Rich D. Johnston

Physiological responses to an intensified period of rugby league competition.

Abstract Johnston, RD, Gibson, NV, Twist, C, Gabbett, TJ, MacNay, SA, and MacFarlane, NG. Physiological responses to an intensified period of rugby league competition. J Strength Cond Res 27(3): 643–654, 2013—This study investigated the physiological responses to an intensified period of rugby league competition and the subsequent impact on match performance. The participants were 7 rugby league players competing in an international student tournament. The tournament involved three 80-minute games over a 5-day period, with 48 hours between each match. Baseline measures of upper and lower body neuromuscular functions via a plyometric press-up (PP) and countermovement jump (CMJ), respectively (peak power and peak force were measured), blood creatine kinase (CK), and perceptions of well-being were assessed with a questionnaire. These measures were repeated every morning of the competition; neuromuscular fatigue and CK were additionally assessed within 2 hours after the cessation of each game. During each match, player movements were recorded via global positioning system units. There were meaningful reductions in upper (effect size [ES] = −0.55) and lower body (ES = −0.73) neuromuscular functions, and perceptual well-being (ES = −1.56) and increases in blood CK (ES = 2.32) after game 1. These changes increased in magnitude as the competition progressed. There were large reductions in the relative distance covered in high-speed running (ES = −1.49) and maximal accelerations (ES = −0.85) during game 3. Additionally, moderate reductions in the percentage of successful tackles completed were observed during game 3 (ES = −0.59). Collectively, these results demonstrate that during an intensified period of rugby league competition, characterized by only 48 hours between matches, fatigue will accumulate. This cumulative fatigue may compromise high-intensity match activities such as high-speed running, accelerations, and tackling. Furthermore, CMJs and PPs appear to be sensitive measures for monitoring neuromuscular function in rugby league players.

Repeated-sprint and effort ability in rugby league players.

Johnston, RD and Gabbett, TJ. Repeated-sprint and effort ability in rugby league players. J Strength Cond Res 25(10): 2789–2795, 2011—The aim of this study was to (a) investigate the influence of tackling on repeated-sprint performance; (b) determine whether repeated-sprint ability (RSA) and repeated-effort ability (REA) are 2 distinct qualities; and (c) assess the test–retest reliability of repeated-sprint and repeated-effort tests in rugby league. Twelve rugby league players performed a repeated-sprint (12 × 20-m sprints performed on a 20-second cycle) and a repeated-effort (12 × 20-m sprints with intermittent tackling, performed on a 20-second cycle) test 7 days apart. The test–retest reliability of these tests was also established. Heart rate and rating of perceived exertion were recorded throughout the tests. There was a significantly greater (p ≤ 0.05) and large effect size (ES) differences for total sprint time (ES = 1.19), average heart rate (ES = 1.64), peak heart rate (ES = 1.35), and perceived exertion (ES = 3.39) for the repeated-effort test compared with the repeated-sprint test. A large difference (ES = 1.02, p = 0.06) was detected for percentage decrement between the 2 tests. No significant relationship was found between the repeated-sprint and repeated-effort tests for any of the dependent variables. Both tests proved reliable, with total sprint time being the most reliable method of assessing performance. This study demonstrates that the addition of tackling significantly increases the physiological response to repeated-sprint exercise and reduces repeated-sprint performance in rugby league players. Furthermore, RSA and REA appear to be 2 distinct qualities that can be reliably assessed with total time being the most reliable measure of performance.

Influence of physical qualities on post-match fatigue in rugby league players.

OBJECTIVES This study examined the influence of physical qualities on markers of fatigue and muscle damage following rugby league match-play. DESIGN Between subjects design. METHODS Twenty-one male youth rugby league players (age 19.2 ± 0.7 years; height 180.7 ± 5.6 cm; body mass 89.9 ± 10.0 kg) participated in the study. Yo-Yo intermittent recovery test (level 1), 3 repetition maximum back squat and bench press were assessed prior to 2 competitive fixtures. Neuromuscular fatigue (countermovement jump [CMJ] and plyometric push-up [PP]), and blood creatine kinase (CK) were assessed before and after match-play. During match-play, movements were recorded using microtechnology. Players were divided into high- and low-groups based on physical qualities. RESULTS High Yo-Yo and squat performance resulted in greater loads during match-play (p<0.05). There were larger reductions in CMJ power in the low Yo-Yo group at both 24 (ES=-1.83), and 48 h post-match (ES=-1.33). Despite greater internal and external match loads, changes in CMJ power were similar between squat groups. There were larger increases in blood CK in the low Yo-Yo group at 24 (73% vs. 176%; ES=1.50) and 48 h post-match (28% vs. 80%; ES=1.22). Despite greater contact loads, the high squat group exhibited smaller changes in blood CK post-match (ES=0.25-0.39). CONCLUSIONS Post-match fatigue is lower in players with well-developed high-intensity running ability, and lower body strength, despite these players having greater internal and external match loads.

Influence of physical contact on neuromuscular fatigue and markers of muscle damage following small-sided games.

OBJECTIVES Physical contact is frequent in rugby league competition and is thought to be a major contributor to the fatigue and creatine kinase (CK) response, although direct evidence is lacking. The aim of this study was to investigate the influence that physical contact had on the fatigue and CK response to small-sided games. DESIGN Cross-over, counter-balanced study. METHODS Twenty-three junior elite rugby league players were divided into two groups. Group one played a contact game on day 1 before playing a non-contact game 72 h later; group two played the games in reverse order. The rules were identical for each game, with the only difference being a 10s contact bout every 50s during the contact game. Upper and lower body neuromuscular fatigue and blood concentrations of CK were assessed immediately before, immediately after, and 12 and 24h after the games. During each game, players wore global positioning system units to provide information on movements. RESULTS CK increased after both games, peaking immediately following the non-contact game; CK was still rising 24h following the contact game. The difference between the two conditions was practically meaningful at this point (likelihood=likely, 82%; ES=0.86). There were moderate to large reductions in upper body power following the contact game (ES=-0.74 to -1.86), and no reductions following the non-contact game. CONCLUSIONS This study indicates that large increases in blood CK and upper body fatigue result from physical contact. Training sessions involving physical contact should be performed well in advance of scheduled games.

Influence of physical contact on pacing strategies during game-based activities

PURPOSE Repeated sprinting incorporating tackles leads to greater reductions in sprint performance than repeated sprinting alone. However, the influence of physical contact on the running demands of game-based activities is unknown. The aim of this study was to determine whether the addition of physical contact altered pacing strategies during game-based activities. METHODS Twenty-three elite youth rugby league players were divided into 2 groups. Group 1 played the contact game on day 1 while group 2 played the noncontact game; 72 h later they played the alternate game. Each game consisted of offside touch on a 30 × 70-m field, played over two 8-min halves. Rules were identical between games except the contact game included a 10-s wrestle bout every 50 s. Microtechnology devices were used to analyze player movements. RESULTS There were greater average reductions during the contact game for distance (25%, 38 m/min, vs 10%, 20 m/min; effect size [ES] = 1.78 ± 1.02) and low-speed distance (21%, 24 m/min, vs 0%, 2 m/s; ES = 1.38 ± 1.02) compared with the noncontact game. There were similar reductions in high-speed running (41%, 18 m/min, vs 45%, 15 m/min; ES = 0.15 ± 0.95). CONCLUSIONS The addition of contact to game-based activities causes players to reduce low-speed activity in an attempt to maintain high-intensity activities. Despite this, players were unable to maintain high-speed running while performing contact efforts. Improving a players ability to perform contact efforts while maintaining running performance should be a focus in rugby league training.

Muscular Strength and Power Correlates of Tackling Ability in Semiprofessional Rugby League Players

Abstract Speranza, MJA, Gabbett, TJ, Johnston, RD, and Sheppard, JM. Muscular strength and power correlates of tackling ability in semiprofessional rugby league players. J Strength Cond Res 29(8): 2071–2078, 2015—This study investigated the relationship between muscular strength and power and tackling ability in semiprofessional rugby league players. Thirty-six semiprofessional (mean ± SD age, 23.1 ± 3.6 years) rugby league players, from 3 distinct playing divisions (first grade, second grade, and under 20s), underwent tests of upper-body strength (3 repetition maximum [RM] bench press), lower-body strength (3RM squat), upper-body power (plyometric push-up [PPU]), and lower-body power (countermovement jump). Muscular strength relative to body mass was also calculated. Tackling ability of the players was tested using video analysis of a standardized one-on-one tackling drill. For all players, the strongest correlates of tackling ability were squat (r = 0.67), bench press (r = 0.58), relative squat (r = 0.41), and PPU (r = 0.56). The strongest correlates of tackling ability in first grade players were squat (r = 0.72), bench press (r = 0.72), relative squat (r = 0.86), and PPU (r = 0.70). For second grade players, only relative squat (r = 0.60) and PPU (r = 0.67) were associated with tackling ability. The strongest correlates of tackling ability in under 20s players were squat (r = 0.77), bench press (r = 0.70), and PPU (r = 0.65). The findings of this study demonstrate that muscular strength and upper-body power contribute to tackling ability in semiprofessional rugby league players. Therefore, as long as the technical aspects of tackling technique are adequately coached and practiced, then enhancements in muscular strength and power may serve as foundational components to underpin improvement in tackling ability.

Wearable microtechnology can accurately identify collision events during professional rugby league match-play

OBJECTIVES Collision frequency during rugby league matches is associated with team success, greater and longer lasting fatigue and increased injury risk. This study researched the sensitivity and specificity of microtechnology to count collision events during rugby league matches. DESIGN Diagnostic accuracy study. METHODS While wearing a microtechnology device (Catapult, S5), eight professional rugby league players were subjected to a total of 380 collision events during matches. Video footage of each match was synchronised with microtechnology data. The occurrence of each collision event was coded in comparison with whether that event was or was not detected by microtechnology. RESULTS Microtechnology detected 371 true-positive collision events (sensitivity=97.6±1.5%). When low-intensity (<1 PlayerLoad AU), short duration (<1s) events were excluded from the analysis, specificity was 91.7±2.5%, accuracy was 92.7±1.3%, positive likelihood ratio was 11.4×/÷1.4 and the typical error of estimate was 7.8%×/÷1.9 (d=0.29×/÷1.9, small). Microtechnology collisions were strongly and positively correlated with video coded collision events (r=0.96). The ability of microtechnology to detect collision events improved as the intensity and duration of the collision increased. CONCLUSIONS Microtechnology can identify 97.6% of collision events during rugby league match-play. The typical error associated with measuring contact events can be reduced to 7.8%, with accuracy (92.7%) and specificity (91.7%) improving, when low-intensity (<1 PlayerLoad AU) and short duration (<1s) collision reports are excluded. This provides practitioners with a measurement of contact workload during professional rugby league matches.

Effect of Strength and Power Training on Tackling Ability in Semiprofessional Rugby League Players.

Abstract Speranza, MJA, Gabbett, TJ, Johnston, RD, and Sheppard, JM. Effect of strength and power training on tackling ability in semiprofessional rugby league players. J Strength Cond Res 30(2): 336–343, 2016—This study examined the influence of a strength and power program on tackling ability in rugby league players. Twenty-four semiprofessional rugby league players (mean ± SD age, 23.4 ± 3.1 years) underwent tests of upper-body strength (3 repetition maximum [RM] bench press), lower-body strength (3RM squat), upper-body power (plyometric push-up), and lower-body power (countermovement jump [CMJ]). Muscular strength relative to body mass was also calculated. Tackling ability of the players was assessed using video analysis of a standardized one-on-one tackling drill. The players then underwent 8 weeks of strength and power training as part of their preseason training before being retested. Training resulted in significant (p ⩽ 0.01) improvements in absolute and relative measures of squat, bench press, CMJ peak power, and plyometric push-up peak power. The strongest correlates of change in tackling ability were changes in 3RM squat (r = 0.60; p < 0.01) and squat relative to body mass (r = 0.54; p < 0.01). The players with the greatest improvements in 3RM squat and squat relative to body mass (i.e., responders) had significantly greater improvements in tackling ability than nonresponding players (p = 0.04; effect size [ES] ≥ 0.85). A small, nonsignificant difference (p = 0.20; ES = 0.56) in tackling ability was found between responders and nonresponders for lower-body power. The findings of this study demonstrate that the enhancement of lower-body muscular strength, and to a lesser extent muscular power, contribute to improvements in tackling ability in semiprofessional rugby league players.

Relationship Between Training Load, Fitness, and Injury Over an Australian Rules Football Preseason

Abstract Harrison, PW and Johnston, RD. Relationship between training load, fitness, and injury over an Australian rules football preseason. J Strength Cond Res 31(10): 2686–2693, 2017—Recent research identifies that certain training load (TL) patterns increase the injury risk to athletes. However, physical fitness must also be considered to establish optimal TL patterns. The aim of this study was to identify TL patterns optimal for injury and aerobic fitness by exploring the TL-injury and TL-fitness relationship concurrently over an Australian rules football (ARF) preseason. Individual TL, aerobic fitness, and injury data were collected over a 14-week preseason in 60 subelite ARF players (age = 21.3 ± 2.9 years). Individual TL, assessed through session rating of perceived exertion (sRPE), was compared with noncontact, lower limb soft tissue injury to examine the TL-injury relationship. A 2-km time trial was used as the measure of aerobic fitness to examine the optimal TL for aerobic fitness improvement. Aerobic fitness improved by 4.10 ± 2.20% (range = −7.35–19.05%) over the preseason. Training load between 1,600 and 2,000 AU per week was associated with the greatest aerobic fitness improvement (effect size [ES] = 0.47–1.01). Players with preseason TL <1,250 AU per week had the highest injury rate (ES = 0.52–0.62). Large 2-week TL (>4,000 AU, odds ratio [OR] = 2.80) and spikes in weekly TL (15–49%, OR = 3.76) significantly increased injury risk the following week. Performing small amounts of training seems to be the most detrimental to changes in aerobic fitness and injury rate. High TL is not responsible for injuries and is required to maximize improvements in aerobic fitness. However, TL exceeding 2,000 AU over several weeks may attenuate aerobic fitness improvements and increase injury risk. In addition, large increments in weekly TL increase injury risk.

Influence of number of contact efforts on running performance during game-based activities

PURPOSE To determine the influence the number of contact efforts during a single bout has on running intensity during game-based activities and assess relationships between physical qualities and distances covered in each game. METHODS Eighteen semiprofessional rugby league players (age 23.6 ± 2.8 y) competed in 3 off-side small-sided games (2 × 10-min halves) with a contact bout performed every 2 min. The rules of each game were identical except for the number of contact efforts performed in each bout. Players performed 1, 2, or 3 × 5-s wrestles in the single-, double-, and triple-contact game, respectively. The movement demands (including distance covered and intensity of exercise) in each game were monitored using global positioning system units. Bench-press and back-squat 1-repetition maximum and the 30-15 Intermittent Fitness Test (30-15IFT) assessed muscle strength and high-intensity-running ability, respectively. RESULTS There was little change in distance covered during the single-contact game (ES = -0.16 to -0.61), whereas there were larger reductions in the double- (ES = -0.52 to -0.81) and triple-contact (ES = -0.50 to -1.15) games. Significant relationships (P < .05) were observed between 30-15IFT and high-speed running during the single- (r = .72) and double- (r = .75), but not triple-contact (r = .20) game. CONCLUSIONS There is little change in running intensity when only single contacts are performed each bout; however, when multiple contacts are performed, greater reductions in running intensity result. In addition, high-intensity-running ability is only associated with running performance when contact demands are low.