Inter-modal comparisons of acute energy expenditure during perceptually based exercise in obese adults

Previous studies have suggested that if exercise intensity is established by perceived effort, the metabolic demand varies among exercise machines and the treadmill optimizes energy expenditure (EE). However, these studies have been completed utilizing young people with normal body fat percentages. Therefore, the purpose of this study was to assess whether there was a difference in acute EE when obese people used different exercise modes at a self-selected intensity (ratings of perceived exertion 11-12) commonly recommended for overweight individuals. Twelve obese subjects (7 male; 5 female; BMI>29 kg/m(2)), aged 37-71 y completed two familiarization trials on four machines: treadmill (TM), stationary cycle (C), body trec elliptical arm/leg (BT), and airdyne (AD). On separate days, subjects then completed a 15 min trial on each machine at a self-selected intensity corresponding to a target RPE of 11-12 on the Borg 15-point scale. Machine order was randomly assigned, and subjects were blinded to the workload throughout each trial. Workload was self-adjusted during the first 5 min and then remained stable for the rest of the trial. Physiological data were obtained during the last 5 min of each trial. The BT produced the highest rate of EE among exercise machines and C the lowest. These results suggest that perceptually-based exercise prescriptions are not reliable across modes typically found in a fitness center environment, and that weight-bearing arm/leg exercise optimizes EE during self-selected exercise of moderate intensity in obese subjects.