Pre-cooling for team-sports: Does it work and is it required?

Hockey player wearing an ice vest
Author:  Rob Duffield, School of Human Movement, Charles Sturt University and Aaron Coutts, School of Leisure, Sport and Tourism, University of Technology, Sydney
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 (Arngrímsson 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.

While it seems whole body pre-cooling can provide benefits to team-sport exercise performance, it generally requires whole-body pre-cooling which can be costly and logistically difficult.  For example, having to immerse players in cool water as the part of their pre-match routine (when other commitments are present) may not be practical.  Additionally, arranging facilities to pre-cool large groups of players may also be logistically difficult.  As such, while pre-cooling may be beneficial for improving performance, the practicalities of implementing this in a competition environment may reduce its ability to be implemented in most team sports. As such, this raises the question as to whether the potential benefits are worth the costs involved with the logistics of pre-cooling.

Is pre-cooling required?

Many laboratory-based studies have shown that core temperature can increase rapidly during intermittent-sprint exercise in the heat (Drust et al. 2005), yet very little in-game data is available from team-sports to support these lab-based conclusions. Recently, Edwards and Clark (2006) have published core temperature data collected by telemetric pills from recreational and professional English soccer players (in mild environmental conditions). They reported that average core temperature rose to slightly above 39oC during games, however, some players were close to reaching 40oC (above 40oC an increased risk of debilitating heat stress is apparent). In addition, recently unpublished research we have conducted found similar results from elite AFL players, finding an average core temperature of 39.1oC during warm - hot (28 - 30oC) pre-season AFL games. While the average core temperature of 39oC is not of high physiological concern, several individual players peaked at 40.0oC. Further, a majority of players reached peak core temperatures during the first half of the game. Therefore, while the (average) group data may indicate that core temperature and hence thermal stress does not reach values that may impact on health, individual data indicates that particular (often highly mobile) players can reach precarious levels of physiological heat strain. Importantly, no cases of heat illness were reported in the players who achieved core temperatures around 40oC.  However, the fast rate of rise to reach peak core temperatures in the first half of AFL football in the heat could potentially affect performance later in the game. Therefore, the use of pre-cooling procedures may be of benefit for specific individual players.

Summary and practical implications.

As a result of the information obtained from recent research, some further thoughts on strategies for pre-cooling in team-sports can be offered;

  • Whole body pre-cooling is the more effective cooling procedure and can be effective in improving team-sport performance; however, the logistics of providing this service for all athletes on game day is difficult (although easier in recent years with the advent of portable recovery pools).
  • In-game data from elite football players indicates that  average core temperature reaches relatively stable levels of ƒî39oC, however individual data indicates some players can reach ~40oC in the first 25-min (generally highly mobile players).
  • The duration of pre-cooling effects are finite (30 min), so it is important to maintain cooling procedures until as close as possible to game time.
  • Therefore, a possible strategy involves selecting players potentially at a high risk of encountering excessive thermal stress and performing whole body pre-cooling (at the expense of other less active players) and continue cooling with ice-vests or air-conditioned rooms until as close as possible to game time.
  • As a final note, the implementation of these procedures are a decision for the coach and/or sports scientist as to whether the benefits outweigh the costs for effective precooling; however, understanding player game demands may lead to effective individualised pre-cooling strategies for selected players.

References

Arngrímsson SA, Petitt DS, Stueck MG, Jorgensen DK and Cureton KJ (2004)
Cooling vest worn during active warm-up improves 5-km run performance in the heat. J Appl Physiol 96: 1876 ¡V 1874.

Castle PC, Macdonald AL, Philip A, Webborn A, Watt PW and Maxwell NS (2006)
Precooling leg muscle improves intermittent sprint exercise performance in hot, humid conditions. J Appl Physiol 100: 1377 ¡V 1384. 

Drust B, Rassmussen P, Mohr M, Nielsen B and Nybo L (2005) Elevations in core
and muscle temperature impairs repeated sprint performance. Acta Physiol Scand 183: 181 ¡V 190.

Duffield R, Dawson B, Bishop D, Fitzsimons M and Lawrence S (2003) Effect of
wearing and ice cooling jacket on repeat sprint performance in warm/humid conditions. Br J Sports Med 37: 164 ¡V 169.

Duffield R and Marino, FE, in press, 'Effects of precooling procedures on intermittent-
sprint exercise performance in warm conditions'. Eur J Appl Physiol

Edwards AM and Clark NA (2006) Thermoregulatory observations in soccer match
play: professional and recreational level applications using an intestinal pill system to measure core temperature. Br J Sports Med 40: 133 ¡V 138.

Gonzalez-Alonso J, Teller C, Anderson SL. Jensen FB, Hyldig T and Nielsen B
(1999) Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J Appl Physiol 86: 1032 ¡V 1038.


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