In this study, running economy differences between boys and men at a common speed (ABS = 9.6 kph) and at a relative speed adjusted for body size (REL = 3.71 leg lengths per second) were examined. The caloric cost relative to mass was significantly higher for the boys for ABS (men = .17, boys = .20), but not for REL (both .19). The relative heart rate (%HRmax) and ventilatory equivalent were higher for the boys at ABS, but not at REL. Boys had significantly higher stride frequencies in both conditions. Stride length/leg length was greater for boys during ABS, and for men during REL. Respiratory exchange ratios (RERs) were not different at ABS (men = .94, boys = .96), but during REL, boys had a significantly lower RER (.93 vs. .98). Running economy differences between adults and children are reduced when speeds are adjusted relative to body size. This model may be useful for identifying developmentally based differences in the physiology and biomechanics associated with exercise.
Ann F. Maliszewski is with the Exercise Physiology Laboratory at SUNY Cortland, 232 Park Center, Cortland, NY 13045. Patty S. Freedson is with the Department of Exercise Science at University of Massachusetts, Boyden Gymnasium, Amherst, MA 01003.