Pre-cooling for team-sports: Does it work and is it required?
Issue: Volume 29 Number 3
Exercise in warm or hot environmental conditions results in a rise in internal (core) body temperature that can result in a greater risk of heat illness and an ensuing decline in exercise performance (Gonzalez-Alonso et al. 1999). Team-sports requiring repeated high-intensity, intermittent-sprint efforts when played in warm to hot environments for 80+ minutes can potentially risk athlete health and performance. While the concept of pre-cooling is not new, research evidence to date is inconclusive for its effectiveness in improving team-sport exercise performance (Duffield et al. 2003). Further, while we assume that team.-sport players are at risk of heat illnesses during warm playing conditions, there is limited data on the thermal load resulting from intermittent-sprint games during actual competition. As such, the aim of this article is to discuss the relevance of some new data from recent studies that relate to the two questions posed; 1) Can pre-cooling improve team-sport performance and 2) Is it needed for team-sport games in the heat?
Does pre-cooling work?
Increased heat stress and high core temperatures have been reported to reduce the ability to perform repeated high-intensity sprints (Drust et al. 2005). As an attempt to minimise the negative effects of high core temperatures, many athletes/teams use pre-cooling methods to reduce skin and core body temperature before competition. Pre-cooling procedures are often utilised via a range of methods, including whole body cooling (ice-baths, cold rooms, showers) and individual body part cooling (ice-vests, packs, towels, spray fans). However, while the research evidence has indicated pre-cooling procedures can improve endurance performance (Arngr�msson et al. 2004), few studies have provided evidence to show that intermittent-sprint (team-sport) performance can be improved. Indeed most studies (Duffield et al. 2003) have not reported any performance benefits from pre-cooling for intermittent-sprint efforts.
Two recent studies have shown some potential pre-cooling benefit for team-sport performance (Castle et al. 2006; Duffield and Marino, in press). Castle et al. (2006) reported that 20 minutes of full lower-body pre-cooling resulted in a 4 per cent increase in peak power over a 40-minute sprint cycling exercise protocol. However, to date, this is the only study to demonstrate that power during repeated sprint efforts can be improved by pre-cooling procedures. Duffield and Marino (in press) recently showed minimal sprint performance benefits during prolonged repeated-sprint efforts but reported improvements in performance during the sub-maximal intensity exercise between each of the sprints. The major difference with this recent study and previous pre-cooling studies is that studies traditionally use sprint-efforts as the only measure of exercise performance, where in this study; both sprint and self-paced sub-maximal performance were assessed. This was achieved by performing exercise in a 20 metre heated (32oC) room where rugby players were required to perform a 15 metre sprint (with 5 metres to stop before impact with a crash mat) every minute. Each sprint was separated by sub-maximal bouts of hard running, jogging and walking (over 2 x 30 minute halves). Pre-cooling was performed with either a 15 minute ice-bath or 15 minute ice vest before wearing the ice-vest during the warm-up and at half-time. Results showed that participants in the ice-bath condition covered more distance during the hard-running bouts and more distance overall than the ice-vest or control conditions. Furthermore, skin and core temperature, heat storage and perceived effort and thermal stress during exercise were all lower in the ice-bath condition. While the ice-vest condition showed some reductions in skin temperature, there were no differences in core temperature or exercise performance when compared to the control condition. Taken together, these recent findings suggest that whole-body cooling can be more effective than part-body cooling for improving exercise performance in team-sports.