When it comes to strength training, two common ways to measure intensity are Reps in Reserve (RIR) and Rate of Perceived Exertion (RPE). Both tell you how hard you’re working, but they do it in different ways. Reps in Reserve (RIR): Counting What’s Left RIR is simple—you finish a set and estimate how many reps … Continue reading RIR vs. RPE: What’s the Difference?