Growth status and estimated growth rate of young distance runners.

A mixed-longitudinal design was used to evaluate the growth status (size attained) and estimated growth rate of competitive young distance runners. Twenty-seven male and 27 female distance runners were enrolled in the study based on race performance times. Ages ranged from 8.0 to 15.1 years at initial visit. Twenty males and 16 females were followed at approximate annual intervals for 4 or 5 years. Stature (cm) and body mass (kg) were measured on each occasion and annual growth velocities were estimated. Stature and body mass were plotted relative to age- and sex-specific U.S. reference data, while estimated velocities of stature (cm/yr) and body mass (kg/yr) were plotted relative to age- and sex-specific percentiles from the Zurich Longitudinal Study. Differences in growth pattern between the runners and the reference values were compared statistically with a growth curve estimation regression model. Mean statures of male and female distance runners approximate the reference medians, while mean body masses are slightly below reference medians. Mean stature and body mass also maintain a constant position relative to the reference values in both sexes over time. Estimated velocities for stature and body mass are, on average, similar to age- and sex-specific medians for Swiss youth. Slope values indicate no significant difference in growth patterns between young distance runners and reference values. The findings are consistent with other data indicating that intensive endurance training during childhood and adolescence does not influence size attained and rate of growth in stature and body mass.