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Original Research

Effect of Different Between-Match Recovery Times on the Activity Profiles and Injury Rates of National Rugby League Players

Murray, Nick B.1; Gabbett, Tim J.1,2; Chamari, Karim3

Author Information
Journal of Strength and Conditioning Research: December 2014 - Volume 28 - Issue 12 - p 3476-3483
doi: 10.1519/JSC.0000000000000603
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Abstract

Introduction

A congested competition schedule, often involving multiple matches in a short period, is common in elite sporting competitions (e.g., the English Premier League). The limited recovery time between matches has the potential to have an impact on both the incidence of injury and activity profiles of match play. Recently, researchers have investigated the effect of congested competition schedules on both injury rates and activity profiles of elite level soccer players (5,7,8). Dupont et al. (8) examined the effect of 2 competitive matches in a week on injury and physical match performance. Physical activity profiles, including high-intensity distance, total distance covered, sprint distance, and number of sprints, were shown to be similar between matches, suggesting that 72–96 hours of recovery was sufficient to maintain physical performance (8). Further, Dellal et al. (7) found no differences in physical and technical activities in elite soccer players competing in congested periods of matches, and periods of no congestion.

Although it appears that a congested schedule does not alter physical performance (7,8), the effect of a congested schedule on injury rates is equivocal, with some (8), but not all (5,7), studies reporting higher injury rates with shorter between-match recovery times in elite soccer players. Dupont et al. (8) reported that the injury rates of professional soccer players were significantly higher when players played 2 matches per week, as opposed to when they played 1 match. However, these findings are in contrast to those of Carling et al. (5) who reported no association between the time interval separating matches and injury rates. Further, these authors reported no differences in injury rates after a short turnaround, compared with that reported after a long turnaround. Dellal et al. (7) also reported no differences in injury rates between matches in a congested period and matches played in a noncongested period.

Rugby league is a collision sport, played over two 40-minute halves (separated by a 10-minute half-time break). Played by 13 players (with 4 replacements) on each team, the game is intermittent in nature, and requires players to undertake bouts of high-intensity activity (e.g., running, sprinting, and tackling), interspersed with low-intensity activity (e.g., standing and walking) (18,30). Physical collisions and tackles are performed frequently throughout the game (21), resulting in a high incidence of musculoskeletal injuries (10).

Rugby league players are generally divided into positional groups (hit-up forwards, adjustables, and outside backs), reflecting positional commonality (12), with the match activity profiles shown to differ among playing positions (1,18). Recent studies have examined the repeated high-intensity effort (RHIE) demands of professional rugby league players during competitive match play (2,18). Hit-up forwards completed significantly more RHIE bouts than both adjustables and outside backs. Moreover, they experienced shorter average recovery times between bouts.

In elite rugby league match play, competition does not coincide with a standardized amount of recovery between matches; matches can be separated by as many as 10 days and as few as 5 days. Because of the intense physical demands of rugby league, players experience residual fatigue in the days after a match (27). Players have been shown to experience considerable neuromuscular and perceptual fatigue in the 24–48 hours after competition, with significant muscle damage lasting up to several days (25–27). Although individual creatine kinase responses to rugby league match play are highly variable, average concentrations of 400–500 U·L−1 have been reported in the 24 hours postmatch (29), which is comparable with values obtained after American football match play (22). In addition, positive associations have been reported between the number of collisions in which players engage and the increase in muscle soreness, perceptual and neuromuscular fatigue, and creatine kinase in response to rugby league match play, suggesting that muscle damage and fatigue can be attributed, at least in part, to repetitive blunt force trauma (29).

To date, there is limited research on the influence of different between-match recovery times on injury rates in professional rugby league (17). A second, but equally important parameter potentially affected by short between-match recovery times is the activity profiles of players. The intensity of matches, as reflected in the relative distance covered, and frequency of RHIE bouts have been shown to be significantly reduced during periods of intensified competition in junior (25) and amateur (26) players. Despite the importance of maintaining a high intensity on competitive success (13), no study has investigated the influence of different between-match recovery times on the activity profiles of elite senior rugby league players. In addition, the effect of short, medium, and long recovery between matches on the incidence of injury is unknown. Given the degree of fatigue and muscle damage that occurs in response to match play, and the extended time it takes for players to recover from the physical demands of competition, it is possible that short recovery between matches could increase the risk of injury. With this in mind, the purpose of this study was to investigate the effect of short, medium, and long between-match recovery cycles on the injury rates and activity profiles of senior elite rugby league players.

Methods

Experimental Approach to the Problem

To address our question, a prospective cohort design was used. Activity profiles were determined using commercially available microtechnology devices, and injuries resulting in a missed match were recorded. Between-match recovery cycles were defined as short (5–6 days), medium (7–8 days), and long (9–10 days) recoveries. Differences in the match activity profiles and injury rates between the 3 recovery cycles were compared using traditional null hypothesis testing and by using a practical approach based on the real-world relevance of the results (4). It was hypothesized that short recovery cycles would be associated with lower playing intensity and higher injury rates when compared with both medium and long recovery cycles.

Subjects

Forty-three elite male rugby league players from a National Rugby League (NRL) squad (mean ± SE age, 24 ± 1 years, range, 18–33 years) participated in this study. The NRL is the highest level of rugby league competition in Australia. Before data collection, the players had completed a 3 month preseason training program consisting of skills (4 sessions per week), strength and power (4 sessions per week), conditioning (2 sessions per week), and speed and agility (1 session per week) sessions. The training program focused largely on preparing players for the contact demands of competition. Consequently, selected skills and conditioning sessions were designed as “contact conditioning” sessions, to adequately prepare players for the collision and wrestling demands of match play. The players were free from injury and in peak physical condition at the commencement of the season. All participants received a clear explanation of the study, including information on the risks and benefits, and written consent was obtained. All experimental procedures were approved by the Institutional Review Board for Human Investigation.

Global Positioning System Analysis

During the season, the team played 30 matches: 3 trial matches, 24 regular season matches, and 3 finals matches. The team played 7 matches with a short turnaround (separated by 5 or 6 days), 16 matches with a medium turnaround (separated by 7 or 8 days), and 7 matches with a long turnaround (separated by 9 or 10 days). Global positioning system (GPS) analysis was completed on 31 players. Players were selected from 1 of 3 positional groups representing the adjustables (i.e., hookers, halfbacks, five-eighths, and fullbacks), hit-up forwards (i.e., props, second rowers, and locks), and outside backs (i.e., centers and wingers). The players wore the same microtechnology unit for each match, and all matches were completed during the one playing season. Matches were played in a range of environmental conditions and a range of venues.

Movement was recorded by a minimaxX GPS unit (Team 2.5; Catapult Innovations, Melbourne, Australia) sampling at 5 Hz. The GPS signal provided information on speed, distance, position, and acceleration. The GPS unit also included triaxial accelerometers and gyroscope sampling at 100 Hz, to provide greater accuracy on speed and acceleration, and information on physical collisions and RHIEs. The unit was worn in a small vest, on the upper back of the players.

Data were categorized into (a) movement speed bands, corresponding to low (0–3 m·s−1), moderate (3–5 m·s−1), and high (>5 m·s−1) speeds; (b) collisions; and (c) RHIE bouts (18). An RHIE bout was defined as ≥3 high acceleration (>2.79 m·s−2) (3), high speed, or contact efforts with <21-second recovery between efforts (12,18). The minimaxX units have been shown to have acceptable validity and reliability for estimating longer distances at walking through to striding speeds (24). Further, the minimaxX units have been shown to offer a valid measurement of tackles and repeated efforts commonly observed in collision sports (14,17).

Injury

An injury was defined as any injury that resulted in a player missing a match (i.e., match loss injury) (20). The site and type of the injury were also recorded.

Statistical Analyses

Activity Profiles

Data were checked for normality using a Shapiro–Wilk test. The distribution of the residuals was normal, each of the observations was independent, and homoscedasticity was established before analysis. Differences in the activity profiles of the 3 between-match recovery cycles and 3 positional groups were determined using a 2-way (position × recovery cycle) analysis of variance (ANOVA). Differences in the activity profiles between matches won and lost were also compared using a 2-way (match result × recovery cycle) ANOVA. A Tukey's post hoc test was used to determine the source of any significant differences. The level of significance was set at p ≤ 0.05, and all data were reported as mean ± SE. Given the practical nature of the study, magnitude-based inferential statistics were also used to determine any practically significant differences in activity profiles between positional groups, match result, and between-match recovery cycles (4). Differences between groups were analyzed using Cohen's effect size statistic (6). Effect sizes (ESs) of <0.2, 0.2–0.6, 0.61–1.2, 1.21–2.0, and >2.0 were considered trivial, small, moderate, large, and very large, respectively (23).

Incidence of Injury

Injury data were separated into the 3 between-match recovery times (i.e., short, medium, and long turnaround). Injury rates were also calculated for each positional group (i.e., adjustables, hit-up forwards, and outside backs) throughout the 3 between-match recovery times. Injury incidence was calculated by dividing the total number of injuries by the overall exposure hours for each positional group for each of the 3 between-match recovery times and expressed as rates per 1,000 hours of exposure and 95% confidence intervals (CIs). Expected injury rates were calculated as described by Phillips et al. (28). The chi-squared (χ2) test was used to determine whether the observed injury frequency was significantly different from the expected injury frequency.

Results

Activity Profiles

No significant differences (p > 0.05) were observed among different between-match recovery times for minutes played, total absolute distance covered, or the absolute distances covered at moderate and high speeds (Table 1). The mean relative distances (meters per minute) covered during match play were significantly greater (p ≤ 0.05) for short between-match recovery cycles than for both medium (15.9 ± 2.4%, 99% likely, ES = 1.13, p ≤ 0.05) and long (15.5 ± 3.0%, 99% likely, ES = 1.08, p ≤ 0.05) between-match recovery cycles. The relative distance covered at low speeds was significantly greater (p ≤ 0.05) for short between-match recovery cycles than for both medium (20.5 ± 3.1%, 99% likely, ES = 1.27, p ≤ 0.05) and long (19.6 ± 3.9%, 99% likely, ES = 1.13, p ≤ 0.05) between-match recovery cycles. The players also completed significantly more (p ≤ 0.05) RHIE bouts during long between-match recovery cycles than during medium between-match recovery cycles (79.5 ± 6.4%, 99% likely, ES = 0.83, p ≤ 0.05).

T1-21
Table 1:
Activity profiles of elite National Rugby League match play with different between-match recovery times.*†

Differences in Activity Profiles Between Positional Groups

No significant differences (p > 0.05) were observed between playing positions for relative distance covered, relative distance covered at high-speed, and RHIE frequency. Adjustables (23.3 ± 4.8%, 99% likely, ES = 0.71, p ≤ 0.05) and outside backs (53.4 ± 3.0%, 100% likely, ES = 1.16, p ≤ 0.05) covered significantly more absolute distance than hit-up forwards. Adjustables covered significantly greater relative distance at low speeds than hit-up forwards (10.9 ± 1.7%, 97% likely, ES = 0.61, p ≤ 0.05), whereas hit-up forwards (23.9 ± 1.6%, 100% likely, ES = 1.26, p ≤ 0.05) and adjustables (19.5 ± 3.3%, 99% likely, ES = 0.84, p ≤ 0.05) covered significantly more relative distance at moderate speeds than outside backs. Hit-up forwards were involved in a greater number of collisions than adjustables (40.4 ± 6.0%, 98% likely, ES = 0.58, p ≤ 0.05) and outside backs (41.0 ± 4.4, 100% likely, ES = 1.03, p ≤ 0.05) (Figure 1).

F1-21
Figure 1:
Relative distance covered (A), and distances covered in low (B), moderate (C), and high (D) speeds during elite National Rugby League match play with different between-match recovery times. Data are mean ± SE. Between-match recovery times were defined as short (5–6 days), medium (7–8 days), and long (9–10 days) turnarounds.

Activity Profiles in Matches Won and Lost

The relative distance covered was significantly greater (36.3 ± 19.8%, 99% very likely, ES ≥ 1.47, p ≤ 0.05) after short recovery cycles, when matches were won. No other differences were found among matches won and lost for any of the other recovery cycles (Figure 2).

F2-21
Figure 2:
Relative distance covered (A) and injury rates (B) when matches were won or lost during elite National Rugby League match play with different between-match recovery times. A) Data are mean ± SE. B) Data are means and 95% confidence intervals. Between-match recovery times were defined as short (5–6 days), medium (7–8 days), and long (9–10 days) turnarounds. *Significantly different (p ≤ 0.05) from all other conditions.

Incidence of Injury

Across the season, 44 injuries were recorded. No significant differences (χ2 = 0.08, df = 2, p > 0.05) were found between short (82.4 [95% CI, 31.3–133.5] per 1,000 hours), medium (86.5 [95% CI, 51.9–121.2] per 1,000 hours), and long (96.2 [95% CI, 36.6–155.8] per 1,000 hours) between-match recovery cycles for the incidence of injury.

Joint injuries were the most common type of injury sustained (27.2%), followed by hematomas (25.8%) and muscular strains (12.4%). The spinal region (14.8%) was the most commonly injured site, followed by the ankle/foot (12.9%), posterior thigh/buttock (12.0%), and shoulder (12.0%). There were significantly fewer posterior thigh and buttock injuries (χ2 = 8.43, df = 2, p ≤ 0.05) and muscular strains (χ2 = 6.16, df = 2, p ≤ 0.05) after matches with a short between-match recovery cycle.

Differences in the Incidence of Injury Between Positional Groups

The overall injury incidence varied significantly (χ2 = 6.83, df = 2, p ≤ 0.05) between positional groups (Table 2). The incidence of injury was the greatest after long between-match recovery times for outside backs and hit-up forwards. In contrast, adjustables reported greater injury rates after matches with short between-match recovery times.

T2-21
Table 2:
Injury rates of elite rugby league players among different positional groups with different between-match recovery times.*

Incidence of Injury in Matches Won and Lost

Although there was a trend toward greater injury rates during short recovery cycles when matches were lost, the differences were not significant (χ2 = 0.13, df = 5, p > 0.05) (Figure 2).

Discussion

This study is the first to investigate the effect of short, medium, and long between-match recovery cycles on activity profiles and injury rates in elite rugby league players. The results of this study demonstrate that matches after short between-match recovery cycles were associated with greater relative total distance covered than matches with longer recovery. However, this can be attributed to increases in low-speed activity, with no differences in moderate- and high-speed activity. In addition, injury incidence for different between-match recovery cycles was found to be position dependent. These findings suggest that the activity profiles of NRL match play and the injury rates of specific playing positions are influenced by the amount of recovery between matches. The differences in activity profiles and injury rates between short, medium, and long between-match recovery cycles should be considered when developing recovery strategies for professional rugby league players.

An interesting finding of this study was the significantly greater relative total distance covered during matches with short between-match recovery. The higher intensity was because of greater distances covered at low speeds. There were no notable differences in distances covered at moderate and high speeds between the different recovery cycles. Although ball-in-play time was not recorded in this study, 1 possible explanation for the greater relative distance and low-speed activity with short between-match recovery cycles is that these matches were also associated with a shorter ball-in-play time. Under these conditions, it has been shown that players increase low-speed activity and relative distance (15). Because of the limited recovery between matches, it is possible that players attempted to manage fatigue by kicking the ball out of play more often, thereby reducing ball-in-play time and maintaining low-speed activity and relative distance.

Despite the greater relative intensity exhibited in matches after a short between-match recovery cycle, RHIE frequency was lower in these matches and after matches with a medium between-match recovery cycle. The greater RHIE frequency after a long between-match recovery cycle suggests that the residual neuromuscular, endocrine, and perceptual fatigue associated with professional rugby league match play (29) may also influence RHIE frequency (25), especially for short to medium between-match recovery times. Given the suggested importance of RHIE activity to match outcome (2,13), these findings also demonstrate the performance benefits of a long between-match recovery cycle.

Although no significant differences were found between short, medium, and long between-match recovery cycles for the overall incidence of injury, when considering positional differences, an interesting trend was observed. Adjustables experienced the highest injury rate after short between-match recovery cycles, whereas the highest incidence of injury for hit-up forwards and outside backs occurred after long between-match recovery cycles. One possible explanation for the greater injury rate exhibited by adjustables during short between-match recovery cycles is that this positional group is commonly involved in greater amounts of high-speed running and collisions than other positional groups (i.e., hit-up forwards perform more collisions and less high-speed running, whereas outside backs perform greater amounts of high-speed running and are involved in fewer collisions) (18). Further, the high injury rates exhibited by outside backs after long between-match recovery cycles may be because of an increased preparedness to exert themselves to a greater extent after a greater recovery period, thus increasing the risk of soft-tissue injury. The differences in activity profiles and physical qualities (19) between positional groups coupled with the contrasting injury rates between short, medium, and long between-match recovery cycles should be considered when developing position-specific recovery strategies for professional rugby league players.

We found that the relative intensity of matches was greater after short between-match recovery cycles, and when matches were won. These results are consistent with previous findings that have shown greater relative intensity in winning teams (13). Collectively, these findings suggest that successful rugby league teams can overcome the physical and mental challenge of short between-match recovery cycles and that the competitive advantage of these teams is closely linked to their ability to maintain a higher playing intensity than their less successful counterparts (13). Although no significant associations were found between injury rates and matches won and lost, the incidence of injury during short between-match recovery cycles when matches were lost (201.9 per 1,000 hours) was approximately sixfold higher than that during short between-match recovery cycles when matches were won (34.6 per 1,000 hours). Although we cannot assume cause and effect, consistent with other high-intensity intermittent team sports (9), these results suggest that injuries may contribute to match outcome in elite rugby league match play.

There are some limitations of this study that warrant discussion. First, this study would have benefited from a larger sample of teams. Unfortunately, because of the competitive nature of professional sport, very few teams are willing to share data. This is particularly relevant for data on the activity profiles of players (obtained via GPS). To account for this limitation, we have tracked the activity profiles and injury rates of all players throughout an entire playing season, although clearly, a larger study involving all teams in the competition would have strengthened the statistical power of the results. Second, our findings should be balanced against the commercial aspects of the NRL competition. Although our findings demonstrate that injuries are more likely after short recovery turnaround periods, because of the multiple stakeholders with interests in the competition (e.g., broadcasters, corporate sponsors), it is unlikely that administrators will make changes to the recovery between matches. In this respect, these findings have important practical applications for medical personnel and strength and conditioning staff involved in the day-to-day management of players. Although these professionals have no control over the day-to-day administration of the competition, they do play an important role in player conditioning, injury prevention, and recovery. Finally, no attempt was made to quantify the training loads performed during short, medium, and long between-match recovery periods. It has previously been shown that excessive training loads are associated with an increased risk of injury (11,16). In this study, if the applied training loads were greater than tolerable, it is possible that this may have contributed to the high injury rates observed during both short and long recovery periods. Future studies examining the influence of training loads on the injury rates and match activity profiles after short, medium, and long recovery periods are warranted.

In conclusion, we documented the activity profiles and incidence of injury in professional rugby league match play and investigated the effect of short, medium, and long between-match recovery cycles on activity profiles and injury rates. The results of this study demonstrate that matches after a short recovery cycle result in a greater relative distance covered. However, this can be attributed to increases in low-speed activity, with no significant differences in moderate- and high-speed activities. In addition, the adjustables positional group had higher injury rates after short between-match recovery cycles, whereas hit-up forwards and outside backs exhibited higher injury rates after long between-match recovery cycles. The differences in activity profiles and injury rates between short, medium, and long between-match recovery cycles should be considered when developing recovery strategies for professional rugby league players.

Practical Applications

There are several practical applications from this study that are relevant to the applied sport scientist and strength and conditioning coach. First, this study demonstrates the need for position-specific (i.e., adjustables, hit-up forwards, and outside backs) recovery strategies after matches. Coaches should consider the differences in match activity profiles between positions, and adjust training loads and recovery strategies accordingly.

Second, activity profiles also varied with differing between-match recovery times. Coaches should be aware of these differences between positional groups. The continued use of GPS technology and the recording of individual injury data would allow coaches to monitor activity profiles between positions, different between-match recovery times, and differences in injury rates between specific positions.

References

1. Aughey RJ. Australian football player work rate: Evidence of fatigue and pacing?. Int J Sports Physiol Perform 5: 394–405, 2010.
2. Austin DJ, Gabbett TJ, Jenkins DG. Repeated high-intensity exercise in professional rugby league. J Strength Cond Res 25: 1898–1904, 2010.
3. Austin DJ, Kelly S. Positional differences in professional rugby league match-play through the use of global positioning systems (GPS). J Strength Cond Res 27: 14–19, 2013.
4. Batterham A, Hopkins WG. Making meaningful inferences about magnitudes. Int J Sports Physiol Perform 1: 50–57, 2006.
5. Carling C, Orhant E, LeGall F. Match injuries in professional soccer: Inter-seasonal variation and effects of competition type, match congestion and positional role. Int J Sports Med 31: 271–276, 2010.
6. Cohen J. Statistical Power Analysis for the Behavioural Sciences (2nd ed.). New York, NY: Academic Press, 1988.
7. Dellal A, Lago-Penas C, Rey E, Chamari K, Orhant E. The effects of a congested fixture period on physical performance, technical activity and injury rate during matches in a professional soccer team. Br J Sports Med 2013. In Press.
8. Dupont G, Nedelec M, McCall A, McCormack D, Berthoin S, Wisloff U. Effect of 2 soccer matches in a week on physical performance and injury rate. Am J Sports Med 38: 1752–1758, 2010.
9. Eirale C, Tol JL, Farooq A, Smiley F, Chalabi H. Low injury rate strongly correlates with team success in Qatari professional football. Br J Sports Med 47: 807–809, 2013.
10. Gabbett TJ. Incidence of injuries in junior and senior rugby league players. Sports Med 34: 849–859, 2004.
11. Gabbett TJ. Influence of training and match intensity on injuries in rugby league. J Sports Sci 22: 409–417, 2004.
12. Gabbett TJ. Sprinting patterns of national rugby league competition. J Strength Cond Res 26: 121–130, 2012.
13. Gabbett TJ. Influence of the opposing team on the physical demands of elite rugby league match play. J Strength Cond Res 27: 1629–1635, 2013.
14. Gabbett TJ. Influence of playing standard on the physical demands of professional rugby league. J Sports Sci 31: 1125–1138, 2013.
15. Gabbett TJ. Influence of ball-in-play time on the activity profiles of rugby league match-play. J Strength Cond Res 27: 1629–1635, 2013.
16. Gabbett TJ, Jenkins DG. Relationship between training load and injury in professional rugby league players. J Sci Med Sport 14: 204–209, 2011.
17. Gabbett TJ, Jenkins DG, Abernethy B. Physical collisions and injury during professional rugby league skills training. J Sci Med Sport 13: 578–583, 2010.
18. Gabbett TJ, Jenkins DG, Abernethy B. Physical demands of professional rugby league training and competition using microtechnology. J Sci Med Sport 15: 80–86, 2012.
19. Gabbett TJ, Kelly J, Ralph S, Driscoll D. Physiological and anthropometric characteristics of junior elite and sub-elite rugby league players, with special reference to starters and non-starters. J Sci Med Sport 12: 215–222, 2009.
20. Gibbs N. Injuries in professional rugby league: A three-year prospective study of the South Sydney professional Rugby league football Club. Am J Sports Med 21: 696–700, 1993.
21. Gissane C, Jennings D, Jennings S, White J, Kerr K. Physical collisions and injury rates in professional super league rugby. Cleve Med J 4: 147–155, 2001.
22. Hoffman JR, Kang J, Ratamess NA, Faigenbaum AD. Biochemical and hormonal responses during an intercollegiate football season. Med Sci Sports Exerc 37: 1237–1241, 2005.
23. Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine and exercise science. Med Sci Sports Exerc 41: 3–13, 2009.
24. Jennings D, Cormack S, Coutts AJ, Boyd L, Aughey RJ. The validity and reliability of GPS units for measuring distance in team sport specific running patterns. Int J Sports Physiol Perform 5: 328–341, 2010.
25. Johnston RD, Gabbett TJ, Jenkins DG. Influence of an intensified competition on fatigue and match performance in junior rugby league players. J Sci Med Sport 16: 460–465, 2013.
26. Johnston RD, Gibson NV, Twist C, Gabbett TJ, MacNay SA, MacFarlane NG. Physiological responses to an intensified period of Rugby League competition. J Strength Cond Res 27: 643–654, 2013.
27. McLellan C, Lovell DG. Markers of postmatch fatigue in professional Rugby League players. J Strength Cond Res 4: 1030–1039, 2011.
28. Phillips LH, Standen PJ, Batt ME. Effects of seasonal change in rugby league on the incidence of injury. Br J Sports Med 32: 144–148, 1998.
29. Twist C, Waldron M, Highton J, Burt D, Daniels M. Neuromuscular, biochemical and perceptual post-match fatigue in professional rugby league forwards and backs. J Sports Sci 30: 359–367, 2012.
30. Waldron M, Twist C, Highton J, Worsfold P, Daniels M. Movement and physiological match demands of elite rugby league using portable global positioning systems. J Sports Sci 29: 1223–1230, 2011.
Keywords:

physical demands; collision sport; training; injury risk

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