Metabolic determinants of the age-related improvement in one-mile run/walk performance in youth.

We examined the metabolic determinants of the age-related improvement in 1-mile run/walk (MRW) performance in boys and girls. Treadmill VO2peak (ml.kg-1.min-1), running economy (VO2 in ml.kg-1.min-1 at 8 km.h-1; VO2econ), and %VO2peak used during a simulated MRW were determined in 92 boys and 53 girls, 7-17 yr of age. Simple linear regression analyses indicated that MRW time decreased 0.52 min.y-1, VO2econ decreased 1.0 ml.kg-1.min-1.y-1, %VO2peak increased 1.5%.y-1, and no significant change occurred in VO2peak. Multiple linear regression analyses indicated that the increase in %VO2peak used during the run accounted for about 42% of the decrease in MRW time with age. With the effects of VO2peak and %VO2peak held constant, the improvement in VO2econ accounted for an additional 31% of the age-related decrease in MRW time. We conclude that the age-related improvement in MRW performance in youth is explained primarily by an increase in the %VO2peak used during the MRW and improvement in VO2econ. Age-related changes in MRW time should not be used to infer changes in VO2peak.