A Comparison of Body Composition Between Elite and Sub-elite Rugby Union Players: An Observational Study

Abstract

Introduction: The assessment of body composition in athletes has become frequently used in practice as it is assumed to be an important determinant for athletic performance. Dual energy X-ray absorptiometry (DXA), a three-compartment model which assesses body composition in the form of bone mineral content, lean mass and fat mass, has quickly become the gold-standard measurement of body composition in athletic populations. The aim of this study was to compare body composition and anthropometric measurements between elite and national and development level rugby union players to examine if elite players possess more fat mass, muscle mass and bone content compared to national and development level players due to a higher participation level.

Methods: Demographic (age) and basic anthropometric data (stature, mass) were collected in 56 male rugby players (n=38 elite and n=18 national and development). Body composition outcomes were assessed from total-body less head (TBLH) DXA scans (Lunar iDXA, GE Healthcare (Madison, WI) taken during the preseason. The chosen significance level was p = 0.05 and the confidence interval was 95%. Two-way ANOVA tests were used to identify potential significance between the elite and national and developmental players as well as between the two positional groups (forwards and backs).

Results: The elite players were significantly older (24 vs 20 years; p=0.001) and displayed significantly greater amounts of trunk total mass (47.8 ± 6.8 vs 43.4 ± 4.8 kg; p = 0.005) compared to national and developmental players. Forwards possessed greater stature (190.1 ± 6.5 vs 180.3 ± 5.2 cm; p <0.001) and body mass (112.6 ± 15.3 vs 89.4 ± 8.2 kg; p<0.001) compared to backs. Forwards also have greater arm (14.3 ± 1.1 vs 11.7 ± 1.2 kg; p <0.001), leg (38.8 ± 3.5 vs 31.2 ± 3.4 kg; p <0.001), trunk (51.7 ± 4.7 vs 41.6 ± 3.7 kg; p <0.001) and TBLH (104.8 ± 8.1 vs 84.6 ± 8.0 kg; p <0.001) total mass. Forwards possessed greater lean mass in the arms (10.9 ± 1.5 kg; p <0.001), legs (28.5 ± 2.3 vs 24.2 ± 2.9 kg; p <0.001) trunk (36.6 ± 2.8 vs 32.8 ± 3.4 kg; p <0.001) and TBLH (76.2 ± 5.0 vs 66.5 ± 7.1 kg; p <0.001) regions. Forwards reported a greater difference in right leg (14.4 ± 1.1 vs 12.2 ± 15 kg; p <0.001) and left leg (14.1 ± 1.2 vs 11.9 ± 1.4 kg; p <0.001) lean mass. Forwards showed greater fat mass in the arms (18.5 ± 3.9 vs 14.7 ± 3.2 %; p <0.001), legs (21.7 ± 4.4 vs 17.4 ± 3.7 %; p <0.001), trunk (25.6 vs 6.2 vs 18.1 ± 4.5 %; p <0.001) and TBLH (23.2 ± 4.7 vs 17.4 ± 3.9 %; p <0.001) regions than backs. Forwards also reported greater TBLH bone mass (4.02 ± 0.44 vs 3.52 kg; p <0.001), BMD (1.56 vs 0.08 vs 1.46 ± 0.09 kg; p<0.001) and BMC (4.02 ± 0.44 vs 3.52 kg; p <0.001) than backs.

Conclusion: Elite players were older and possessed greater trunk total mass compared to the national and developmental players. The lack of differences in terms of body composition between the elite and national and developmental groups was likely due to the high level of performance of the national level players as many were close to making the transition to the elite level. In terms of playing position, forwards were greater in stature and possessed more body mass than backs. Forwards were found to have greater amounts of arms, legs, trunk and TBLH total mass, lean mass and fat mass compared to backs. Forwards also showed greater differences in right and left leg lean mass than backs and greater TBLH bone mass, TBLH bone mineral density and content. These findings indicate that playing position may be a greater determinant of body composition than playing level.