RATINGS OF PERCEIVED EXERTION (RPE) DURING CYCLING EXERCISES AT CONSTANT POWER OUTPUT

The purpose of the present investigation was to study the overall rati ng of perceived exertion (RPEov) according to the 6-20 scale proposed by Borg (1970) and muscular RPE (RPEmv) in exercises at constant load. The relationship between RPE and heart rate for three different loads was studied during exhausting exercises in 10 participants. Whether t he drift of RPE during a 20 min exercise at constant load could be an index of the endurance time during longlasting exercises at constant l oad was also investigated. At 1-week intervals, the participants perfo rmed cycling exercises up to exhaustion at 60, 73, and 86% maximal aer obic power (MAP) measured during an incremental test. Heart rate, RPEo v, RPEmu and exhaustion time (t(lim)) were measured. The upward shift of the HRmax-RPE regressions was significant between 86, 73 and 60% MA P (p<0.001) for RPEov and RPEmu. This result suggests that the equatio n HR = 10 x RPE proposed by Borg (1973) for incremental exercise is no t valid for long-lasting exercise at constant load until exhaustion be cause the heart rate corresponding to a given RPE depends on load and time. Mean RPE increased linearly with time up to exhaustion. Unexpect edly, the relationships between RPEmu or RPEov and percentage of exhau stion time were similar for exercises at 60 and 73% MAP although the e xhaustion times were very different (79.40+/-30.64 min versus 36.19 +/ - 15.99 min, respectively) (p<0.001). Consequently, it is likely that RPE was a subjective estimation of the hardness of exercise rather tha n the intensity of exercise. The RPE pattern at the beginning of long- lasting exercises at constant load (60 and 73% MAP) cannot be consider ed as a sensitive predictor of the point of self-imposed exhaustion fo r individuals. indeed, the errors in the estimation of exhaustion time from extrapolation of RPE at the beginning of exercise were very larg e. Moreover, at 60% MAP, a steady-state in RPE was observed during 20 min in five subjects whose t(lim) were not longer than t(lim) of the o ther subjects. In addition, the data of the present study indicate tha t RPEmu could be more useful than RPEov in cycling.