The physiological, perceptual and neuromuscular responses of team sport athletes to a running and cycling high intensity interval training session.

PURPOSE: The acute physiological, perceptual and neuromuscular responses to volume-matched running and cycling high intensity interval training (HIIT) were studied in team sport athletes. METHODS: In a randomized cross-over design, 11 male team sport players completed 3 × 6 min (with 5 min between sets) repeated efforts of 15 s exercising at 120% speed (s[Formula: see text]O2max) or power (p[Formula: see text]O2max) at [Formula: see text]O2max followed by 15 s passive recovery on a treadmill or cycle ergometer, respectively. RESULTS: Absolute mean [Formula: see text]O2 (ES [95% CI] = 1.46 [0.47-2.34], p < 0.001) and heart rate (ES [95% CI] = 1.53 [0.53-2.41], p = 0.001) were higher in running than cycling HIIT. Total time at > 90% [Formula: see text]O2max during the HIIT was higher for running compared to cycling (ES [95% CI] = 1.21 [0.26-2.07], p = 0.015). Overall differential RPE (dRPE) (ES [95% CI] = 0.55 [- 0.32-1.38], p = 0.094) and legs dRPE (ES [95% CI] = - 0.65 [- 1.48-0.23], p = 0.111) were similar, whereas breathing dRPE (ES [95% CI] = 1.01 [0.08-1.85], p = 0.012) was higher for running. Maximal isometric knee extension force was unchanged after running (ES [95% CI] = - 0.04 [- 0.80-0.8], p = 0.726) compared to a moderate reduction after cycling (ES [95% CI] = - 1.17 [- 2.02-0.22], p = 0.001). CONCLUSION: Cycling HIIT in team sport athletes is unlikely to meet the requirements for improving run-specific metabolic adaptation but might offer a greater lower limb neuromuscular load.

The Effects of an Acute Dose of New Zealand Blackcurrant Extract on 5-km Running Performance.

This study investigated the effects of an acute dose (900 mg) of New Zealand Blackcurrant (NZBC) extract on 5-km running performance, alongside associated physiological and metabolic responses. Sixteen trained male runners (age 26 ± 5 years, stature 173.4 ± 7.3 cm, body mass 73.7 ± 6.9 kg, maximal oxygen consumption [V˙O2max] 55.4 ± 6.1 ml·kg-1·min-1) ingested either capsules containing NZBC extract (3 × 300 mg CurraNZ, 315 mg anthocyanins) or a matched placebo (3 × 300 mg gluten-free flour) 2 hr before exercise in a double-blind, randomized, crossover design. Performance time, physiological, and metabolic responses were assessed in a 5-km time trial, preceded by 10-min exercise at the lactate threshold on a treadmill. NZBC extract did not alter the physiological or metabolic responses to exercise at the lactate threshold (oxygen uptake, respiratory exchange ratio, minute ventilation, carbohydrate oxidation, fat oxidation, heart rate, blood lactate, or rating of perceived exertion, p > .05). The 5-km time trial was completed in a faster time in the NZBC extract condition compared with placebo (NZBC: 1,308.96 ± 122.36 s, placebo: 1,346.33 ± 124.44, p = .001, d = -0.23, confidence interval range = [-0.46, 0.00 s]). No differences in physiological or metabolic responses were apparent between conditions for the 5-km time trial (p > .05). Ingesting 900 mg of NZBC extract as an acute dose improves performance in trained male runners without altering physiological or metabolic responses to exercise. Further research is needed to assess a wider range of possible mechanisms (e.g., cardiovascular function, metabolite profiles) to advance insight into improved performance following supplementation.

Passive Heat Maintenance After an Initial Warm-up Improves High-Intensity Activity During an Interchange Rugby League Movement Simulation Protocol.

ABSTRACT: Fairbank, M, Highton, J, Twist, C. Passive heat maintenance after an initial warm-up improves high-intensity activity during an interchange rugby league movement simulation protocol. J Strength Cond Res 35(7): 1981-1986, 2021-This study examined using passive heat maintenance (PHM) to maintain core temperature after a warm-up and its effect on simulated first half running performance in rugby players. Thirteen male rugby players completed this randomized crossover study. Tympanic temperature was taken before a warm-up and then after a further 15 minutes of passive recovery either with (PHM) or without (CON) a PHM garment. Subjects then completed 23 minutes of the rugby league movement simulation protocol (RLMSP-i). Differences in tympanic temperature were unclear between CON and PHM before (35.7 ± 1.3 cf. 36.0 ± 1.1° C; effect size [ES] = 0.20) and during exercise (34.5 ± 0.1 cf. 35.2 ± 0.1° C; ES = 0.26-0.35). High-intensity running (ES = 0.27) and peak sprint speed were higher (ES = 0.46-0.56) during the PHM compared with the CON trial. Time spent above 20 W·kg-1 also increased in the first quartile of the PHM compared with the CON trial (ES = 0.18). All other between trial comparisons of performance were unclear. HRmean (ES = 0.38) was higher in PHM compared with CON, while differences in RPEmean (ES = -0.19) were unclear. There are small to large increases in high-intensity activity performed during a playing bout when rugby players wear a PHM garment after a warm-up. Rugby players should consider PHM during extended periods between a warm-up and starting a match.

Concurrent Validity of a Rugby-Specific Yo-Yo Intermittent Recovery Test (Level 1) for Assessing Match-Related Running Performance.

ABSTRACT: Dobbin, N, Highton, J, Moss, SL, Hunwicks, R, and Twist, C. Concurrent validity of a rugby-specific Yo-Yo intermittent recovery test (level 1) for assessing match-related running performance. J Strength Cond Res 35(1): 176-182, 2021-This study investigated the concurrent validity of a rugby-specific high-intensity intermittent running test against the internal, external, and perceptual responses to simulated match play. Thirty-six rugby league players (age 18.5 ± 1.8 years; stature 181.4 ± 7.6 cm; body mass 83.5 ± 9.8 kg) completed the prone Yo-Yo Intermittent Recovery Test (Yo-Yo IR1), of which 16 also completed the Yo-Yo IR1, and 2 × âˆ¼20 minute bouts of a simulated match play (rugby league match simulation protocol for interchange players [RLMSP-i]). Most likely reductions in relative total, low-speed and high-speed distance, mean speed, and time above 20 W·kg-1 (high metabolic power [HMP]) were observed between bouts of the RLMSP-i. Likewise, rating of perceived exertion (RPE) and percentage of peak heart rate (%HRpeak) were very likely and likely higher during the second bout. Pearson's correlations revealed a large relationship for the change in relative distance (r = 0.57-0.61) between bouts with both Yo-Yo IR1 tests. The prone Yo-Yo IR1 was more strongly related to the RLMSP-i for change in repeated sprint speed (r = 0.78 cf. 0.56), mean speed (r = 0.64 cf. 0.36), HMP (r = 0.48 cf. 0.25), fatigue index (r = 0.71 cf. 0.63), %HRpeak (r = -0.56 cf. -0.35), RPEbout1 (r = -0.44 cf. -0.14), and RPEbout2 (r = -0.68 cf. -0.41) than the Yo-Yo IR1, but not for blood lactate concentration (r = -0.20 to -0.28 cf. -0.35 to -0.49). The relationships between prone Yo-Yo IR1 distance and measures of load during the RLMSP-i suggest that it possesses concurrent validity and is more strongly associated with measures of training or match load than the Yo-Yo IR1 using rugby league players.

Stochastic ordering of simulated rugby match activity produces reliable movements and associated measures of subjective task load, cognitive and neuromuscular function.

The study assesses the test-retest reliability of movement and physiological measures during a simulated rugby match that employed activities performed in a stochastic order. Twenty male rugby players (21.4 ± 2.1 y) completed two trials of a 2 × 23 min rugby movement simulation protocol during which the order of events was performed in a stochastic order, with 7-10 days between trials. Movement characteristics, heart rate (HR), RPE, maximum voluntary contraction (MVC), voluntary activation (VA%) of the quadriceps, Stroop test and subjective task load rating (NASA-TLX) were measured. The most reliable measures of external load was relative distance (typical error [TE] and CV% = 1.5-1.6 m min-1 and 1.4-1.5%, respectively), with all other movement characteristics possessing a CV% <5%. The most reliable measure of internal load, neuromuscular function and perceptual measures were for %HRmax (TE and CV% = 1.4-1.7% and 1.4-2.1%, respectively), MVC before (TE and CV% = 10.8-14.8 N·m and 3.8-4.6%, respectively), and average RPE (TE and CV% = 0.5-0.8 AU and 3.6-5.5%, respectively). The Stroop test, NASA-TLX and blood lactate produced the least reliable measures (CV% >5%). Future studies can confidently examine changes in several perceptual, neuromuscular, physiological and movement measures related to rugby activity using stochastic movements.

Carbohydrate and Caffeine Improves High-Intensity Running of Elite Rugby League Interchange Players During Simulated Match Play.

Clarke, JS, Highton, J, Close, GL, and Twist, C. Carbohydrate and caffeine improves high-intensity running of elite rugby league interchange players during simulated match play. J Strength Cond Res 33(5): 1320-1327, 2019-The study examined the effects of carbohydrate and caffeine ingestion on simulated rugby league interchange performance. Eight male elite rugby league forwards completed 2 trials of a rugby league simulation protocol for interchange players 7 days apart in a randomized crossover design, ingesting either carbohydrate (CHO; 40 g·h) or carbohydrate and caffeine (CHO-C) (40 g·h + 3 mg·kg) drink. Movement characteristics, heart rate, ratings of perceived exertion (RPE), and countermovement jump (CMJ) height were measured during the protocol. CHO-C resulted in likely to very likely higher mean running speeds (effect size [ES] 0.43-0.75), distance in high-intensity running (ES 0.41-0.64), and mean sprint speeds (ES 0.39-1.04) compared with CHO. Heart rate was possibly to very likely higher (ES 0.32-0.74), and RPE was likely to very likely lower (ES -0.53 to 0.86) with CHO-C. There was a likely trivial to possibly higher CMJ in CHO-C compared with CHO (ES 0.07-0.25). The coingestion of carbohydrate with caffeine has an ergogenic effect to reduce the sense of effort and increase high-intensity running capability that might be used to enhance interchange running performance in elite rugby league players.

Transient Fatigue is Not Influenced by Ball-In-Play Time During Elite Rugby League Matches.

Waldron, M, Thomson, E, Highton, J, and Twist, C. Transient fatigue is not influenced by ball-in-play time during elite rugby league matches. J Strength Cond Res 33(1): 146-151, 2019-The capacity to sustain high-speed running is important for rugby league players. Transient fatigue, described as a reduction in high-speed running in the 5 minutes after a peak 5-minute period, is a phenomenon observed during rugby league matches. This concept has recently been questioned based on the proposed confounding influence of ball-in-play time during these periods. Therefore, this study examined the changes in high-speed running (>14 km·h) of elite rugby league players, and ball-in-play time, during the peak, subsequent, and mean 5-minute periods of 5 competitive matches using 5-Hz Global Positioning System devices. The suitability of ball-in-play time as a covariate was also evaluated. The high-speed running and ball-in-play time was different between peak (26.7 ± 5.5 m·min and 177 ± 37 seconds) and subsequent (12.1 ± 6.2 m·min and 147 ± 37 seconds) 5-minute periods (p ≤ 0.05; most likely ↓). However, there was no relationship (r = 0.01 to -0.13; p > 0.05) between ball-in-play time and high-speed running, and ball-in-play time was not independent of the match period. This study has reaffirmed the presence of transient fatigue during elite rugby league matches but questioned the influence of ball-in-play time as a confounding factor. These observations have implications for the design of appropriate training practices and informing tactical strategies used by coaches. Most importantly, any practitioner wishing to measure transient fatigue could follow a similar statistical approach taken herein and based on the current findings would not need to account for ball-in-play time as a confounding variable.

Beetroot supplementation improves the physiological responses to incline walking.

PURPOSE: We investigated the effects of an acute 24-h nitrate-rich beetroot juice supplement (BR) on the energy cost, exercise efficiency and blood pressure responses to intermittent walking at different gradients. METHODS: In a double-blind, cross-over design, eight participants were provided with a total of 350 ml of nitrate-rich (~ 20.5 mmol nitrate) BR or placebo (PLA) across 24 h before completing intermittent walking at 3 km/h on treadmill at gradients of 1, 5, 10, 15 and 20%. RESULTS: Resting mean arterial pressure (MAP) was ~ 4.1% lower after BR (93 vs. 89 mmHg; P = 0.001), as well as during exercise (102 vs. 99 mmHg; P = 0.011) and recovery (97 vs. 94 mmHg; P = 0.001). Exercising (1227 vs. 1129 ml/min P < 0.001) and end-stage (1404 vs. 1249 ml/min; P = 0.002) oxygen uptake ([Formula: see text]O2) was lower in BR compared to PLA, which was accompanied by an average reduction in phase II [Formula: see text]O2 amplitude (1067 vs. 940 ml/min; P = 0.025). Similarly, recovery [Formula: see text]O2 (509 vs. 458 ml/min; P = 0.001) was lower in BR. Whole blood potassium concentration increased from pre-post exercise in PLA (4.1 ± 0.3 vs. 4.5 ± 0.3 mmol/L; P = 0.013) but not BR (4.1 ± 0.31 vs. 4.3 ± 0.2 mmol/L; P = 0.188). CONCLUSIONS: Energy cost of exercise, recovery of [Formula: see text]O2, MAP and blood markers were ameliorated after BR. Previously-reported mechanisms explain these findings, which are more noticeable during less-efficient walking at steep gradients (15-20%). These findings have practical implications for hill-walkers.

A Reliable Testing Battery for Assessing Physical Qualities of Elite Academy Rugby League Players.

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.

Glutamine supplementation reduces markers of intestinal permeability during running in the heat in a dose-dependent manner.

PURPOSE: To examine the dose-response effects of acute glutamine supplementation on markers of gastrointestinal (GI) permeability, damage and, secondary, subjective symptoms of GI discomfort in response to running in the heat. METHODS: Ten recreationally active males completed a total of four exercise trials; a placebo trial and three glutamine trials at 0.25, 0.5 and 0.9 g kg-1 of fat-free mass (FFM) consumed 2 h before exercise. Each exercise trial consisted of a 60-min treadmill run at 70% of [Formula: see text] in an environmental chamber set at 30 °C. GI permeability was measured using ratio of lactulose to rhamnose (L:R) in serum. Plasma glutamine and intestinal fatty acid binding protein (I-FABP) concentrations were determined pre and post exercise. Subjective GI symptoms were assessed 45 min and 24 h post-exercise. RESULTS: Relative to placebo, L:R was likely lower following 0.25 g kg-1 (mean difference: - 0.023; ± 0.021) and 0.5 g kg-1 (- 0.019; ± 0.019) and very likely following 0.9 g kg- 1 (- 0.034; ± 0.024). GI symptoms were typically low and there was no effect of supplementation. DISCUSSION: Acute oral glutamine consumption attenuates GI permeability relative to placebo even at lower doses of 0.25 g kg-1, although larger doses may be more effective. It remains unclear if this will lead to reductions in GI symptoms. Athletes competing in the heat may, therefore, benefit from acute glutamine supplementation prior to exercise in order to maintain gastrointestinal integrity.

Validity of a Jump Mat for assessing Countermovement Jump Performance in Elite Rugby Players.

This study determined the validity of the Just Jump System® (JJS) for measuring flight time, jump height and peak power output (PPO) in elite rugby league players. 37 elite rugby league players performed 6 countermovement jumps (CMJ; 3 with and 3 without arms) on a jump mat and force platform. A sub-sample (n=28) was used to cross-validate the equations for flight time, jump height and PPO. The JJS systematically overestimated flight time and jump height compared to the force platform (P<0.05), but demonstrated strong associations for flight time (with R2=0.938; without R2=0.972) and jump height (with R2=0.945; without R2=0.987). Our equations revealed no systematic difference between corrected and force platform scores and an improved the agreement for flight time (Ratio limits of agreement: with 1.00 vs. 1.36; without 1.00 vs. 1.16) and jump height (with 1.01 vs. 1.34; without 1.01 vs. 1.15), meaning that our equations can be used to correct JJS scores for elite rugby players. While our equation improved the estimation of PPO (with 1.02; without 1.01) compared to existing equations (Harman: 1.20; Sayers: 1.04), this only accounted for 64 and 69% of PPO.

The effects of physical contact type on the internal and external demands during a rugby league match simulation protocol.

The aim of this study was to investigate how the type of contact influences physiological, perceptual and locomotive load during a simulated rugby league match. Eleven male university rugby league players performed two trials of the rugby league movement simulation protocol for interchange forwards with a traditional soft tackle bag and a weighted tackle sled to replicate contact demands. The interchange forward-specific simulation was chosen given the contact frequency is higher for this group of players compared to whole match players. Locomotive rate, sprint speed, tackle intensity, heart rate (HR) and rating of perceived exertion were analysed during the first and second bouts that replicated two ~23 min on-field passages. Countermovement jump (CMJ) was measured before and immediately after each trial. More time was spent in heart rate zone between 91 and 100% HRpeak during the first (effect size ± 90% confidence interval: 0.44 ± 0.49) and second bouts (0.44 ± 0.43), and larger (0.6 ± 0.69) decrements in CMJ performance were observed during the sled trial (5.9, s = 4.9%) compared to the bag trial (2.6, s = 5.4%). Changing the type of contact during the match simulation subtly altered both the internal and external loads on participants. Using a standard tackle bag results in faster sprint speed to contact, but lower overall high-intensity running. Conversely, a heavier tackle object increases the internal load and results in greater lower limb neuromuscular fatigue as reflected by the decrease in CMJ performance.

Movement and physiological demands of international and regional men's touch Rugby matches.

This study compared the internal and external match demands imposed on international and regional standard male touch rugby players. The study adopted a cohort design with independent groups. Twelve international players (mean age, 27.8 ± 6.2 years; body mass, 72.8 ± 3.7 kg; stature, 174.5 ± 5.4 cm) and 9 regional players (mean age, 25.5 ± 5.5 years; body mass 74.2 ± 7 kg; stature 174.1 ± 7 cm) were analyzed during 9 competitive matches from the 2013 season. Movement demands were measured using a 5-Hz global positioning system, alongside heart rate (HR) and session rating of perceived exertion (s-RPE) to quantify internal load. Total distance covered by international players was lower than regional players (2265.8 ± 562.3 cf. 2970 ± 558.9 m; p ≤ 0.05). However, international players had greater relative distance (137.1 ± 13.6 cf. 126.2 ± 17.2 m·min) due to shorter playing times per match (p ≤ 0.05). Absolute high-speed running (>14 km·h) was not different between groups (p > 0.05), but relative high-speed running (39.3 ± 12.0 cf. 26.0 ± 13.6 m·min) was higher for international players. Regional players performed more absolute low-speed activity (≤14 km·h) than international players (p ≤ 0.05), whereas relative low-speed activity was not different between groups (p > 0.05). Very high-speed running (>20 km·h) distance, bout number and frequency, peak, and average speed were all greater in international players (p ≤ 0.05). Higher average HR, summated HR, and s-RPE (p ≤ 0.05) indicated higher internal loads during matches for regional players. These data indicate that performance in men's touch rugby is characterized by more relative high-speed running and better repeated sprint capacities in higher standard players.

Carbohydrate-protein coingestion improves multiple-sprint running performance.

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.

Can Player Tracking Devices Monitor Changes in Internal Response During Multidirectional Running?

Purpose: We examined the movement, physiological and muscle function responses to running with and without (i.e. linear) multiple directional changes to understand which measures of external demands better reflected changes in the internal response. Methods: Twelve team sport athletes completed a linear and multidirectional running trial during which movement characteristics, oxygen consumption (V˙O2), blood lactate (B[La]) and heart rate (HR) were measured. Isometric peak torque of knee extensors and flexors was also assessed before and after each trial. Results: High speed running distance was higher during the linear trial (p < 0.001), whereas time at high metabolic power (p = 0.046), number of accelerations (p < 0.001), summated HR (p = 0.003) and B[La] (p = 0.002) were higher during the multidirectional trial. Integrated external to internal ratios of high-speed running: summated HR and high-speed running: total V˙O2 were different between multidirectional and linear trials (p ≤ 0.001). Conversely, high metabolic power: summated HR and high metabolic power: total V˙O2 were similar (p ≥ 0.246). Small decrements in knee flexor (p = 0.003) and extensor torque (p = 0.004) were observed after both trials. Conclusion: Time at high metabolic power better reflects the increased internal response during running with more directional changes than high speed running.

Individual and situational factors affecting the movement characteristics and internal responses to Touch match-play during an international tournament.

PURPOSE: To examine the influence of individual and situational factors on the movement characteristics and internal responses of players to an international Touch tournament. METHODS: Using 47 International Touch players (25 men and 22 women), the associations between the movement characteristics and internal responses with individual (sprint, glycolytic test, Yo-Yo intermittent recovery test level 1 [Yo-Yo IR1], jump performance and well-being) and situational (sex, squad, position, competition day, points scored/conceded, result, and opposition rank) factors were examined using linear mixed modelling. RESULTS: Yo-Yo IR1 distance was associated with all movement characteristics and internal responses (r = -0.29 to 0.37), whilst sprint and glycolytic times only influenced mean heart rate (HRmean) (r = 0.15) and high-speed distance (r = 0.10), respectively. Sex influenced high-speed distance (r = -0.41), whilst squad was associated with playing time and HRmean (r = -0.10-0.33). Other associations included: playing position with all movement characteristics (r = -0.67-0.81); points conceded with relative distance (r = -0.14); winning with high metabolic power and session RPE (r = -0.07-0.09), and opposition rank with HRmean and RPE (r = 0.11-0.35). CONCLUSIONS: Individual and situational factors can influence the movement characteristics and internal responses to Touch and should be considered when developing the characteristics of players and interpreting responses to match-play.

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

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.

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

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.

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

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.

The Physiological and Perceptual Effects of Stochastic Simulated Rugby League Match Play.

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.