• The concurrent validity of a rugby-specific Yo-Yo Intermittent Recovery Test (Level 1) for assessing match-related running performance

      Dobbin, Nick; Highton, Jamie M.; Moss, Samantha L.; Hunwicks, Richard; Twist, Craig; University of Chester; Rugby Football League, Leeds (Lippincott, Williams & Wilkins, 2018-06-01)
      This study investigated the concurrent validity of a rugby-specific high-intensity intermittent running test (HIIR) 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 IR1, of which sixteen also completed the Yo-Yo IR1, and 2 x ~20 min bouts of a simulated match-play (RLMSP-i). Most likely reductions in relative total, low-speed and high-speed distance, mean speed and time above 20 W·kg-1 (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 measure of load during the RLMSP-i suggests 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.
    • Criterion and construct validity of an isometric mid-thigh pull dynamometer for assessing whole body strength in professional rugby league players

      Dobbin, Nicholas; Hunwicks, Richard; Jones, Ben; Till, Kevin; Highton, Jamie M.; Twist, Craig; University of Chester, Rugby Football League, Leeds Beckett University (Human Kinetics, 2018-02-31)
      Purpose: The purpose of this study was to examine the criterion and construct validity of an isometric mid-thigh pull dynamometer to assess whole body strength in professional rugby league players. Methods: Fifty-six male rugby league players, (33 senior and 23 youth professional players) performed four isometric mid-thigh pull efforts (i.e. two on the dynamometer and two on the force platform) in a randomised and counterbalanced order. Results: Isometric peak force was underestimated (P<0.05) using the dynamometer compared to the force platform (95% LoA: -213.5 ± 342.6 N). Linear regression showed that peak force derived from the dynamometer explained 85% (adjusted R2 = 0.85, 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 non-significant bias (P>0.05) 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 compared to youth professionals using the dynamometer (2261.2 ± 222 cf. 1725.1 ± 298.0 N, respectively; P<0.05). Conclusion: The isometric mid-thigh 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, Nicholas; Hunwicks, Richard; Highton, Jamie M.; Twist, Craig (2017-11-14)
      This study assessed the inter-day 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; body mass 89.0 ± 11.6 kg) from three 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 three separate occasions. Between-day intraclass correlation coefficient, typical error (TE), coefficient of variation (CV) 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 inter-day 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 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 portable jump mat for assessing countermovement jump performance in elite rugby league players

      Dobbin, Nicholas; Hunwicks, Richard; Highton, Jamie M.; Twist, Craig; University of Chester; Rugby Football League, Leeds (Thieme Publishing, 2016-12-08)
      Validity of a portable jump mat for assessing countermovement jump performance in elite rugby league players
    • Validity of an isometric mid-thigh pull dynamometer in male youth athletes

      Till, Kevin; Morris, Rhys; Stokes, Keith; Trewartha, Grant; Twist, Craig; Dobbin, Nicholas; Hunwicks, Richard; Jones, Ben (2017-11-16)
      The purpose of the present study was to investigate the validity of an isometric mid-thigh 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 four isometric mid-thigh pull efforts (i.e., two on the dynamometer and two on the force platform) separated by 5 minutes rest in a randomised 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 to 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 to 11.2] %) and PFBW (8.9 [7.0 to 12.4]). Correlations between DynoPF and PF (r 0.90 [0.79 to 0.95]) and PFBW (r 0.90 [0.80 to 0.95] were nearly perfect. The isometric mid-thigh 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 mid-thigh pull strength when a force platform is not available. Therefore, practitioners can use an isometric mid-thigh pull dynamometer to assess strength in the field with youth athletes but should be aware that it underestimates peak force.