Three-Compartment Body Composition in Academy and Senior Rugby League Players

Purpose: To compare the body size and 3-compartment body composition between academy and senior professional rugby league players using dual-energy X-ray absorptiometry (DXA). Methods: Academy (age 18.1 +/- 1.1 y, n = 34) and senior (age 26.2 +/- 4.6 y, n = 63) rugby league players received 1 total-body DXA scan. Height, body mass, and body-fat percentage alongside total and regional fat mass, lean mass, and bone mineral content (BMC) were compared. Independent t tests with Cohen d effect sizes and multivariate analysis of covariance (MANCOVA), controlling for height and body mass, with partial eta-squared (eta(2)) effect sizes, were used to compare total and regional body composition. Results: Senior players were taller (183.2 +/- 5.8 vs 179.2 +/- 5.7 cm, P=.001, d = 0.70) and heavier (96.5 +/- 9.3 vs 86.5 +/- 9.0 kg, P<.001, d = 1.09) with lower body-fat percentage (16.3 +/- 3.7 vs 18.0 +/- 3.7%, P=.032, d = 0.46) than academy players. MANCOVA identified significant overall main effects for total and regional body composition between academy and senior players. Senior players had lower total fat mass (P<.001, eta(2) = 0.15), greater total lean mass (P<.001, eta(2)=0.14), and greater total BMC (P=.001, eta(2)=0.12) than academy players. For regional sites, academy players had significantly greater fat mass at the legs (P<.001, eta(2)=0.29) than senior players. Conclusions: The lower age, height, body mass, and BMC of academy players suggest that these players are still developing musculoskeletal characteristics. Gradual increases in lean mass and BMC while controlling fat mass is an important consideration for practitioners working with academy rugby league players, especially in the lower body.