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.
NAR, Nucleus of High Performance in Sport, São Paulo, SP, Brazil - fabioy_nakamura@yahoo.com.br.|State University of Londrina, Londrina, PR, Brazil - fabioy_nakamura@yahoo.com.br.
Fábio Y
FY
Nakamura
NAR, Nucleus of High Performance in Sport, São Paulo, SP, Brazil.
Lucas A
LA
Pereira
Brazilian Rugby Confederation, São Paulo, SP, Brazil.
José E
JE
Moraes
NAR, Nucleus of High Performance in Sport, São Paulo, SP, Brazil.
Ronaldo
R
Kobal
NAR, Nucleus of High Performance in Sport, São Paulo, SP, Brazil.
Katia
K
Kitamura
NAR, Nucleus of High Performance in Sport, São Paulo, SP, Brazil.
Cesar C
CC
Cal Abad
University Tras-os-Montes e Alto Douro, Research Center in Sports Sciences, Health and Human Development (CIDESD), Vila Real, Portugal.
Luís M
LM
Teixeira Vaz
NAR, Nucleus of High Performance in Sport, São Paulo, SP, Brazil.
Irineu
I
Loturco
D000328:Adult; D001938:Brazil; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology / Q000523:psychology*; D005080:Exercise Test / Q000379:methods; D005538:Football / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010807:Physical Endurance / Q000502:physiology; D055815:Young Adult