OBJECTIVE To test the validity of the Cart and Load Effort Rating (CALER) and OMNI bike RPE scales. METHODS Children (16 boys aged 9.5 +/- 0.7 and 16 girls aged 9.4 +/- 0.8) performed a progressive exercise test on a cycle ergometer to exhaustion. Random effects models and correlation analysis were used to determine the association of the undifferentiated perceived exertion from the CALER and OMNI bike scales with heart rate and V O2 for concurrent validity and the association of the CALER scale with the validated OMNI bike scale for construct validity. Tests of proportions were performed to compare the proportion of maximal RPE scale (CALER, OMNI bike) with the proportion of maximal heart rate achieved during the final stage of the exercise test. RESULTS Concurrent validity of the CALER and OMNI bike scales was established, as increases in scores of both scales were associated with (P < or = 0.001 regression) increases in heart rate (r = 0.88 and 0.89) and V O2 (r = 0.92 and 0.93). Construct validity of the CALER scale was established through a significant (P < or = 0.001 regression) relationship with the OMNI bike scale (r = 0.93). The proportion of maximal CALER (75 +/- 20%) and OMNI bike (74 +/- 19%) scales were less (P < or = 0.001) than the peak percentage of the predicted maximal heart rate (94.5 +/- 3%). CONCLUSIONS Validity for both the CALER and OMNI bike RPE scales was established for a progressively increasing exercise paradigm. However, the proportion of maximal perceived exertion scores from both scales was lower than the proportion of predicted maximal heart rate achieved during the final stage of the exercise test.