RUGBY UNION MOVEMENT PATTERNS: THE IMPACT OF FORWARD SUBSTITUTES

PURPOSE: Forwards are regularly substituted within the sport of rugby union. There is currently limited information on how this effects movement patterns in rugby union match play. This study investigated how the movement patterns and pacing strategies of forwards that play the whole game in contrast with forwards inserted as substitutes in the second half. METHODS: Global positioning system (GPS) data were collected during professional rugby union match play. Second half data for 19 whole game (WG) players and 17 substitute (sub) players were compared in terms of relative total and high-intensity (>4m.s-1) distance, maximum speed (m.sec-1), sprint (>6 m.s-1) and acceleration (>2.75 m.s-1) frequency. Given the practical nature of this study, likelihood of effects being true was assessed via magnitude-based inference and the size of effect was assessed using Cohen’s effect size (ES) statistic. Effect sizes of 0.2, 0.6, 1.2 and 2.0 were considered small, medium, large and very large respectively. RESULTS: Substitute forwards displayed increased high intensity running distance (12 ± 6 vs. 9 ± 4 m.min-1, likely medium), sprint frequency (1 every 13 ± 25 min vs. 1 every 20 ± 25 min, likely medium), acceleration frequency (1 every 7 ± 9 min vs. 1 every 13 ± 7 min, likely small) vs. whole game players. Differences in movement variables were larger when substitutes were first introduced, but decreased were not different in later quartiles. CONCLUSIONS: Whole game players adopted a “flat” pacing strategy in the second half, while substitutes adopted a “one bout, all out” approach. The impact if substitutes on game movement patterns is meaningful, but short-lived. Differences between whole game and substitute players were were negligible in the latter phases of the game. PRACTICAL APPLICATION: The introduction of forward substitutes increases match intensity temporarily. This effect could be accentuated by introducing multiple substitutes at once, and ay have tactical applications with coaches saving their substitutes for critical moments within the game

Movement and Impact Characteristics of South African Professional Rugby Union Players

Background. Global positioning system (GPS) technology can provide accurate, non-invasive, real-time movement analysis of players participating in team sports. The application of this technology to rugby union will improve training practices by allowing improved understanding of movement characteristics and more individualised programmes. Objectives. To characterise the movement and impact patterns of South African professional rugby union players during match play and compare these to previously reported data. Methods. Nineteen professional rugby players were tracked using GPS systems during 24 matches during the 2013 rugby season. Players were grouped as (i) backs or forwards and (ii) tight forwards, loose forwards, scrumhalves, inside backs or outside backs. Movements were categorised in speed zones corresponding to walking (0 - 2 m.s-¹), jogging (2 - 4 m.s-¹), striding (4 - 6 m.s-¹) and sprinting (>6 m.s-¹). Walking and jogging were classified as low-intensity and striding and sprinting as high-intensity movement zones. An inbuilt triaxial accelerometer (sampling frequency 100 Hz) measured the total impacts >5G and high-intensity impacts >8G. All data were normalised to time on field and reported as mean (standard deviation). Results. There was no difference between forwards and backs in relative distance covered. Backs reached higher maximum speeds than forwards (backs 8.8 (1.1) v. forwards 7.6 (1.3) m.s-¹, effect size (ES) 1.0, and outside backs were the fastest positional group (9.4 (0.9) m.s-¹, ES 0.4 - 2.2). Players in all positions spent the majority of time walking (79 - 84%). Backs covered more distance than forwards in high-intensity speed zones (forwards 11 (5) v. backs 14 (4) m.min-¹, ES 0.7). Tight forwards covered the most distance in low-intensity zones (63 (6) m.min-1, ES 0.3 - 1.7) while scrumhalves ran the most distance in high-intensity zones (20 (5) m.min-¹, ES 1.2 - 3.6). High-intensity : low-intensity running ratios ranged from 1:13 (tight forwards) to 1:3 (scrumhalves). Loose forwards and inside backs exhibited similar movement patterns. There was no difference in impact variables between forwards and backs. Inside backs sustained the least total impacts (6.5 (1.2) >5G.min-¹, ES 0.9 - 2.0) and high-intensity impacts (0.7 (0.2) >8G.min-¹, ES 0.5 - 1.4). Conclusions. There were notable differences in the movement of professional rugby union players in different positions, and effective training programmes should reflect these variations

Effects of an intensifed competition period on neuromuscular function in youth rugby union players

Playing rugby union matches causes a number of fatigue responses, including reduced lower body neuromuscular function (NMF) (commonly measured by counter movement jump (CMJ))(1). The time course of this response following match play is well established in professional (2) and academy (3) level rugby union players, who take at least 60 hours for NMF to recover. No data exist for high school level rugby union players, but these players are often exposed to multiple game tournaments and festivals (2 games in 3 days, or 3 games in 5 days) within their competition structures. Aim. The aim of this case study is to document the NMF response to playing three rugby union matches within five days. This will provide useful information to practitioners who must manage fatigue and recovery of youth rugby union players who play multiple games within short time periods

Metabolic consequences of exercise-induced muscle damage.

Exercise-induced muscle damage (EIMD) is commonly experienced following either a bout of unaccustomed physical activity or following physical activity of greater than normal duration or intensity. The mechanistic factor responsible for the initiation of EIMD is not known; however, it is hypothesised to be either mechanical or metabolic in nature. The mechanical stress hypothesis states that EIMD is the result of physical stress upon the muscle fibre. In contrast, the metabolic stress model predicts that EIMD is the result of metabolic deficiencies, possibly through the decreased action of Ca(2+)-adenosine triphosphatase. Irrespective of the cause of the damage, EIMD has a number of profound metabolic effects. The most notable metabolic effects of EIMD are decreased insulin sensitivity, prolonged glycogen depletion and an increase in metabolic rate both at rest and during exercise. Based on current knowledge regarding the effects that various types of damaging exercise have on muscle metabolism, a new model for the initiation of EIMD is proposed. This model states that damage initiation may be either metabolic or mechanical, or a combination of both, depending on the mode, intensity and duration of exercise and the training status of the individual