Relationships between HR and VO2 in the obese

Purpose: To enable more targeted exercise prescription for the obese, the purpose of this study was to consider relationships between relative indices of V(overdot)O-2peak,V(overdot)O2R, HRpeak, and HRR in a sample of obese adults. In particular, the study aimed to determine whether %HRR was equivalent to %V(overdot)O-2peak or %V(overdot)O2R. A further aim was to evaluate whether the %V(overdot)O-2peak-%HRpeak relationship defined by the ACSM holds in the obese population, or whether there is a deviation in this relationship as is noted in individuals with low functional capacity. Finally, the study aimed to determine the degree of variability in relative workload relating to lactate threshold (LT). Methods: Thirty-two sedentary obese adults, 17 women and 15 men (42.1 +/- 9.6 yr; 37.4 +/- 5.7kg.m(-2)) attended a testing session each week for 3 wk. The three sessions involved 1) familiarization with testing protocols; 2) graded treadmill tests to evaluate submaximal and peak cardiorespiratory capacity; and 3) assessment of body composition via deuterium dilution, and resting HR (HRrest) and oxygen consumption (V(overdot)O-2rest) collected during assessment of resting metabolic rate (RMR) via a ventilated hood system. Results: The primary findings were that in the obese: 1) the %HRpeak-%V(overdot)O-2peak relationship was significantly greater than the ACSM recommendations, 2) the %HRR was equivalent with %V(overdot)O2R not %V(overdot)O-2peak, and 3) exercise prescription at fixed percentages of V(overdot)O-2peak or HRpeak corresponded with wide ranges of exercise intensities in relation to LT. Conclusions: The relationships between cardiorespiratory parameters defined in normal weight populations differ to some degree in the obese, and this has implications both for optimizing exercise intensity for weight loss and exercise adherence in obese adults.