Perceived exertion scales attest to both intensity and exercise duration.

The present purpose was to study the relationships between perceived exertion (RPE, ETL) and exercise duration for all-out runs eliciting vVO2 max. 12 endurance-trained men performed three exhausting exercises on an indoor track. The first test was an incremental exercise to measure their maximal oxygen uptake (VO2 max), the velocity associated with VO2 max (vVO2 max), the velocity of the lacate concentration threshold (vLT) and the velocity delta 50 (vdelta50: the velocity halfway between vVO2 max and vLT). The second and third tests were a constant load all-out run at vVO2 max and vdelta50 to measure the time to exhaustion at these intensities (tlim vVO2 max and tlim vdelta50, respectively). vdelta50 corresponded to 90.1 +/- 2.5% vVO2 max; tlim vVO2 max and tlim vdelta50 were equal to 286 +/- 71 sec. and 547+/- 157 sec., respectively. For a same given relative time (%tlim), athletes perceived exercise as harder and felt that they could endure less for vVO2 max than vdelta50. When subjects began to perceive exercise as "hard" (RPE = 15), they had run for only 36.4 +/- 26.8%tlim at vVO2 max, whereas they had run for 46.1 +/- 15.7 %tlim at vdelta50. These results indicate that RPE and ETL scales were a combined subjective estimation of both intensity and exercise duration for all-out runs at 90 and 100% vVO2 max. Therefore, this scale could be used to assess duration as well as intensity of exercise for the practical application in sport. Moreover, it could be suggested that exercise duration can be prescribed as a function of perceived exertion for healthy normal people. Consequently, perceived exertion could be an important tool to individualize the prescription of a training program.