Purpose: This study aimed to explore the influence of differences in relative skeletal maturity on performance test outcomes in elite youth soccer players from the Middle East.
Methods: We integrated skeletal age and performance assessments using mixed-longitudinal data available for 199 outfield players (chronological age range, 11.7 to 17.8 yr) enrolled as academy student-athletes (annual screening range, 1 to 5 visits). Skeletal age was determined as per the Tanner-Whitehouse II protocol. Relative maturity was calculated as the difference (∆) between Tanner-Whitehouse II skeletal age minus chronological age. Performance test outcomes of interest were 10-m sprinting, 40-m sprinting, countermovement jump height, and maximal aerobic speed. Separate random-effects generalized additive models quantified differences in performance test outcomes by relative skeletal maturity. Estimated differences were deemed practically relevant based on the location of the confidence interval (95% CI) against minimal detectable change values for each performance test outcome.
Results: For 40-m sprinting, differences of +0.51 s (95% CI, +0.35 to +0.67 s) and +0.62 s (95% CI, +0.45 to +0.78 s) were practically relevant for relative maturity status of ∆ = -1.5 yr versus ∆ = +0.5 and ∆ = +1 yr, respectively. For countermovement jump height, a difference of -8 cm (95% CI, -10 to -5 cm) was practically relevant for ∆ = -1.5 yr versus ∆ = +1 yr relative maturity status comparison. Effects for 10-m sprinting and maximal aerobic speed were unclear.
Conclusions: Integration of skeletal age and performance assessments indicated that conventional maturity status classification criteria were inconsistent to inform player development processes in our sample. Between-player differences in test performance may depend on a substantial delay in skeletal maturation (∆ ≤ -1.5 yr) and the performance outcome measure.
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