The purpose of this study was to quantify running economy (RE) during level treadmill running in 6-year-old children and to identify the potentially mediating effects of resting oxygen uptake and body fat percentage on sex differences in RE. Resting oxygen uptake (VO2), body fat, and RE at 5 mph were quantified in 15 boys and 20 girls following 30 min of treadmill accommodation. While absolute VO2 and mass-related values of gross and net VO2 were significantly higher in boys compared to girls, gross VO2 expressed relative to fat-free mass was not different between sexes. These results indicate that 6-year-old girls exhibit better RE compared to 6-year-old boys when VO2 is expressed as a function of total body mass. This sex difference in VO2 may reflect an increase in aerobic energy demands associated with the presence of a greater muscle mass in boys.
Don W. Morgan, Wayland Tseh, Jennifer L. Caputo, Ian S. Craig, Daniel J. Keefer and Philip E. Martin
Jason J. Rutkowski, Robert J. Robertson, Wayland D. Tseh, Jennifer L. Caputo, Daniel J. Keefer, Kristin M. Sutika and Donald W. Morgan
The purpose of this investigation was to determine whether either the differentiated ratings of perceived exertion (RPE) for the legs (RPE-L) or chest (RPE-C) were higher than the overall body RPE (RPE-O) in children performing treadmill walking. A differentiated RPE that was higher than the RPE-O was considered the dominant perceptual signal. Thirty-one 10-year-old participants (16 boys, 15 girls) performed six separate 5-min bouts of level treadmill walking at different speeds. During each bout of exercise, RPEs were recorded using the modified Children’s OMNI Scale. Oxygen consumption (VO2), heart rate (HR), and ventilation (VE) were measured during Minutes 4 and 5 at each walking speed. VO2, HR, and VE increased as walking speed increased, as did perceived exertion. No differences were observed among RPE-O, RPE-L, and RPE-C at any speed. In addition, boys and girls exhibited similar responses for each perceptual and physiological variable. In conclusion, a dominant differentiated perceptual rating was not found at slow-to-moderate treadmill walking speeds for either boys or girls. Neither the respiratory–metabolic nor peripheral ratings of perceived exertion appeared to dominate the whole-body sensory-integration process in this sample.