Role of obesity on cerebral hemodynamics and cardiorespiratory responses in healthy men during repetitive incremental lifting.

purposeThe goal of this study was to quantify obesity-related differences in systemic physiologic responses and cerebral hemodynamics during physical work to exhaustion.

methodsTwenty men, ten who are obese and ten of healthy weight, completed an incremental exercise lifting a box from 25 cm below to 25 cm above knuckle height at 10 lifts/min. The lifting started with a load of 5 kg and was increased by 2 kg every 2 min until participants reached either voluntary fatigue or two of the American College of Sports Medicine endpoints for maximum aerobic capacity. Cardiorespiratory and prefrontal hemodynamic responses were measured simultaneously during rest, incremental lifting, and recovery.

resultsThe non-obese group lifted for ~64 % longer than the obese group. Both groups reached similar peak pulmonary oxygen uptake at the termination of exercise; however, when these responses were expressed relative to their body mass, the obese group had ~60 % reduced oxygen uptake. As the load increased, steady increases in cerebral oxygenation and blood volume responses were observed in both groups up to ~90 % of the lifting trial. In contrast, at higher intensities (near 100 % of the lifting trial), cerebral oxygenation and blood volume decreased in the obese group, whereas it plateaued or slightly increased in the non-obese group, with greatest cerebral oxygen extraction occurring at the cessation of lifting trial.

conclusionThese findings suggest that acute exposure to repetitive lifting exercise decreases cardiorespiratory responses and cerebral hemodynamics in the group who are obese, which may contribute to their reduced lifting capacity.