Waldron, MarkWorsfold, Paul R.Twist, CraigLamb, Kevin L.2014-09-192014-09-192014-11-30Waldron, M., Worsfold, P., Twist, C., & Lamb, K. (2014). Changes in anthropometry and performance, and their interrelationships, across three seasons in elite youth rugby league players. The Journal of Strength & Conditioning Research, 28(11), 3128-3136.1064-801110.1519/JSC.0000000000000445http://hdl.handle.net/10034/326266This is a non-final version of an article published in final form in Journal of Strength and Conditioning Research, 2014, 28(11), pp. 3128-3136.This study investigated changes in anthropometry and performance, and their inter-relationships, across three consecutive seasons (under-15 to under-17 age group) in elite youth rugby league players. Each player took part in annual anthropometrical and performance assessments, comprising measurements of stature; body mass; limb lengths and circumference; skinfolds, predicted muscle cross-sectional area (CSA); 20 m speed, counter-movement jump height, vertical power and aerobic power. Lean body mass % changed (P < 0.05) between the under-15 (70.9 ± 5.9 %), under-16 (72.0 ± 5.8 %) and the under-17 age groups (74.1 ± 5.7 %). Likewise, predicted quadriceps muscle cross-sectional area (CSA) also changed (P < 0.05) between each age group (under-15 = 120.9 ± 37.8 cm2; under-16 = 133.2 ± 36.0 cm2; under-17 = 154.8 ± 28.3 cm2). Concomitant changes between the under-15 and under-16 group were found for 20 m speed (3.5 ± 0.1 cf. 3.4 ± 0.2 s; P = 0.008) and predicted jumping power (3611.3 ± 327.3 W cf. 4081.5 ± 453.9 W; P = 0.003). Both lean body mass and quadriceps muscle CSA consistently, related to both 20 m sprint time and jumping power, with r-values ranging between -0.39 to –0.63 (20 m sprint time) and 0.55 to 0.75 (jumping power). Our findings demonstrate the importance of gains in lean body mass across later-adolescence that support the ability to generate horizontal speed and predicted vertical power. This information should inform the expectations and subsequent training programs of elite rugby league practitioners.enteam sportspeedpowerArticle1533-4287Journal of Strength and Conditioning Research