Fitness types are obsessed with numbers. If it’s not our bench press max or 5K time, it’s our body fat percentage or arm girth. We want hard evidence that we’re getting fitter, faster, stronger.
But there’s a fundamental flaw in the lab-rat approach to fitness. We may think we’re the Terminator in the gym, but we’re not cyborgs. We’re organic beings, and our bodies rarely respond to training predictably from one day, workout — or even set — to the next.
How to measure the output of such fickle creatures? One such means is the Borg Rate of Perceived Exertion Scale, or RPE.