Jamie Highton

Movement and physiological match demands of elite rugby league using portable global positioning systems

Abstract Twelve elite players from an English Super League club consented to participate in the present study using portable global positioning system (GPS) devices to assess position-specific demands. Distances covered at low-intensity running, moderate-intensity running, high-intensity running, very high-intensity running, and total distance were significantly (P < 0.05) lower in forwards compared with outside backs and adjustables. Metres per minute was higher in adjustables and forwards, owing to higher values for relative distance in medium-intensity running and a rise in high-intensity running from previous absolute values. Sprint distance, sprint frequency, and peak speed were higher in outside backs than both adjustables and forwards. A moderate, significant correlation (r = 0.62, P = 0.001) was apparent between session ratings of perceived exertion and summated heart rate. Results support the requirement for position-specific conditioning and provide preliminary evidence for the use of session ratings of perceived exertion as a measure of match load.

Neuromuscular, biochemical and perceptual post-match fatigue in professional rugby league forwards and backs

Abstract In this study, we investigated changes in creatine kinase, perceptual and neuromuscular fatigue of professional rugby league players after match-play. Twenty-three male rugby league players (10 backs, 13 forwards) had their creatine kinase, perceptual ratings of fatigue, attitude to training, muscle soreness, and flight time in a countermovement jump measured before and 1 and 2 days after (day 1 and day 2 respectively) league matches. Total playing time, offensive and defensive contacts were also recorded for each player. Creatine kinase was higher both 1 and 2 days after than before matches (P < 0.05) in forwards and backs. Similarly, perceived fatigue and muscle soreness were higher than pre-match on both days 1 and 2 (P < 0.05), but did not differ between groups (P > 0.05). Jump performance was lower on day 1 but not day 2 for both groups (P < 0.05). While total playing time was longer in backs (P < 0.05), relative frequencies for all contacts were greater in forwards (P < 0.05). Contacts for forwards were correlated with all markers of fatigue (P < 0.05), but only flight time was correlated with offensive contacts in backs (P < 0.05). Despite the mechanisms of fatigue being different between forwards and backs, our results highlight the multidimensional nature of fatigue after a rugby league match and that these markers do not differ between positions.

Fatigue and Pacing in High-Intensity Intermittent Team Sport: An Update

With the advancements in player tracking technology, the topic of fatigue and pacing in team sport has become increasingly popular in recent years. Initially based upon a pre-conceived pacing schema, a central metabolic control system is proposed to guide the movement of players during team sport matches, which can be consciously modified based on afferent signals from the various physiological systems and in response to environmental cues. On the basis of this theory, coupled with the collective findings from motion-analysis research, we sought to define the different pacing strategies employed by team sport players. Whole-match players adopt a ‘slow-positive’ pacing profile (gradual decline in total running intensity), which appears to be global across the different team sports. High-intensity movement also declines in a ‘slow-positive’ manner across most team sport matches. The duration of the exercise bout appears to be important for the selected exercise intensity, with the first introduction to a match as a substitute or interchange player resulting in a ‘one bout, all out’ strategy. In a limited interchange environment, a second introduction to the match results in a ‘second-bout reserve’ strategy; otherwise, the ‘one bout, all out’ strategy is likely to be adopted. These pacing profiles are proposed to reflect the presence of a central regulator that controls the movement intensity of the player to optimize performance, as well as avoiding the harmful failure of any physiological system. The presence of ‘temporary fatigue’ reflects this process, whereby exercise intensity is consciously modulated from within the framework of a global pacing schema.

Movement demands of elite rugby league players during Australian National Rugby League and European Super League matches.

PURPOSE This study compared the movement demands of players competing in matches from the elite Australian and European rugby league competitions. METHODS Global positioning system devices were used to measure 192 performances of forwards, adjustables, and outside backs during National Rugby League (NRL; n = 88) and European Super League (SL; n = 104) matches. Total and relative distances covered overall and at low (0-3.5 m/s), moderate (3.6-5 m/s), and high (>5 m/s) speeds were measured alongside changes in movement variables across the early, middle, and late phases of the season. RESULTS The relative distance covered in SL matches (95.8 ± 18.6 m/min) was significantly greater (P < .05) than in NRL matches (90.2 ± 8.3 m/min). Relative low-speed activity (70.3 ± 4.9 m/min vs 75.5 ± 18.9 m/min) and moderate-speed running (12.5 ± 3.3 m m/min vs 14.2 ± 3.8 m/min) were highest (P < .05) in the SL matches, and relative high-speed distance was greater (P < .05) during NRL matches (7.8 ± 2.1 m/min vs 6.1 ± 1.7 m/min). CONCLUSIONS NRL players have better maintenance of high-speed running between the first and second halves of matches and perform less low- and moderate-speed activity, indicating that the NRL provides a higher standard of rugby league competition than the SL.

The Effects of Exercise-Induced Muscle Damage on Agility and Sprint Running Performance

The purpose of this investigation was to assess the effects of exercise-induced muscle damage (EIMD) on agility and linear sprint running performance. Twelve healthy adults were randomly allocated to a treatment group (n = 7; age, 21 ± 1.2 years; height, 1.77 ± 0.11 m; body mass, 70.8 ± 8.2 kg) where they completed 100 plyo- metric jumps, or to a control group (n = 5; age, 24 ± 0.7 years; height, 1.77 ± 0.07 m; body mass, 69.2 ± 8.8 kg). Perceived muscle soreness, isokinetic peak torque of the knee extensors at 60 and 270 deg·s−1, sprint running time over 5 and 10 m, a timed agility test and ground contact time at the agility turn point were recorded at baseline and then 24, 48 and 168 hours following muscle-damaging exercise. Perceived muscle soreness was significantly increased (p 0.05). These findings indicate that agility and sprint performance is reduced following EIMD, and provides further evidence that performance of activities requiring rapid generation of force is impaired following muscle-damaging exercise.

The reliability and validity of short-distance sprint performance assessed on a nonmotorized treadmill

Highton, JM, Lamb, KL, Twist, C, and Nicholas, C. The reliability and validity of short-distance sprint performance assessed on a nonmotorized treadmill. J Strength Cond Res 26(2): 458–465, 2012—This study examined the interday and intraday reliabilities and validities of various sprint performance variables on a nonmotorized treadmill (NMT) over distances of 10, 20, and 30 m. After habituation, 12 male team-sport players performed 3 sprints on the NMT on 2 separate days and an assessment of overground running performance, separated by 24 hours. Measurements included sprint times, mean and peak sprint speeds, and step length and frequency. Data analysis revealed no significant mean differences (p > 0.05) between NMT variables recorded on the same day or between days. Ratio limits of agreement indicated that the best levels of agreement were in 20-m (1.02 ×/÷ 1.09) and 30-m (1.02 ×/÷ 1.07) sprint times, peak (1.00 ×/÷ 1.06) and mean (0.99 ×/÷ 1.07) running speed, and step length (0.99 ×/÷ 1.09) and frequency (1.01 ×/÷ 1.06). The poorest agreement was observed for time to peak running speed (1.10 ×/÷ 1.47). These reliability statements were reinforced by coefficients of variation being <5% for all the variables except time to peak running speed (11%). Significant differences (p < 0.05) were observed between NMT and overground sprint times across all distances, with times being lower (faster) by approximately 25–30% overground. The correlations between NMT and overground variables were generally modest (0.44–0.67), and optimal for time to cover 30 m on day 2. Our data support NMT ergometry as a reliable tool for most of the sprint performance variables measured and reveal that the fastest 30-m overground sprinters were likely to be identifiable via NMT ergometry.

Carbohydrate-protein coingestion improves multiple-sprint running performance

Abstract Acute carbohydrate-protein ingestion has been shown to improve steady-state endurance performance. This study compared the effects of carbohydrate and carbohydrate-protein ingestion on self-regulated simulated multiple-sprint sport performance. Nine participants completed two trials of a modified Loughborough Intermittent Shuttle Test involving 4 x 15 min blocks of regulated exercise followed by 2 x 15 min blocks of self-regulated exercise. Participants consumed 2.5 ml · kg−1 of an 8% carbohydrate (CHO trial) or 6% carbohydrate plus 2% whey protein beverage (CHO-P trial) every 15 minutes. Distance covered (4.2%) and maximal speed (6.1%) decreased (P < 0.05) in the final 15 min of exercise, and whilst not significant, carbohydrate-protein elicited a very likely moderate (2.5: 90% confidence limits; ±1.4%) and possibly small (1.9: ±3.3%) improvement in each variable, respectively. Average running speed declined in the final 15 min of the CHO trial only (P = 0.002), with protein providing a likely small improvement (2.7%: ±2.5%). No differences (P > 0.05) between beverages were observed in body mass or plasma volume change, urine volume, heart rate, gut fullness, rating of perceived exertion (RPE), blood glucose or serum insulin. Blood urea concentration increased in the CHO-P trial only (mean ± SD: 45.4 ± 9.9 c.f. 39.2 ± 11.4 g · dL−1, P = 0.003). These findings show carbohydrate-protein ingestion is likely to enhance multiple-sprint sport exercise performance above carbohydrate, potentially through altered central fatigue or increased protein oxidation.

Energy expenditure derived from micro-technology is not suitable for assessing internal load in collision-based activities

This aim of this study was to examine the validity of energy expenditure derived from microtechnology when measured during a repeated-effort rugby protocol. Sixteen male rugby players completed a repeated-effort protocol comprising 3 sets of 6 collisions during which movement activity and energy expenditure (EEGPS) were measured using microtechnology. In addition, energy expenditure was estimated from open-circuit spirometry (EEVO2). While related (r = .63, 90%CI .08-.89), there was a systematic underestimation of energy expenditure during the protocol (-5.94 ± 0.67 kcal/min) for EEGPS (7.2 ± 1.0 kcal/min) compared with EEVO2 (13.2 ± 2.3 kcal/min). High-speed-running distance (r = .50, 95%CI -.66 to .84) was related to EEVO2, while PlayerLoad was not (r = .37, 95%CI -.81 to .68). While metabolic power might provide a different measure of external load than other typically used microtechnology metrics (eg, high-speed running, PlayerLoad), it underestimates energy expenditure during intermittent team sports that involve collisions.

The Relationship between Match-Play Characteristics of Elite Rugby League and Indirect Markers of Muscle Damage

PURPOSE 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. METHODS 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. RESULTS 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. CONCLUSION Match duration, high-intensity running, and collisions were associated with variations in EIMD markers, suggesting that recovery is dependent on individual match demands.

A reliable testing battery for assessing physical qualities of elite academy rugby league players

Abstract Dobbin, N, Hunwicks, R, Highton, J, and Twist, C. A reliable testing battery for assessing physical qualities of elite academy rugby league players. J Strength Cond Res 32(11): 3232–3238, 2018—This study assessed the interday reliability of a testing battery for the assessment of physical qualities of rugby league players. Fifty players (age 17.1 ± 1.1 years; stature 181.3 ± 6.3 cm; and body mass 89.0 ± 11.6 kg) from 3 Super League academies participated in this study. Tests of countermovement jump performance, 10- and 20-m sprint performance, change of direction, medicine ball throw, and a modified Yo-Yo Intermittent Recovery Test Level 1 (prone Yo-Yo IR1) were completed on 3 separate occasions. Between-day intraclass correlation coefficient, typical error (TE), coefficient of variation, and the smallest worthwhile change (SWC) were calculated to determine the reliability and sensitivity of each measure. Individual tests (except medicine ball throw) were not systematically different between trials (p > 0.05), with an interday variability that was <10%. In all instances, the TE was larger than the calculated SWC change, although variability was less than that typically observed after a training intervention or specific training period (i.e. preseason). Using a magnitude-based inference approach, we present the required change for all performance tests to be 75% confident and the change is beneficial. This simple and time efficient testing battery is sufficiently reliable to detect previously observed changes in a range of physical qualities of rugby league players.