What are we measuring? Considerations on subjective ratings of perceived exertion in obese patients for exercise prescription in cardiac rehabilitation programs

We sought to describe the differences in exercise prescription in obese subjects using attained METs as compared to the subjective perception of the effort using the Borg scale ratings of perceived exertion (Borg RPE). We studied 552 obese patients who underwent an exercise stress test in the setting of a rehabilitation program. Exercise was prescribed at 70% of peak attained METS. This method was compared to an exercise level prescription that induces a subjective perception of mild fatigue (13 on the 20 points Borg scale). Attained METS were 6.2 +/- 2.5 and Borg RPE was 15.2 +/- 1.7. Borg RPE was negatively related to intensity and duration of exercise. Females, patient with a lower level of education and patients on diuretics perceived higher efforts. Patients who stopped exercising because of dyspnea or angina reached a lower level of METs (4.7 +/- 1.7 vs 6.3 +/- 2.7 METs; P<0.001) but the perceived effort was similar (15.5 +/- 1.7 vs 15.2 +/- 1.7; P=0.252). The subjective method would have yielded a significantly higher training workload: 5.4 +/- 2.3 vs 4.3 +/- 1.8 (P<0.001). In conclusion, in obese patients, Borg RPE is not equivalent to attained METs in exercise prescription and it influenced by educational level. (C) 2008 Elsevier Ireland Ltd. All rights reserved.