Position stand — 2009 — Resistance training · Periodization · Strength
Progression Models in Resistance Training for Healthy Adults
What did the researchers investigate?
Recommendations for progressing resistance training for strength, muscle growth, power and endurance in healthy adults.
What did they find?
Among its recommendations: when you can perform the current load for one to two reps over the desired number, increase the load by 2-10%. For muscle growth it recommends loads of 1-12 RM used in a periodized way with emphasis on 6-12 RM, and higher-volume, multiple-set programs.
What does this mean for training?
Progress the weight in small steps once the target reps are clearly exceeded.
How does FitX AI use this evidence?
When you reach the top of your rep range at the planned effort, FitX AI adds at least 2% (5% for leg and hip lifts), inside the ACSM's 2-10% band.
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
An expert position stand from 2009; some areas (for example, light loads for muscle growth) have been studied much more since.