• Effect of tyrosine ingestion on cognitive and physical performance utilising an intermittent soccer performance test (iSPT) in a warm environment

      Coull, Nicole; Watkins, Samuel L.; Aldous, Jeffrey William Frederick; Warren, Lee K.; Chrismas, Bryna C.; Dascombe, Ben; Mauger, Alexis R.; Abt, Grant; Taylor, Lee (Springer, 2014-10-19)
      Abstract Purpose The aim of this study was to investigate the effect of tyrosine (TYR) ingestion on cognitive and physical performance during soccer-specific exercise in a warm environment. Methods Eight male soccer players completed an individualised 90 min soccer-simulation intermittent soccer performance test (iSPT), on a non-motorised treadmill, on two occasions, within an environmental chamber (25 °C, 40 % RH). Participants ingested tyrosine (TYR; 250 mL sugar free drink plus 150 mg kg body mass−1 TYR) at both 5 h and 1 h pre-exercise or a placebo control (PLA; 250 mL sugar free drink only) in a double-blind, randomised, crossover design. Cognitive performance (vigilance and dual-task) and perceived readiness to invest physical effort (RTIPE) and mental effort (RTIME) were assessed: pre-exercise, half-time, end of half-time and immediately post-exercise. Physical performance was assessed using the total distance covered in both halves of iSPT. Results Positive vigilance responses (HIT) were significantly higher (12.6 ± 1.7 vs 11.5 ± 2.4, p = 0.015) with negative responses (MISS) significantly lower (2.4 ± 1.8 vs 3.5 ± 2.4, p = 0.013) in TYR compared to PLA. RTIME scores were significantly higher in the TYR trial when compared to PLA (6.7 ± 1.2 vs 5.9 ± 1.2, p = 0.039). TYR had no significant (p > 0.05) influence on any other cognitive or physical performance measure. Conclusion The results show that TYR ingestion is associated with improved vigilance and RTIME when exposed to individualised soccer-specific exercise (iSPT) in a warm environment. This suggests that increasing the availability of TYR may improve cognitive function during exposure to exercise-heat stress.
    • Hot and hypoxic environments inhibit simulated soccer performance and exacerbate performance decrements when combined.

      Aldous, Jeffrey William Frederick; Chrismas, Bryna C.; Akubat, Ibrahim; Dascombe, Ben; Abt, Grant; Taylor, Lee; University of Bedfordshire; Qatar University; Newman University; La Trobe University; et al. (Frontiers Media, 2016-01-12)
      The effects of heat and/or hypoxia have been well-documented in match-play data. However, large match-to-match variation for key physical performance measures makes environmental inferences difficult to ascertain from soccer match-play. Therefore, the present study aims to investigate the hot (HOT), hypoxic (HYP) and hot-hypoxic (HH) mediated-decrements during a non-motorised treadmill based soccer-specific simulation. Twelve male University soccer players completed three familiarisation sessions and four randomised crossover experimental trials of the intermittent Soccer Performance Test (iSPT) in normoxic-temperate (CON: 18oC 50% rH), HOT (30oC; 50% rH), HYP (1,000m; 18oC 50% rH) and HH (1,000m; 30oC; 50% rH). Physical performance and its performance decrements, body temperatures (rectal, skin and estimated muscle temperature), heart rate (HR), arterial blood oxygen saturation (SaO2), perceived exertion, thermal sensation (TS), body mass changes, blood lactate and plasma volume were all measured. Performance decrements were similar in HOT and HYP [Total Distance (-4%), High-speed distance (~-8%) and variable run distance (~-12%) covered] and exacerbated in HH [total distance (-9%), high-speed distance (-15%) and variable run distance (-15%)] compared to CON. Peak sprint speed, was 4% greater in HOT compared with CON and HYP and 7% greater in HH. Sprint distance covered was unchanged (p > 0.05) in HOT and HYP and only decreased in HH (-8%) compared with CON. Body mass (-2%), temperatures (+2-5%) and TS (+18%) were altered in HOT. Furthermore, SaO2 (-8%) and HR (+3%) were changed in HYP. Similar changes in body mass and temperatures, HR, TS and SaO2 were evident in HH to HOT and HYP, however, blood lactate (p < 0.001) and plasma volume (p < 0.001) were only significantly altered in HH. Perceived exertion was elevated (p < 0.05) by 7% in all conditions compared with CON. Regression analysis identified that absolute TS and absolute rise in skin and estimated muscle temperature (r = 0.82, r = 0.84 r = 0.82, respectively; p <0.05) predicted the hot-mediated-decrements in HOT. The hot, hypoxic and hot-hypoxic environments impaired physical performance during iSPT. Future interventions should address the increases in TS and body temperatures, to attenuate these decrements on soccer performance.
    • Mixed-methods pre-match cooling improves simulated soccer performance in the heat : cooling during simulated soccer

      Aldous, Jeffrey William Frederick; Chrismas, Bryna C.; Akubat, Ibrahim; Stringer, Charlotte Anne; Abt, Grant; Taylor, Lee; University of Bedfordshire; Qatar University; Newman University; University of Hull; et al. (Taylor & Francis, 2018-07-24)
      This investigation examined the effects of three pre-match and half-time cooling manoeuvres on physical performance and associated physiological and perceptual responses in eight University soccer players during a non-motorised treadmill based individualised soccer-specific simulation [intermittent soccer performance test (iSPT)] at 30oC. Four randomised experimental trials were completed; following 30-min (pre-match) and 15-min (half-time) cooling manoeuvres via: (1) ice slurry ingestion (SLURRY); (2) ice-packs placed on the quadriceps and hamstrings (PACKS); (3) mixed-methods (MM; PACKS and SLURRY concurrently); or no-cooling (CON). In iSPT first half, a moderate increase in total (Mean ± Standard Deviation: 108 ± 57m, qualitative inference: most likely, Cohen’s d: 0.87, 90%CL: ±0.31), high-speed (56 ± 46m, very likely, 0.68 ±0.38) and variable run (15 ± 5m, very likely, 0.81 ±0.47) distance covered was reported in MM compared with CON. Additionally, pre-match reductions in thermal sensation (-1.0 ± 0.5, most likely, -0.91 ±0.36), rectal (-0.6 ± 0.1oC, very likely, -0.86 ±0.35) and skin temperature (-1.1 ± 0.3oC, very likely, -0.88 ±0.42) continued throughout iSPT first half. Physical performance during iSPT first half was unaltered in SLURRY and PACKS compared to CON. Rectal temperature was moderately increased in SLURRY at 45-min (0.2 ± 0.1oC, very likely, 0.67 ±0.36). Condition did not influence any measure in iSPT second half compared to CON. Only MM pre-match cooling augmented physical performance during iSPT first half, likely due to peripheral and central thermoregulatory factors favourably influencing first half iSPT performance. Further practical half-time cooling manoeuvres which enhance second half performance are still required.
    • 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.