Measurement study — 2016 — RPE & autoregulation
Novel Resistance Training-Specific Rating of Perceived Exertion Scale Measuring Repetitions in Reserve
What did the researchers investigate?
An RPE scale based on repetitions in reserve, in 29 experienced and novice squatters at several percentages of 1RM.
What did they find?
RPE was strongly and inversely related to bar speed in both groups. Experienced squatters were slower and rated higher RPE at their 1RM. The authors conclude the RIR-based RPE scale is a practical way to regulate daily training load.
What does this mean for training?
Rating a set by how many reps you could still have done is a practical, validated way to measure effort.
How does FitX AI use this evidence?
FitX AI uses the same scale: RPE 10 means no reps left, RPE 9 one left, RPE 8 two, RPE 7 three.
Where FitX AI's own choices go beyond this paper
Reps-left feedback. Reps-left is self-reported; accuracy varies between people, so one rating moves targets only a little.
RPE mesocycle. The 7, 8, 9, 10 ladder and the 5-week length are FitX AI design choices. The papers support training near failure and RPE/RIR as effort scales, not this exact schedule.
Limitations
29 participants, squat only, single testing session.