Rugby league is a contact team sport performed at an average intensity similar to that of other team sports (~70–80% VO2max), made up of unsystematic movements of varying type, duration, and frequency. The high number of collisions, repeated eccentric muscle contractions associated with accelerating and decelerating, and prolonged aerobic nature of rugby league matches result in the development of fatigue in the days after exercise. Monitoring the presence and magnitude of this fatigue to maximize performance and training adaptation is an important consideration for applied sports scientists. Several methods have been proposed to measure the magnitude of fatigue in athletes. Perceptual measures (eg, questionnaires) are easy to employ and are sensitive to changes in performance. However, the subjective nature of such measures should be considered. Blood biochemical markers of fatigue may provide a more objective measure of homeostatic disturbances associated with fatigue; however, the cost, level of expertise required, and high degree of variability of many of these measures often preclude them from being used in the applied setting. Accordingly, simple measure of muscle function (eg, jump height) and simulated performance offer the most practical and appropriate method of determining the extent of fatigue experienced by rugby league players. A meaningful change in each measure of fatigue for the monitoring of players can be easily determined, provided that the reliability of the measure is known. Multiplying the coefficient of variation by 0.3, 0.9, and 1.6 can be used to determine a small, moderate, and large change, respectively.
Craig Twist and Jamie Highton
Jamie Highton, Thomas Mullen, and Craig Twist
To examine the influence of knowledge of exercise duration on pacing and performance during simulated rugby league match play.
Thirteen male university rugby players completed 3 simulated rugby league matches (RLMSP-i) on separate days in a random order. In a control trial, participants were informed that they would be performing 2 × 23-min bouts (separated by 20 min) of the RLMSP-i (CON). In a second trial, participants were informed that they would be performing 1 × 23-min bout of the protocol but were then asked to perform another 23-min bout (DEC). In a third trial, participants were not informed of the exercise duration and performed 2 × 23-min bouts (UN).
Distance covered and high-intensity running were higher in CON (4813 ± 167 m, 26 ± 4.1 m/min) than DEC (4764 ± 112 m, 25.2 ± 2.8 m/min) and UN (4744 ± 131 m, 24.4 m/min). Compared with CON, high-intensity running and peak speed were typically higher for DEC in bout 1 and lower in bout 2 of the RLMSP-i, while UN was generally lower throughout. Similarly, DEC resulted in an increased heart rate, blood lactate, and rating of perceived exertion than CON in bout 1, whereas these variables were lower throughout the protocol in UN.
Pacing and performance during simulated rugby league match play depend on an accurate understanding of the exercise endpoint. Applied practitioners should consider informing players of their likely exercise duration to maximize running.
Thomas Mullen, Jamie Highton, and Craig Twist
It is important to understand the extent to which physical contact changes the internal and external load during rugby simulations that aim to replicate the demands of match play. Accordingly, this study examined the role of physical contact on the physiological and perceptual demands during and immediately after a simulated rugby league match. Nineteen male rugby players completed a contact (CON) and a noncontact (NCON) version of the rugby league match-simulation protocol in a randomized crossover design with 1 wk between trials. Relative distance covered (ES = 1.27; ±0.29), low-intensity activity (ES = 1.13; ±0.31), high-intensity running (ES = 0.49; ±0.34), heart rate (ES = 0.52; ±0.35), blood lactate concentration (ES = 0.78; ±0.34), rating of perceived exertion (RPE) (ES = 0.72; ±0.38), and session RPE (ES = 1.45; ±0.51) were all higher in the CON than in the NCON trial. However, peak speeds were lower in the CON trial (ES = −0.99; ±0.40) despite unclear reductions in knee-extensor (ES = 0.19; ±0.40) and -flexor (ES = 0.07; ±0.43) torque. Muscle soreness was also greater after CON than in the NCON trial (ES = 0.97; ±0.55). The addition of physical contact to the movement demands of a simulated rugby league match increases many of the external and internal demands but also results in players’ slowing their peak running speed during sprints. These findings highlight the importance of including contacts in simulation protocols and training practices designed to replicate the demands of real match play.
Mark Waldron, Jamie Highton, and Craig Twist
This study assessed the reliability of a rugby league movement-simulation protocol, relative to interchanged players (RLMSP-i).
Fifteen male participants completed 2 trials of the RLMSP-i, separated by 1 wk. The RLMSP-i comprised low- to moderate-intensity running, interspersed by high-intensity sprinting and tackling activity, based on global positioning system (GPS) data recorded during Super League performances.
The lowest coefficient of variation (CV ± 95% CI) was observed for total m/min during both interchange bout 1 (1.1% ± 0.2%) and bout 2 (1.0% ± 0.2%). The percentage of heart rate peak and ratings of perceived exertion demonstrated CVs of 1.2–2.0% and 2.9–3.5%, respectively. The poorest agreement between trials was found for blood lactate concentration (16.2% ± 2.8%). In no case was the CV smaller than the smallest worthwhile change, yet in every case the moderate changes were larger than the CV.
The RLMSP-i’s reliability is sufficient to enable the detection of moderate changes in various performance and physiological measurements that accurately simulate some, but not all, aspects of rugby league matches.
Jonathan P. Norris, Jamie Highton, and Craig Twist
Purpose: To assess the reliability and external validity of a rugby league movement-simulation protocol for interchange players (RLMSP-i) that was adapted to include physical contact between participants. Methods: A total of 18 rugby players performed 2 trials of a modified RLMSP-i, 7 d apart. The simulation was conducted outdoors on artificial turf with movement speeds controlled using an audio signal. Microtechnology was used to measure locomotive and accelerometer (ie, PlayerLoad™) metrics for both bouts (∼23 min each) alongside heart rate (HR) and rating of perceived exertion (RPE). Results: Reported for each bout, total distance (102  m·min−1 and 101  m·min−1), low-speed distance (77  m·min−1 and 79  m·min−1), high-speed distance (25  m·min−1 and 22  m·min−1), PlayerLoad (10  AU·min−1 and 10  AU·min−1), PlayerLoad slow (3.2 [0.6] AU·min−1 and 3.2 [0.6] AU·min−1), 2-dimensional PlayerLoad (6.0 [0.9] AU·min−1 and 5.7 [0.8] AU·min−1), and HR (86 %HRmax and 84 %HRmax) were similar to match play. The coefficient of variation (CV%) for locomotive metrics ranged from 1.3% to 14.4%, accelerometer CV% 4.4% to 10.0%, and internal load 4.8% to 13.7%. All variables presented a CV% less than the calculated moderate change during 1 or both bouts of the simulation except high-speed distance, percentage of the participant’s peak HR, and RPE. Conclusion: The modified RLMSP-i offers a reliable simulation to investigate influences of training and nutrition interventions on the movement and collision activities of rugby league interchange players.
Thomas Mullen, Craig Twist, and Jamie Highton
Purpose: To examine responses to a simulated rugby league protocol designed to include more stochastic commands, and therefore require greater vigilance, than traditional team-sport simulation protocols. Methods: Eleven male university rugby players completed 2 trials (randomized and control [CON]) of a rugby league movement simulation protocol, separated by 7 to 10 d. The CON trial consisted of 48 repeated ∼115-s cycles of activity. The stochastic simulation (STOCH) was matched for the number and types of activity performed every 5.45 min in CON but included no repeated cycles of activity. Movement using GPS, heart rate, rating of perceived exertion, and Stroop test performance was assessed throughout. Maximum voluntary contraction peak torque, voluntary activation (in percentage), and global task load were assessed after exercise. Results: The mean mental demand of STOCH was higher than CON (effect size [ES] = 0.56; ±0.69). Mean sprint speed was higher in STOCH (22.5 [1.4] vs 21.6 [1.6] km·h−1, ES = 0.50; ±0.55), which was accompanied by a higher rating of perceived exertion (14.3 [1.0] vs 13.0 [1.4], ES = 0.87; ±0.67) and a greater number of errors in the Stroop test (10.3 [2.5] vs 9.3 [1.4] errors; ES = 0.65; ±0.83). Maximum voluntary contraction peak torque (CON = −48.4 [31.6] N·m and STOCH = −39.6 [36.6] N·m) and voluntary activation (CON = −8.3% [4.8%] and STOCH = −6.0% [4.1%]) was similarly reduced in both trials. Conclusions: Providing more stochastic commands, which requires greater vigilance, might alter performance and associated physiological, perceptual, and cognitive responses to team-sport simulations.
Mark Waldron, Jamie Highton, Matthew Daniels, and Craig Twist
This study aimed to quantify changes in heart rate (HR) and movement speeds in interchanged and whole-match players during 35 elite rugby league performances.
Performances were separated into whole match, interchange bout 1, and interchange bout 2 and further subdivided into match quartiles. Mean percentages of peak HR (%HRpeak) and total and high-intensity running (> 14 km/h) meters per minute (m/min) were recorded.
For whole-match players, a decline in high-intensity m/min and %HRpeak was observed between successive quartiles (P < .05). High-intensity m/min during interchange 1 also progressively declined, although initial m/min was higher than whole match (24.2 ± 7.9 m/min vs 18.3 ± 4.7 m/min, P = .018), and %HRpeak did not change over match quartiles (P > .05). During interchange 2, there was a decline in high-intensity m/min from quartile 1 to quartile 3 (18 ± 4.1 vs 13.4 ± 5 m/min, P = .048) before increasing in quartile 4. Quartiles 1 and 2 also showed an increase in %HRpeak (85.2 ± 6.5 vs 87.3 ± 4.2%, P = .022).
Replacement players adopted a high initial intensity in their first match quartile before a severe decline thereafter. However, in a second bout, lower exercise intensity at the outset enabled a higher physiological exertion for later periods. These findings inform interchange strategy and conditioning for coaches while also providing preliminary evidence of pacing in team sport.
Nick Dobbin, Cari Thorpe, Jamie Highton, and Craig Twist
Purpose: To examine the within- and between-sexes physical performance, well-being, and neuromuscular function responses across a 4-day international touch rugby (Touch) tournament. Methods: Twenty-one males and 20 females completed measures of well-being (fatigue, soreness, sleep, mood, and stress) and neuromuscular function (countermovement jump height, peak power output, and peak force) during a 4-day tournament with internal, external, and perceptual loads recorded for all matches. Results: Relative and absolute total, low-intensity (females), and high-intensity distance were lower on day 3 (males and females) (effect size [ES] = −0.37 to −0.71) compared with day 1. Mean heart rate was possibly to most likely lower during the tournament (except day 2 males; ES = −0.36 to −0.74), whereas rating of perceived exertion-training load was consistently higher in females (ES = 0.02 to 0.83). The change in mean fatigue, soreness, and overall well-being was unclear to most likely lower (ES = −0.33 to −1.90) across the tournament for both sexes, with greater perceived fatigue and soreness in females on days 3 to 4 (ES = 0.39 to 0.78). Jump height and peak power output were possibly to most likely lower across days 2 to 4 (ES = −0.30 to −0.84), with greater reductions in females (ES = 0.21 to 0.66). Well-being, countermovement jump height, and peak force were associated with changes in external, internal, and perceptual measures of load across the tournament (η 2 = −.37 to .39). Conclusions: Elite Touch players experience reductions in well-being, neuromuscular function, and running performance across a 4-day tournament, with notable differences in fatigue and running between males and females, suggesting that sex-specific monitoring and intervention strategies are necessary.
Nick Dobbin, Jamie Highton, Samantha L. Moss, and Craig Twist
Purpose: To determine the utility of running-only and rugby-specific, in-season sprint interval interventions in professional rugby league players. Methods: Thirty-one professional academy rugby players were assigned to a rugby-specific (SITr/s, n = 16) or running-only (SITr, n = 15) sprint interval training group. Measures of speed, power, change of direction ability, prone Yo-Yo Intermittent Recovery Test (Yo-Yo IR1) performance, and heart rate recovery were taken before and after the 2-week intervention as were submaximal responses to the prone Yo-Yo IR1. Internal, external, and perceptual responses were collected during SITr/s and SITr, with well-being and neuromuscular function assessed before each session. Results: Despite contrasting (possible to most likely) internal, external, and perceptual responses to the SIT interventions, possible to most likely within-group improvements in physical characteristics, heart rate recovery, and submaximal responses to the prone Yo-Yo IR1 were observed after both interventions. Between-group analysis favored the SITr/s intervention (trivial to moderate) for changes in 10-m sprint time, countermovement jump, change of direction, and medicine ball throw as well as submaximal (280–440 m) high metabolic power, PlayerLoad™, and acceleration distance during the prone Yo-Yo IR1. Overall changes in well-being or neuromuscular function were unclear. Conclusions: Two weeks of SITr/s and SITr were effective for improving physical characteristics, heart rate recovery, and submaximal responses to the prone Yo-Yo IR1, with no clear change in well-being and neuromuscular function. Between-group analysis favored the SITr/s group, suggesting that the inclusion of sport-specific actions should be considered for in-season conditioning of rugby league players.
Chelsea L. Oxendale, Craig Twist, Matthew Daniels, and Jamie Highton
While exercise-induced muscle damage (EIMD) after rugby league match play has been well documented, the specific match actions that contribute to EIMD are unclear. Accordingly, the purpose of this study was to investigate the positional demands of elite rugby league matches and examine their relationship with subsequent EIMD.
Twenty-eight performances (from 17 participants) were captured using 10-Hz global positioning systems over 4 competitive matches. Upper- and lower-body neuromuscular fatigue, creatine kinase (CK), and perceived muscle soreness were assessed 24 h before and at 12, 36, and 60 h after matches.
High-intensity running was moderately higher in backs (6.6 ± 2.6 m/min) than in forwards (5.1 ± 1.6 m/min), whereas total collisions were moderately lower (31.1 ± 13.1 vs 54.1 ± 37.0). Duration (r = .90, CI: .77–.96) and total (r = .86, CI: .70–.95) and high-intensity distance covered (r = .76, CI: .51–.91) were associated (P < .05) with increased CK concentration postmatch. Total collisions and repeated high-intensity efforts were associated (P < .05) with large decrements in upper-body neuromuscular performance (r = –.48, CI: –.74 to .02; r = –.49, CI: –.77 to .05, respectively), muscle soreness (r = –.68, CI: –.87 to –.10, r = –.66, CI: –.89 to .21, respectively), and CK concentration (r = .67, CI: .42–.85; r = .73, CI: .51–.87, respectively). All EIMD markers returned to baseline within 60 h.
Match duration, high-intensity running, and collisions were associated with variations in EIMD markers, suggesting that recovery is dependent on individual match demands.