Longitudinal stratification of gait economy in young boys and girls: the locomotion energy and growth study

The purpose of this study was to determine if the relative ordering of locomotor oxygen consumption (VO₂) values remains stable as healthy children age. Beginning at age 6 and ending at age 10, VO₂ during level treadmill walking and running was quantified in 15 boys and 18 girls who were tested on an annual basis. Following 30 min of treadmill accommodation to each exercise mode, subjects walked and ran for 5 min at 1.34 m s⁻¹ and 2.23 m s⁻¹, respectively. During the last 2 min of each 5-min stage, expired gas samples were collected and analyzed to quantify VO₂. For both walking (W) and running (R), 27% of subjects showed an average yearly change in VO₂ rank order of ≤2 positions, 64% (W) and 61% (R) displayed a mean annual shift in VO₂ rank order of ≤4 positions, and 85% exhibited a mean yearly fluctuation in W and R VO₂ rank order of ≤6 positions. Reliability analysis of VO₂ responses across the 5-year testing period also yielded high coefficient alpha values for walking (R=0.91) and running (R=0.94). These results suggest that the relative ordering of individual gait VO₂ values remains quite stable in young children, indicating a physiological stratification that is fairly resistant to change during a period featuring increases in physical growth and varied exposure to different types of physical activity.