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.

Locomotor characteristics of the women's inaugural super league competition and the rugby league world cup.

Understanding the locomotor characteristics of competition can help rugby league (RL) coaches optimise training prescription. To date, no research exists on the locomotor characteristics of women's RL. The aim was to compare whole match and peak locomotor characteristics of women's RL competition at international (RL World Cup [WRLWC]) and domestic level (Super League [WSL]). Microtechnology data were collected from 58 players from 3-WSL clubs and 1-WRLWC team. Participants were classified into forwards (n = 30) and backs (n = 28). Partial least squares correlation analysis established which variables were important to discriminate between the level of competition (international vs. domestic) and positional group (forwards vs. backs). Linear mixed-effects models estimated the differences between standards of competition and positional group for those variables. International forwards were most likely exposed to greater peak 1-min average acceleration (standardised mean difference = 1.23 [0.42 to 2.04]) and peak 3-min average acceleration (1.13 [0.41 to 1.85]) than domestic forwards. International backs likely completed greater peak 1-min average acceleration (0.83 [0.08 to 1.58]) than domestic backs and possibly greater high-speed-distances (0.45 [-0.17 to 1.07]). Findings highlight the need for positional specific training across levels to prepare representative players for the increased match characteristics of international competition.

Validity of an Isometric Midthigh Pull Dynamometer in Male Youth Athletes.

Till, K, Morris, R, Stokes, K, Trewartha, G, Twist, C, Dobbin, N, Hunwicks, R, and Jones, B. Validity of an isometric midthigh pull dynamometer in male youth athletes. J Strength Cond Res 32(2): 490-493, 2018-The purpose of this study was to investigate the validity of an isometric midthigh pull dynamometer against a criterion measure (i.e., 1,000-Hz force platform) for assessing muscle strength in male youth athletes. Twenty-two male adolescent (age 15.3 ± 0.5 years) rugby league players performed 4 isometric midthigh pull efforts (i.e., 2 on the dynamometer and 2 on the force platform) separated by 5-minute rest in a randomized and counterbalanced order. Mean bias, typical error of estimate (TEE), and Pearson correlation coefficient for peak force (PF) and peak force minus body weight (PFBW) from the force platform were validated against peak force from the dynamometer (DynoPF). When compared with PF and PFBW, mean bias (with 90% confidence limits) for DynoPF was very large (-32.4 [-34.2 to -30.6] %) and moderate (-10.0 [-12.8 to -7.2] %), respectively. The TEE was moderate for both PF (8.1 [6.3-11.2] %) and PFBW (8.9 [7.0-12.4]). Correlations between DynoPF and PF (r 0.90 [0.79-0.95]) and PFBW (r 0.90 [0.80-0.95]) were nearly perfect. The isometric midthigh pull assessed using a dynamometer underestimated PF and PFBW obtained using a criterion force platform. However, strong correlations between the dynamometer and force platform suggest that a dynamometer provides an appropriate alternative to assess isometric midthigh pull strength when a force platform is not available. Therefore, practitioners can use an isometric midthigh pull dynamometer to assess strength in the field with youth athletes but should be aware that it underestimates peak force.

Criterion and Construct Validity of an Isometric Midthigh-Pull Dynamometer for Assessing Whole-Body Strength in Professional Rugby League Players.

PURPOSE: To examine the criterion and construct validity of an isometric midthigh-pull dynamometer to assess whole-body strength in professional rugby league players. METHODS: Fifty-six male rugby league players (33 senior and 23 youth players) performed 4 isometric midthigh-pull efforts (ie, 2 on the dynamometer and 2 on the force platform) in a randomized and counterbalanced order. RESULTS: Isometric peak force was underestimated (P < .05) using the dynamometer compared with the force platform (95% LoA: -213.5 ± 342.6 N). Linear regression showed that peak force derived from the dynamometer explained 85% (adjusted R2 = .85, SEE = 173 N) of the variance in the dependent variable, with the following prediction equation derived: predicted peak force = [1.046 × dynamometer peak force] + 117.594. Cross-validation revealed a nonsignificant bias (P > .05) between the predicted and peak force from the force platform and an adjusted R2 (79.6%) that represented shrinkage of 0.4% relative to the cross-validation model (80%). Peak force was greater for the senior than the youth professionals using the dynamometer (2261.2 ± 222 cf 1725.1 ± 298.0 N, respectively; P < .05). CONCLUSION: The isometric midthigh pull assessed using a dynamometer underestimates criterion peak force but is capable of distinguishing muscle-function characteristics between professional rugby league players of different standards.

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.

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.