Preseason Body Composition Adaptations in Elite Caucasian and Polynesian Rugby Union Athletes

During pre-season training, rugby union (RU) athletes endeavour to enhance physical performance characteristics that are aligned with on-field success. Specific physique traits are associated with performance, therefore body composition assessment is routinely undertaken in elite environments. This study aimed to quantify pre-season physique changes in elite RU athletes with unique morphology and divergent ethnicity. Twenty-two Caucasian and Polynesian professional RU athletes received dual-energy X-ray absorptiometry (DXA) assessments at the beginning and conclusion of an 11-week pre-season. Interactions between on-field playing position and ethnicity in body composition adaptations were explored, and the least significant change (LSC) model was used to evaluate variations at the individual level. There were no combined interaction effects with the variables position and ethnicity, and any body composition measure. After accounting for baseline body composition, Caucasians gained more lean mass during the pre-season than Polynesians (2425 ± 1303 g vs 1115 ± 1169 g; F=5.4, p=0.03). Significant main effects of time were found for whole body and all regional measures with fat mass decreasing (F=31.1–52.0, p<0.01), and lean mass increasing (F=12.0–40.4, p