance-Training-Dose-Response.pdf. Pelland JC, Remmert JF, Robinson ZP, Hinson SR, Zourdos MC. The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains. Sports Med. 2025 Dec 4. doi: 10.1007/s40279-025-02344-w.