Randomised trial — 2022 — Resistance training · Hypertrophy · Strength
Progressive overload without progressing load? The effects of load or repetition progression on muscular adaptations
What did the researchers investigate?
Progressing by adding load (same reps) versus adding reps (same load), in 43 trained men and women over 8 weeks.
What did they find?
Rectus femoris growth modestly favoured adding reps and strength slightly favoured adding load, but the differences were of questionable practical significance. Other outcomes were similar.
What does this mean for training?
Overload can come from more reps or more weight: both are valid.
How does FitX AI use this evidence?
FitX AI uses both: your reps rise within the 8-15 range first, then the weight goes up once you reach the top at the planned effort.
Where FitX AI's own choices go beyond this paper
Load progression. The 2% and 5% floors and the rep-ceiling rule are FitX AI choices inside the ACSM's 2-10% guidance.
8-15 working range. 8-15 is a practical default range, not a research-derived limit. 6-10 for barbell squats and hinges, and RPE 9 as their ceiling, are FitX AI choices to limit the fatigue of the most demanding lifts: no paper sets these numbers. A range the user has set is never changed.
Limitations
8 weeks, lower body only, 43 participants.