Objective: It has been suggested that relative heart rate reserve (% HRR), relative oxygen uptake (% VO2peak), and rating of perceived exertion (RPE) can be used interchangeably to prescribe exercise intensity. The 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: Functional aerobic capacity was measured at baseline and following 12 weeks of exercise training and weight loss using a multi-stage Modified Balke treadmill protocol. The VO2, heart rate (HR), and RPE were measured at each stage, with VO2 and HR data converted to the percentages of the peak levels attained. These multi-stage data were then analyzed using mixed-model regression procedures to examine the relationship between % HRR, % VO2, and RPE.
Results: With RPE as the dependent variable, results indicated that % HRR and % VO2, corresponded to RPE values consistent with existing guidelines (70% = 13-14 RPE), and this was true for analyses performed at baseline and following weight loss. Further, baseline results indicated that % HRR and % VO2 corresponded to similar levels of exercise intensity (40-70% HRR = 40-70% VO2peak). However, following weight loss, % HRR represented a higher level of intensity than its corresponding % VO2peak.
Conclusions: The results of this study suggest that RPE can be used as subjective marker of exercise intensity in an obese female population. However, despite adhering to existing guidelines prior to weight loss, there may be a discrepancy in the relationship between % HRR and VO2max following severe weight loss, possibly due to the decrease in resting HR following exercise training and weight loss. These findings directly impact the prescription and monitoring of exercise intensity for obese patients.