Training volume using time or distance. Simple tools like stopwatch on track or known course or GPS watch make this cinch. But volume is not very accurate way to measure the stress workout inflicted on your body.
Volume: It’s easy to track training volume using time or distance. Simple tools like on track or known course or GPS watch make this cinch. But volume is not very accurate way to measure the stress workout inflicted on your body. It just doesn’t tell you much, and it loses meaning when you begin comparing athletes of different fitness. Volume is too broad a measure.
Intensity: The research shows us that exercise intensity is the real key to fitness, but measuring the intensity of a workout accurately is much more difficult than measuring volume. The usual ways we measure intensity, such as a scale of perceived exertion, are subjective measures. Intensity is tough to measure objectively.
Heart rate: Heart rate bracelet doesn’t measure intensity directly; it just shows one biological effect of exercising. Heart rate is affected by factors unrelated to exercise like diet, temperature, caffeine, fatigue, medications, stress, electrolytes, and hydration. Heart rate is too variable and derivative.
Rating of Perceived Exertion: RPE asks you to assign a number to how hard you feel you are working, so by definition, your RPE can’t be wrong as a measurement of how your workout feels. But RPE is a subjective measure of how you feel, not an objective measure of how hard you are actually working.
There are many non-training variables that can affect how workout feels. Exercise physiologists and neuroscientists have made progress in identifying them. They include many of the variables that affect heart rate plus psychological and social variables like use to running with a partner, competing with a rival, the presence of a crowd of spectators, listening to music, etc.
In many ways, RPE is still a useful tool because how you feel really does matter! But are you more fit if a workout feels easier? Not necessarily. You just might be feeling better than usual that day. RPE isn’t a reliable way to judge the physiological demands of the workout. In the end, RPE is just too subjective.