Fitness, body size, ventilation and the oxygen cost of breathing in adults

The purpose of the study was to characterize the oxygen cost of ventilation (VO2VENT) response at submaximal and maximal efforts in men and women with different fitness levels, body sizes, and ages and to determine which factors contribute significantly and independently to maximal VO 2VENT. Twenty healthy, non-smoking men (n=18) and women (n=2) participated in the study. During the first visit to the laboratory, height and body mass were measured and body surface area and body mass index were calculated using standard procedures. Fitness (VO2max) and submaximal and maximal ventilation rates were then assessed by an incremental cycle ergometer test. During the second visit, subjects mimicked submaximal and maximal ventilation rates in a cycling posture. Curve fitting (regression) was used to characterize the VO2VENT response to incremental exercise. Multiple regression was used to determine if subject characteristics (body surface area, body mass, body mass index, VO2max, maximal ventilatory equivalent, or maximal ventilation) were independently related to maximal VO2VENT. Body surface area, body mass, body mass index, VO 2max, and maximal ventilation were significantly and independently related to maximal VO2VENT (P < 0.001). Body surface area, body mass, and maximal ventilation were the strongest contributors to maximal VO 2VENT. Although approximately 60-70% of the variance in maximal VO2VENT could be explained, the remaining large unexplained between subjects variability in maximal VO2VENT warrants further research in this area