• Effects of a competitive soccer match on jump performance and interlimb asymmetries in elite academy soccer players

      Bromley, Tom; Turner, Anthony; Read, Paul; Lake, Jason; Maloney, Sean J.; Chavda, Shyam; Bishop, Chris (Lippincott, Williams & Wilkins, 2021-06-01)
      The purpose of this study was to investigate the effects of a competitive soccer match on jump performance and interlimb asymmetries over incremental time points during a 72-hour period. Fourteen elite adolescent players from a professional English category 3 academy performed single-leg countermovement jumps pre, post, 24-, 48-, and 72-hour post-match on a single force platform. Eccentric impulse, concentric impulse, peak propulsive force, jump height, peak landing force, and landing impulse were monitored throughout. Interlimb asymmetries were also calculated for each metric as the percentage difference between limbs. Significant negative changes (p < 0.05) in jump performance were noted for all metrics at all time points, with the exception of jump height. Interlimb asymmetries were metric-dependent and showed very large increases, specifically post-match, with a trend to reduce back toward baseline values at the 48-hour time point for propulsive-based metrics. Asymmetries for landing metrics did not peak until the 24-hour time point and again reduced toward baseline at 48-hour time point. This study highlights the importance of monitoring distinct jump metrics, as jump height alone was not sensitive enough to show significant changes in jump performance. However, interlimb asymmetries were sensitive to fatigue with very large increases post-match. More frequent monitoring of asymmetries could enable practitioners to determine whether existing imbalances are also associated with reductions in physical performance or increased injury risk.
    • The reliability and validity of a soccer-specific non-motorised treadmill simulation (intermittent soccer performance test)

      Aldous, Jeffrey William Frederick; Akubat, Ibrahim; Chrismas, Bryna C.; Watkins, Samuel L.; Mauger, Alexis R.; Midgley, Adrian W.; Abt, Grant; Taylor, Lee; University of Bedfordshire; Newman University; et al. (Lippincott, Williams & Wilkins, 2014-07-01)
      The current study investigated the reliability and validity of a novel non-motorised treadmill (NMT) based soccer simulation utilising a novel activity category called a ‘variable run’ to quantify fatigue during high-speed running. Twelve male University soccer players completed three familiarisation sessions and one peak speed assessment before completing the Intermittent Soccer Performance Test (iSPT) twice. The two iSPT’s were separated by 6 – 10 days. The total distance, sprint distance and high-speed running distance were 8968 ± 430 m, 980 ± 75 m and 2122 ± 140 m, respectively. No significant difference (p>0.05) was found between repeated trials of the iSPT for all physiological and performance variables. Reliability measures between iSPT1 and iSPT2 showed good agreement (CV: <4.6%; ICC: >0.80). Furthermore, the variable run phase showed high-speed running distance significantly decreased (p<0.05) in the last 15 min (89.24 ± 6.16 m) compared to the first 15 min (85.38 ± 7.28 m), quantifying decrements in high-speed exercise compared to previous literature. The current study validates the iSPT as a NMT based soccer simulation compared to previous match-play data, and is a reliable tool for assessing and monitoring physiological and performance variables in soccer players. The iSPT could be utilised in a number of ways including player rehabilitation, understanding the efficacy of nutritional interventions, and also the quantification of environmentally mediated decrements upon soccer-specific performance. 
    • Unilateral stiffness interventions augment vertical stiffness and change of direction speed

      Maloney, Sean J.; Richards, Joanna C.; Jelly, Luke; Fletcher, Iain M. (Lippincott, Williams & Wilkins, 2017-07-13)
      It has previously been shown that pre-conditioning interventions can augment change of direction speed (CODS). However, the mechanistic nature of these augmentations has not been well considered. The current study sought to determine the effects of pre-conditioning interventions designed to augment vertical stiffness on CODS. Following familiarization, ten healthy males (age: 22 ± 2 years; height: 1.78 ± 0.05 m; body mass: 75.1 ± 8.7 kg) performed three different stiffness interventions in a randomized and counterbalanced order. The interventions were: a) bilateral-focused, b) unilateral-focused, and c) a control of CODS test practice. Vertical stiffness and joint stiffness was determined pre- and post-intervention using a single leg drop jump task. CODS test performance was assessed post-intervention using a double 90o cutting task. Performances following the unilateral intervention were significantly faster than control (1.7%; P = 0.011; d = -1.08), but not significantly faster than the bilateral intervention (1.0% faster; P = 0.14; d = -0.59). Versus control, vertical stiffness was 14% greater (P = 0.049; d = 0.39) following the unilateral intervention and 11% greater (P = 0.019; d = 0.31) following the bilateral intervention; there was no difference between unilateral and bilateral interventions (P = 0.94; d = -0.08). The findings of the current study suggest that unilateral pre-conditioning interventions designed to augment vertical stiffness improve CODS within this experimental cohort.