0842 Evidence supports the use of ratings of perceived exertion (RPE) 15-grade scale, as a valid marker of physiological exercise intensity, in a variety of sex, age, health status and ethnicity settings. Few references on the use of the scale for assessing young, non-Caucasian, sedentary populations are available. Cultural and psychophysical issues may impair the correlation between the scale and the maximal heart rate (MHR). PURPOSE: To evaluate the impact of aerobic training on the concordance of RPE and MHR after maximal and submaximal efforts in young, sedentary, Hispanic adults. METHODS: 61 (15 men, 46 women) young (19.63 ± 0.81 yrs), Hispanic, volunteer, 3rd year medical students were enrolled. Standardized instructions for use of the RPE rd scale were given before testing. Subjects initially performed the 6-min walk test (6MWT). Reached distance (D), RPE and MHR (Polar Electro Oy), were recorded at the end of the test. On a different day, the 20m-Shuttle run test (20MST) was delivered. Predicted V02max, RPE and MHR were recorded at the moment of volitional exhaustion. After a standardized 10-week training program, subjects underwent both maximal (20MST) and submaximal (6MWT) tests. The training program consisted of two 60-min sessions weekly, with workloads between 30 to 50% of V02max reserve. Two-tailed Pearson coefficients were performed to determine the correlation between RPE scale and MHR for both tests. T-paired test was used to determine differences after the intervention for all measured variables. RESULTS: After the aerobic training program, predicted VO2max (30.84 ± 6.06 ml·kg−1·min−1 vs 33.01 ± 6.32 ml·kg−1·min−1; p<0.01) and 6MWT D (714.34 ± 63.53 m vs 750.54 ± 86.69 m; p<0.05) improved significantly. Significant differences were found for MHR reached after training for the maximal test (191.8 ± 9.42 beats·min−1 vs 189.04 ± 12.53 beats·min−1; p = 0.040) but not for the submaximal test (180.09 ± 13.72 beats·min−1 vs 180.92 ± 12.87 beats·min−1; p = 0.80). RPE recorded at the end of the 20MST and 6MWT was respectively (15.63 ± 1.73 and 11.88 ± 1.83) before and (16.36 ± 1.96 and 14.09 ± 1.84; p<0.05) after the training program. Increases in the correlation levels between RPE scale and MHR were found for the 20MST (from r = 0.21 p = 0.099 to r = 0.40 p = 0.004) and the 6MWT (from r = −0.03 p = 0.807 to r = 0.32 p = 0.015). CONCLUSION: The accuracy of the RPE 15-point scale for the initial assessment of relative exercise intensity, at maximal and submaximal efforts, was poor in our study group. The 10-week aerobic training improved significantly the validity of the scale. Psychophysical experience of exercise intensity, enabled by an aerobic training program, may improve the RPE.