The relative age effect is well documented with the maturation-selection hypothesis the most common explanation; however, conflicting evidence exists. We observed the birth-date distribution within an elite junior soccer academy. The influence of physical maturity status on anthropometric variables and sprinting ability was also investigated. Annual fitness testing was conducted over an eight-year period with a total of 306 players (age: 12.5 ± 1.7 y [range: 9.7 – 16.6 y]; stature: 156.9 ± 12.9 cm; mass: 46.5 ± 12.5 kg) drawn from six age categories (under-11s to -17s) who attended the same Scottish Premiership club academy. Measurements included mass, stature, maturity offset and 0-15 m sprint. Odds ratios revealed a clear bias towards recruitment of players born in quartile one compared to quartile four. The overall effect (all squads combined) of birth quartile was very likely small for maturity offset (0.85 years; 90% confidence interval 0.44 years to 1.26 years) and stature (6.2 cm; 90% confidence interval 2.8 cm to 9.6 cm), and likely small for mass (5.1 kg; 90% confidence interval 1.7 kg to 8.4 kg). The magnitude of the relationship between maturity offset and 15 m sprinting speed ranged from trivial for under-11s (r = 0.01; 90% confidence interval -0.14 to 0.16) to very likely large for under-15s (r = -0.62; -0.71 to -0.51). Making decisions about which players to retain and release should not be based on sprinting ability around the under-14 and under-15 age categories since any inter-individual differences may be confounded by transient inequalities in maturity offset.
McCunn, R., Weston, M., Hill, J. K. A. J., Johnston, R. D., & Gibson, N. V. (2016). Influence of physical maturity status on sprinting speed among youth soccer players. Journal of Strength and Conditioning Research, -. https://doi.org/10.1519/JSC.0000000000001654