Analysis of the Relative Age Effect in Elite Youth Judo Athletes.

The purpose of this investigation was to evaluate relative age effects (RAEs) in elite youth judo athletes from different chronological age groups, between sexes, and across weight categories. Data from 1542 place winners of the cadet (under 17 y, 2009-2013) and junior judo world championships (under 20/21 y, 1990-2013) were separated by birth month into quarters (Q1, Q2, Q3, and Q4). The observed values were compared with expected annual age distributions using χ2 analyses, and odd ratios (OR) were used to evaluate effect sizes between quarters. The observed frequency of place winners was significantly different from the expected frequency for the age-group and sex comparisons and all body-mass groups (P < .05) with the exception of the extra-light categories (P = .572). When comparing Q1 with Q4 (OR, 95% confidence interval), small effect sizes were observed for cadets (1.72, 1.12-2.66), juniors (1.54, 1.23-1.94), males (1.75, 1.32-2.33), females (1.39, 1.03-1.87), and the light- (1.79, 1.21-2.64) and middle-weight (1.80, 1.20-2.70) categories. RAEs are apparent in cadet and junior judo athletes. Thus, coaches and administrators should consider the potential for physical and/or competitive advantages while adopting strategies that encourage long-term participation in youth judo athletes.