Physical and physiological differences of backs and forwards from the Brazilian National rugby union team.

BACKGROUND: The aim of this study was to compare backs and forwards rugby union players recruited to a National team in the following physical and physiological indicators: anthropometrics, squat jump (SJ), countermovement jump (CMJ), 10- and 30-meter sprint, resting heart rate variability (HRV), Yo-Yo Test and heart rate (HR) at 2 minutes of test.

METHODS: The measurements were performed on the first day of a training camp planned to finely select the players who would participate in the 2016 America's Rugby Championship. The magnitude-based inference was used in the comparisons.

RESULTS: Backs demonstrated almost certainly greater distance in the Yo-Yo Test (backs: 2305.9±231.3 meters; forwards: 1802.4±361.2 meters), higher vertical jump height in both SJ and CMJ (SJ: 44.0±5.3 cm vs. 37.6±5.4 cm; CMJ: 46.1±5.0 cm vs. 40.0±5.5 cm, for backs and forwards respectively), and superior sprint velocity in 10- and 30-m (10-m: 6.02±0.23 m.s-1 vs. 5.51±0.34 m.s-1; 30-m: 7.46±0.25 m.s-1 vs. 6.89±0.37 m.s-1, for backs and forwards respectively) than the forwards. In contrast, forwards were almost certainly taller and heavier than backs, and displayed higher sprint momentum in 10- and 30-meters (10 meters: 513.0±51.6 kg.m.s-1 vs. 598.4±53.1 kg.m.s-1; 30 meters: 635.3±56.1 kg.m.s-1 vs. 749.0±70.5 kg.m.s-1, for backs and forwards respectively). The submaximal HR in the first 2-minutes of the Yo-Yo test was likely lower in the backs than in the forwards (77.6±5.1% of the maximal HR vs. 81.3±5.4% of the maximal HR for backs and forwards respectively), while HRV indices were not different between backs and forwards.

CONCLUSIONS: Playing position appears to be determined by the players' physical and physiological characteristics in top-level rugby union, and the submaximal HR measured during Yo-Yo test can be a simple alternative to discriminate backs and forwards.