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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 [3] m·min−1 and 101 [3] m·min−1), low-speed distance (77 [3] m·min−1 and 79 [4] m·min−1), high-speed distance (25 [3] m·min−1 and 22 [4] m·min−1), PlayerLoad (10 [1] AU·min−1 and 10 [1] 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 [5]%HRmax and 84 [6]%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.

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Jamie Highton, Thomas Mullen, Jonathan Norris, Chelsea Oxendale and Craig Twist

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.