Measurement of Peak Oxygen Consumption

Peak oxygen consumption (VO_2peak) was measured by indirect calorimetry (Quark, Cosmed USA, Chicago, IL) during a graded treadmill exercise test on a motorized treadmill. Subjects walked at a constant velocity with the grade initially set to 0% and increasing 4% after the first 2 minutes and 2% every 2 min thereafter to volitional exhaustion, as reported previously (Ivey et al., 2007 (link); Prior et al., 2009 (link)). Tests were terminated at the subject’s request or according to criteria set forth by American College of Sports Medicine (Pescatello et al., 2014 ). Subjects were allowed handrail support but were instructed to minimize handrail use to that necessary to maintain balance. VO_2peak was defined as the highest oxygen consumption value obtained in the last minute of exercise.