RPE (Rate of perceived exertion)

Rate of perceived exertion (RPE) is a subjective scale used to quantify how hard physical exercise feels, most commonly on the 6–20 Borg scale or the 0–10 modified scale. It correlates reasonably well with heart rate, lactate, and VO2 in trained individuals. RPE is widely used in longevity and endurance protocols to autoregulate training load, manage fatigue, and complement objective recovery metrics like HRV and resting heart rate.