In recent years, a self-selected exercise intensity (SSEI) method and its protocol consisting of 5-min fixed-load cycling at 70% of maximal oxygen uptake followed by 15-min SSEI cycling (SSFL_70%) has been accepted as an intensity regulation method for better exercise prescription. The method simplifies exercise prescription and contributes to exercise habituation. There were no significant differences in ratings of perceived exertion (RPE) during exercise between the SSEI method and SSFL_70%. However, the percentage of maximal load (%load_max) regulated by each method differed significantly. These results suggest that the regulated intensity is not based on RPE in either or both of the two methods. In the present study, the interrelation between RPE and the values of physiological variables, and between RPE and the exercise load during the SSEI method and SSFL_70% was examined chronologically. Thirty-six healthy men (aged 25.3±2.7 years, mean±SD) performed two trials consisting of 20-min cycling exercise using both the SSEI method and SSFL_70% protocols. The coefficient of cross-correlation between FECO₂ and RPE for cardiorespiratory function calculated during exercise was higher for the SSEI method than for SSFL_70%. The tendency for the higher cross-correlation in the SSEI method was ascertained from the RPE value for the femoral region and %load_max. However, the time cycle of positive to negative changes in the coefficients of cross-correlation was relatively shorter for SSFL_70% than for the SSEI method. These results suggest that changes in physical condition and workload during exercise using SSFL_70% are reflected in RPE in the short term compared with the SSEI method.