In an earlier letter in Journal of Applied Physiology,1 I showed that in subjects exercising at a fixed work rate while either carbohydrate-replete or partially carbohydrate-depleted,2 the rating of perceived exertion (RPE) rises as a linear function of the duration of exercise that remains. At the time, I assumed that this was an entirely novel observation.

However, while searching the publication record of Dr Allen Cymerman, currently of the US Army Research Institute of Environmental Medicine, my attention was drawn to a paper coauthored by Dr Cymerman and published in 1979, entitled “Perception of effort during constant work to self-imposed exhaustion”.3

In that study, subjects walked or ran at 80% of maximum oxygen consumption (VO_2max) to “self-imposed exhaustion”. Exhaustion occurred at the same RPE during both prolonged submaximal exercise and during maximum exercise (for measurement of VO_2max). During prolonged submaximal exercise to exhaustion, RPE rose as a linear function of the percentage of total exercise duration3 (fig 1 of that paper, page 1117). In addition, the linear …