The purpose of the present investigation was to determine to what extent the protocol (incremental and constant load exercises) affects the ratings of perceived exertion for a given submaximal intensity on a cycle ergometer. 10 healthy and well-trained male students (M age=23 yr., SD=2.9) performed an incremental exercise to determine maximal oxygen uptake (VO2 max), maximal aerobic power, and the ratings of perceived exertion (CR10) corresponding to 70% and 75% VO2 max (CR10(70i) and CR10(75i)). Two 30-min. constant load exercises set at these intensities were performed to establish the corresponding CR10 values. CR10(70i) (5.6 +/- 1.9) and CR10(75i) (6.2 +/- 1.9) were significantly higher than all CR10 values collected at Minutes 5, 10, 15, 20, 25, and 30 of the constant load exercises. These results indicate that, for a given exercise intensity (70% and 75% VO2 max), subjects are rated higher during an incremental exercise than during a 30-min. submaximal constant load test. Therefore, when coaches and physiotherapists want to use CR10 values reported during an incremental standard exercise to set training loads, they have to be prudent since the same relative exercise intensity does not seem to be perceived identically during a submaximal constant exercise as during an incremental one.