Calibrate the Borg scale to your actual physiology
The 6–20 Borg scale (or 0–10 RPE) only works if you know what each number feels like in your own body.
Why it works
The original Borg scale runs 6–20, designed so the number multiplied by 10 approximates heart rate for a typical adult. The modified CR10 (0–10) scale is more intuitive. Both work because perceived exertion integrates respiratory, cardiovascular, muscular, and central signals into a single number that correlates strongly with lactate and ventilatory thresholds. The scale is only as useful as your ability to anchor the numbers to real physical states.
How to do it
- During a cardio session, note your effort at several intensity levels alongside HR if available.
- Anchor the extremes: 10 (Borg: 20) is maximal, can’t sustain beyond 15–30 seconds; 4–5 (Borg: 13–15) is comfortably hard.
- Do this anchoring over 2–3 sessions until the numbers feel stable and consistent.
- Use the CR10 scale (0–10) for simplicity; use the 6–20 scale if working with coaches who use it.
Evidence
The Borg RPE scale correlates strongly with heart rate, VO2, and blood lactate across populations — one of the most validated tools in exercise science. (rct)
Perceived exertion can be distorted by mood, motivation, training status, and environmental conditions; it is most accurate as a longitudinal comparative tool within an individual.
Sources
- Borg (1982), psychophysical bases of perceived exertion, Medicine & Science in Sports & Exercise
Common mistake
Anchoring RPE to how hard you "should" be working rather than to actual physical sensations — which leads to systematically underestimating effort on easy days and overestimating on hard ones.
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More practices for The RPE Scale
- Autoregulate daily training load using RPE
If a planned moderate session feels like an 8/10 instead of the usual 6/10, your body is telling you something — adjust the session accordingly.
- Use RPE to set strength training load instead of fixed percentages
An RPE 8 on a squat means two reps left in the tank — this calibrates load to your actual state on that day.
- Use post-session RPE review to detect overreaching early
Track the RPE drift across a training block — rising RPE at the same load is the earliest signal of overreaching.
- Use RPE to set cardio intensity without heart rate monitors
Target RPE 5–6 for aerobic base, 7–8 for tempo, 9–10 for intervals — all without needing a heart rate monitor.
- Use RPE as a communication language with coaches and training partners
A shared RPE vocabulary turns subjective experience into objective programming data that a coach can act on.
Related concepts
- Zone 2 Training
Mitochondria, metabolic flexibility, and the aerobic base that underlies everything else
- Supercompensation
How stress, recovery, and adaptation interact — and how to time them to peak on demand
- Progressive Overload
The fundamental principle of physical adaptation — and how to apply it without breaking down
- Deload Week
How planned recovery phases convert training stress into realized gains