Practical cooling manoeuvres during simulated soccer in the heat

Abstract

The globalisation of soccer match-play has meant that major international and domestic competitions typically occur in hot environments with ambient temperature exceeding 28°C (Taylor and Rollo, 2014). Previous simulated (Aldous et al., 2016) and soccer match-play data (Mohr et al., 2012) in the heat (30 - 43°C) have reported significant reductions in physical performance measures when compared to a temperate environment (18 - 21°C). Practical strategies to reduce these heat-mediated decrements in physical performance whilst fitting in with the time constraints practitioners are faced with in soccer are warranted (Taylor and Rollo, 2014; Russel et al., 2015). Therefore, the aim of the present investigation is to examine the efficacy of practical cooling manoeuvres which can be actively worn during a pre-match warmup and whilst conducting general changing room preparatory tasks (downtime prior to kick off and half-time) on simulated soccer performance in a hot environment (32°C and 60% rH; WBGT: 28°C). Seven male university level soccer-players completed one Yo-Yo Intermittent Recovery Test level 1, two familiarization sessions, one peak speed assessment and four randomized, counterbalanced experimental trials of the intermittent Soccer Performance Test (iSPT) at 32°C. Four experimental trials consisted of cooling during a soccer-specific prematch warm-up (~24 min), downtime prior to kick-off (12 min) and half-time interval (10 min) via (1) Ice Vest (VEST); (2) Neck Cooling (NECK); (3) VEST and NECK (VEST+NECK) used concurrently; or with no-cooling (CON). Physical performance [total distance (TD), highspeed distance (HSD), sprint distance, variable run distance (VRD) and low-speed distance (LSD) covered], body temperatures [rectal temperature (Tre), mean skin temperature (Tsk) and neck temperature (neckTsk)], physiological [heart-rate (HR) and change in body-mass] and perceptual response [rate of perceived exertion (RPE), thermal comfort (TC), thermal sensation (TS) and neck thermal sensation (TSneck)] were all measured. When compared to CON, sprint distance covered was significantly improved (P < 0.05) during the first and last 15 min in NECK, final 15 min in VEST, and final 30 min in VEST+NECK during iSPT, respectively. In xvi VEST, Tsk was significantly reduced (P < 0.05) until 15 min of iSPT compared to CON. In NECK and VEST+NECK, TSneck and neckTsk were significantly reduced (P < 0.01) prior to the start of iSPT with neckTsk also significantly lower post half-time cooling, compared to CON. Furthermore, VEST+NECK also significantly reduced (P < 0.05) TS prior to the start of iSPT, compared to CON. No further significance (P > 0.05) was observed for physical performance, physiological or perceptual responses during iSPT for all conditions. Pre- and half-time cooling via VEST+NECK was most ergogenic and significantly improved sprint performance during the final 30 min of iSPT in 32°C, important given the prominence of sprinting prior to goals and assists during soccer match-play (Faude et al., 2012). Further research with a larger sample size is warranted to further elucidate the mechanisms for the enhanced performance.