A comparison of different heat maintenance methods implemented during a simulated half-time period in professional Rugby Union players

Abstract

<p><i>Objectives:</i> In thermoneutral conditions, half-time is associated with reductions in body temperature that acutely impair performance. This laboratory-based study compared active, passive, and combined methods of half-time heat maintenance.</p><p> <i>Design:</i> Randomised, counterbalanced, cross-over.</p><p> <i>Methods:</i> After a standardised warm-up (WU) and 15 min of rest, professional Rugby Union players (<i>n</i> = 20) completed a repeated sprint test (RSSA1). Throughout a simulated half-time (temperature: 20.5 ±0.3◦C; humidity: 53± 5%), players then rested (Control) or wore a survival jacket (Passive) for 15 min, or per-formed a 7 min rewarm-up after either 8 min of rest (Active), or 8 min of wearing a survival jacket (Combined). A second RSSA (RSSA2) followed. Core temperature (T_core) and peak power output (PPO; during countermovement jumps; CMJ) were measured at baseline, post-RSSA1, pre-RSSA2.</p><p> <i>Results:</i> All half-time interventions attenuated reductions in T_core (0.62± 0.28◦C) observed in Control (Passive: −0.23± 0.09◦C; Active: −0.17± 0.09◦C; Combined: −0.03± 0.10 ◦C, all <i>p</i> < 0.001) but Combined preserved T_core the most (<i>p</i> < 0.001). All half-time interventions attenuated the 385± 137 W reduction in Control PPO (Passive: −213± 79 W; Active: −83± 72 W; Combined: +10± 52 W; all <i>p</i> < 0.001); with best PPO maintenance in Combined (<i>p</i> ≤ 0.001). The fastest sprints occurred in RSSA2 in Combined (6.74± 0.21 s; <i>p</i> < 0.001) but Passive (6.82± 0.04 s) and Active (6.80± 0.05 s) sprints were 0.4% (<i>p</i> = 0.011) and 0.8% (<i>p</i> = 0.002) quicker than Control (6.85± 0.04 s), respectively.</p><p> <i>Conclusions:</i> While the efficacy of passive and active heat maintenance methods was supported through-out a simulated half-time, a combined approach to attenuating heat losses appeared the most beneficial for T_core and subsequent PPO and sprint performance in professional Rugby Union players.</p>