The energy cost of horizontal walking and running in adolescents

Purpose: This study developed and cross-validated generalized equations for predicting VO2 (mL.kg(-1).min(-1))and caloric expenditure (kcal.kg(-1).min (-1)) during horizontal walking and running in adolescents. Methods: Subjec ts were 47 male and 35 female adolescent volunteers, ages 12-18. Each subje ct underwent a submaximal treadmill exercise test to determine VO2 at rando mly selected walking and jogging speeds (67-215 m.min(-1)). Caloric expendi ture was estimated from VO2 and RER. Multiple regression was used to develo p prediction equations for estimating VO2 and caloric expenditure from a de rivation sample of 77 random observations, both walking and running. Result s: The group relationship between running speed and energy cost in the deri vation sample was linear, whereas the relationship between walking speed an d energy cost was quadratic. Gender, age, and height each failed to account for significant additional variation in energy cost after speed and mode w ere considered. Skinfolds accounted for a small yet significant amount of a dditional variation in energy cost. The derived equations were cross-valida ted on a sample of 76 separate random observations. The cross-validation st atistics are: for VO2, R = 0.95, error = 3.58 mL.kg(-1).min(-1), and for ca loric expenditure, R =0.94, error = 0.019 kcal.kg(-1).min(-1). Most selecte d adult equations consistently underestimated both VO2 and caloric expendit ure in the cross-validation sample. Conclusions: These results suggest that in adolescents, within the range of speeds tested, the relationship betwee n speed of movement and energy cost for running is linear, but for walking is curvilinear. Also, adult models for estimating VO2 or caloric expenditur e do not account for the higher relative energy cost of walking and running in adolescents.