Ratings of perceived exertion (RPE) as an index of aerobic endurance during local and general exercises

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Abstract
The main purpose of this study was to assess the correlations of RPE with indicators of endurance (critical power), exhaustion time and the electromyographic activity of a relevant muscle during general and local exercises. Eight healthy subjects participated in the study. During the first session, Maximal Aerobic Power (MAP) was measured by means of an incremental cycling exercise on a Monark ergometer. At 1-week intervals the participants performed a general or local exhausting exercise, which consisted of a cycle exercise (60, 73, 86 or 100% MAP) and a knee extension exercise (lifting a load between 17.5 and 32.5 kg every 3 s), respectively. The critical powers corresponding to cycling (CPcycling) and knee extension (CPknee) were calculated from the slope of the linear relationship between exhaustion time (t lim) and work. Rate of perceived exertion, concerning the whole body (overall RPE [RPEov]), RPE concerning the exercising muscles (muscular RPE [RPEmu]) and exhaustion time were measured. During the last session, the integrated electromyogram of the right Vastus Lateralis (iEMG s−1) was measured during short (20 s) cycling and knee extension nonexhausting exercises, with the same electrode location, at the different power outputs used during the exhausting exercises. The relationships between RPEmu at the fifth minute and log t lim and between iEMG% (percentage of the iEMG s−1 corresponding to 100% MAP during cycling) and log t lim were similar for the cycling and knee extension exercises. The mean values of RPEmu at the fifth minute of exercise calculated for CPcycling and CPknee were almost equal (12.3 ± 1.7 versus 12.2 ± 0.9). Similarly, the mean values of iEMG% corresponding to CPcycling and CPknee were equal (78.44 versus 79.02%). These results suggest that RPEmu is related to aerobic endurance and that the possibility of sustaining a high percentage of maximal aerobic power during a general exercise is mainly related to local muscular factors.