PRESCRIPTION OF EXERCISE INTENSITY FOR THE OBESE PATIENT - THE RELATIONSHIP BETWEEN HEART-RATE, VO2, AND PERCEIVED EXERTION

OBJECTIVE: It has been suggested that relative heart rate reserve (%HR R), relative oxygen uptake (%VO2peak), and rating of perceived exertio n (RPE) can be used interchangeably to prescribe exercise intensity. T he purpose of this study was to examine the relationship between %HRR, %VO2peak, and RPE in obese females prior to and following substantial weight loss. SUBJECTS: 122 obese females (%Body fat = 45.9 +/- 5.0%) who participated in a weight loss intervention program. METHOD: Functi onal aerobic capacity was measured at baseline and following 12 weeks of exercise training and weight loss using a multi-stage Modified Balk e treadmill protocol. The VO2, heart rate (HR), and RPE were measured at each stage, with VO2 and HR data converted to the percentages of th e peak levels attained. These multi-stage data were then analyzed usin g mixed-model regression procedures to examine the relationship betwee n %HRR, %VO2, and RPE. RESULTS: With RPE as the dependent variable, re sults indicated that %HRR and %VO2, corresponded to RPE values consist ent with existing guidelines (70% = 13-14 RPE), and this was true for analyses performed at baseline and following weight loss. Further, bas eline results indicated that %HRR and %VO2 corresponded to similar lev els of exercise intensity (40-70% HRR = 40-70% VO2peak). However, foll owing weight loss, %HRR represented a higher level of intensity than i ts corresponding %VO2peak. CONCLUSIONS: The results of this study sugg est that RPE can be used as subjective marker of exercise intensity in an obese female population. However, despite adhering to existing gui delines prior to weight loss, there may be a discrepancy in the relati onship between %HRR and VO2max following severe weight loss, possibly due to the decrease in resting HR following exercise training and weig ht loss. These findings directly impact the prescription and monitorin g of exercise intensity for obese patients.