Meta-analysis — 2025 — Training volume · Training frequency · Hypertrophy · Strength
The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains
What did the researchers investigate?
The dose-response of weekly set volume and training frequency for muscle growth and strength, using meta-regressions of 67 studies with 2,058 participants. Sets were classed as direct or indirect for the muscle measured.
What did they find?
Counting indirect sets as half a set (the 'fractional' method) fitted the data best. Muscle size and strength both increased as weekly volume increased, with diminishing returns, more pronounced for strength. Higher frequency was compatible with a negligible effect on muscle size, but strength gains increased with frequency, again with diminishing returns.
What does this mean for training?
More weekly sets help, but each extra set adds less. Sets for helping muscles (like triceps in a bench press) count, but less than direct sets. How often you train a muscle matters less for size than total sets do.
How does FitX AI use this evidence?
FitX AI counts a set as one set for the main muscle and half a set for helping muscles, sets weekly targets by experience instead of 'more is always better', and lets you train each muscle once or twice a week.
Where FitX AI's own choices go beyond this paper
Weekly sets per muscle. The bands (8-12, 12-16 or 16-20 sets) and the half-set counting are FitX AI choices; the research gives trends, not individual prescriptions.
Once or twice a week. Twice a week is a default that spreads the sets, not a requirement.
Limitations
Most participants were young men (79% male, average age about 25). Meta-regression across studies shows associations and cannot prove what will happen for one person.