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 0.57, 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.