Body composition and physical performance in under-17 and under-19 rugby players: differences and associations among forwards and backs

Abstract

This study aimed to compare body composition and physical performance between U-17 and U-19 rugby players (forwards and backs), and examine the correlations among body composition, relative strength, jump, and sprint performance in both playing positions. Fifty-two male adolescent rugby players (mean ± SD: age, U-17: 16.2 ± 0.6 and U-19: 18.09 ± 0.9 years) participated in the study. Players performed anthropometric, body-composition (∑3 skinfolds [SF], body fat [BF] and lean mass [LM]), vertical jump, 30-m sprint, and squat one-repetition maximum (1RM-SQ) tests. Significant differences were observed for body mass (BM) and body composition variables among playing positions for both categories (P: 0.05 to < 0.001; ES > 0.72). U-17 forwards showed significantly different performance across all variables when compared to U-19 backs (P: 0.05 to < 0.001; ES > 1.08). Likewise, U-17 forwards showed lower relative strength (P: 0.05–0.095; ES > 1.66) and higher 30-m sprint times (P < 0.024; ES > 0.57) when compared to U-19 forwards and U-17 backs. Overall, for the backs, BM and LM were significantly associated with all performance variables (r: −0.72 to 0.50; P < 0.05). Conversely, for the forwards, BF and SF were significantly correlated with vertical jump height and sprint times (r: −0.62 to 0.52; P < 0.05). Clear differences exist between backs and forwards irrespective of the age category, whilst no differences were observed between U-17 and U-19 backs. The present results suggest that practitioners should monitor different body-composition variables due to the magnitude of associations observed with sprinting and jumping abilities.