Randomised trial — 2022 — Training volume · Hypertrophy · Strength
Progressive Resistance Training Volume: Effects on Muscle Thickness, Mass, and Strength Adaptations in Resistance-Trained Individuals
What did the researchers investigate?
12, 18 or 24 weekly lower-body sets over 8 weeks (two sessions a week) in 35 resistance-trained people who could squat about twice their body mass.
What did they find?
All groups gained strength. A strong trend suggested 18 sets improved the back-squat 1RM more than 24 sets. Muscle thickness and lean mass changed similarly in all groups: the number of weekly sets did not change muscle growth.
What does this mean for training?
For well-trained lifters, more sets beyond a moderate amount did not add muscle, and the highest volume was not best for strength.
How does FitX AI use this evidence?
FitX AI caps weekly targets at 20 sets per major muscle and does not keep adding sets to chase growth.
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.
Limitations
35 participants over 8 weeks, lower body only, in very strong trained lifters. The strength difference was a trend, not statistically significant.