Studies found that cardiovascular responses to exercise are enhanced in individuals with obesity and are associated with a greater cardiac output (CO) response compared to normal weight controls. However, the mechanisms underlying these altered responses during dynamic exercise are not clear. We investigated whether the cardiovascular responses mediated by the muscle metaboreflex (MMR) activation are augmented in obese men during both static and dynamic exercise. Twenty males (10 obese (OG) and 10 non-obese (NOG)) were studied. Changes in CO, mean arterial pressure (MAP), and total vascular conductance (TVC) were compared between the two groups during dynamic handgrip exercise (DHE), post-exercise muscular ischemia (PEMI), and dynamic exercise corresponding to 40%, 60% and 80% workloads. Subjects completed 2 min of DHE at 30% of MVC, followed by 2 min of PEMI. MAP, CO, and TVC responses to DHE and dynamic exercise were significantly higher in OG, whereas there were no differences during PEMI. Increases in CO and MAP during mild to heavy dynamic exercise were seen in both groups, but the changes in these variables were greater in the OG. There were no significant differences in TVC between the two groups. Compared to NOG, the augmented blood pressure response to DHE and dynamic exercise in OG was associated with a greater increase in CO. Thus, the augmented CO and MAP responses were not associated with the activation of the MMR. Consequently, additional factors specific to obesity, such as the mechanoreflex, may have been involved.

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/m²), 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.