Movement demands and running intensities of semi-professional rugby league players during A 9's tournament: a case study.

Author:Inglis, Paul
Position::Research article - Report
 
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Introduction

Rugby league is a collision sport consisting of intermittent bursts of high intensity activity (e.g., sprinting, change of direction, and tackling) and low intensity activity (e.g., walking, jogging and standing) (Gabbett, 2005), played on a grass surface (100 meters long by 68 meters wide) by two teams of 13 players, with an additional four interchange players. A team consists of two main playing groups, these being forwards and backs, which may further be categorized as (i) adjustables (full-back, five-eight, half-back, hooker); (ii) outside backs (winger, center); (iii) edge forwards (second-row, lock); and (iv) core forwards (front row). A rugby league match duration is 80-minutes comprising two 40-minute halves with a 10-minute break in between. During the match both teams are permitted a maximum of eight interchanges from players that are on the interchange bench. Depending on playing position and playing level, players have been reported to cover distance up to 8500 meters per game (Hausler et al., 2016).

A modified version of the game, called rugby league 9's (RL9's) involves two teams of nine players on the field and six players on the interchange bench. A RL9's game is played over two 9-minute halves with a 2-minute break on a full sized playing field (Kempton and Coutts, 2015). Unlike the traditional version of rugby league, during a RL9's match teams are allowed unlimited interchanges from the bench players. The unique characteristics of the RL9's format, with fewer players on a full size field, shorter playing halves and unlimited interchanges results in higher running intensities compared to the traditional format, with professional rugby league players reported to cover up to 1529 meters in a single 9's game (Kempton and Coutts, 2015).

During a rugby league season players compete on a weekly basis over a 6-month period with 5-9 days between matches. Studies from rugby league (Johnston et al., 2013a; 2013b) and other team sports (Gescheit et al., 2015; Montgomery et al., 2008; Rowsell et al., 2011; Spencer et al., 2005) have found that during intensified competitions with less than 5 days between games both playing performances and match intensities are reduced, which may be due, in part, to the accumulative effects of residual fatigue. Johnson et al. (2013) reported reductions in high-intensity activities and work-rates during an intensified junior rugby league competition and suggested that this was due to fatigue and muscle damage accumulated over the course of the tournament. Additionally, a series of studies by McLellan and colleagues (2011a; 2011b; 2012) demonstrated that following match-play neuromuscular function is compromised for up to 2 days and skeletal muscle damage is elevated for 5 days in elite rugby league players.

Typically, a 9's tournament runs over consecutive days with multiple games (6-7) played with 1-3 hour break between games. It has yet to be elucidated what effect a 9's tournament has on running intensities, as to date no studies have yet provided information on the physical demands of semi-professional rugby league players under the 9's format. Therefore, the aim of the current study was to report the physical demands and running intensities of semi-professional rugby league players during a 9's tournament and describe the magnitude of change of these variables over the course of the tournament. It is hypothesized that running intensities would be reduced over the course of the tournament, and these reductions would be position-related (Suarez-Arrones et al., 2014).

Methods

Subjects

Six male rugby league players (mean [+ or -] SD; age 23.2 [+ or -] 2.1 yrs., height 1.84 [+ or -] 0.06 m, weight 93.2 [+ or -] 13.4 kg) were recruited from a semi-professional rugby league team competing in the Queensland Cup competition (Australia). Players were categorized into playing positions of either adjustables (n = 2), outside backs (n = 2) or forwards (n = 2). Data was collected during the 2016 preseason 9's tournament consisting of five group matches, one final match (5 wins and 1 loss; RL9's Tournament Winners) over two days, with three matches played on day 1 and three on day 2 (six matches in total). All players participated in every match with a total of 36 individual players' match files obtained for analysis. Informed consent and ethics approval were obtained before data collection.

Study design

This case study used observational quasi-experimental design where subjects acted as their own control, with GPS data collected from semi-professional rugby league players who competed in a RL9's tournament over a two-day period. The RL9's tournament was played during the 2016 pre-season (three weeks before round 1 of the regular season and 12 weeks into preseason training) and involved both semi-professional and amateur rugby league players. Each match was 18 minutes (2 x 9 minute halves) in duration with a 2-minute half time break. The GPS data was collected during three matches on day 1 and day 2, respectively, with the last game on day 2 being the RL9's Tournament Final. All matches were played during fine and dry conditions (mean; temperature: 31.6[degrees]C; humidity: 63%) on a natural grass surface. A standardized recovery protocol (Harrington, 2016) was completed by all players after the final game on day 1 and consisted of lower-body cold water immersion (Ice bath: 12[degrees]C for 8 minutes); foam roller self-myofascial release (8 minutes); and lower-body massage (8 minutes). Players were also...

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