GROWTH FACTORS SIGNIFICANTLY INFLUENCE AGE-GROUP PERFORMANCE
Toussaint, H. M., de Looze, M., van Rossem, B., Leijdekkers, M., & Dignum, H. (1990). The effect of growth on drag in young swimmers. The Journal of Sport Biomechanics, 6, 18-28.
Children (M = 4; F = 9; average age 12.9 yr) were studied before and after a period of 2.5 years by assessing anthropometric variables, active drag, and performance levels.
All anthropometric variables save one, increased significantly. Height changed from 1.52 to 1.69 m and weight from 40.0 to 54.7 kg. Axillary cross sectional body area (the single most influential variable related to drag in adults) increased by 16%, however, there was no change in the drag coefficient in these subjects over the duration of the study.
The explanation for the stable drag coefficient was that there was a decrease in wave-making resistance and an improvement in the streamline form of the athletes. Those two factors offset the extra friction caused by increased body surface and frontal resistance.
Performance improved over 100 m by 14% which was related to significant increases in maximum force (34%), velocity (12%), and power (49%).
Implication. Growth factors strongly influence performance of age-group swimmers over 100 m. Thus, advanced maturers will have a distinct advantage over late maturers between the ages of 13 and 15 years. Swimmers remain consistent in their active drag quantities although their shapes change markedly throughout this growth period.
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