Heat breaks reduce thermal stress

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This laboratory based study has shown that simple strategies (including heat breaks, cold water and the use of ice towels) can reduce heat stress in trained football players. These are very practical and can be incorporated into a football match – even when games are played in the most remote or basic conditions.

Football is a global sport and as a result it is frequently played in stressful thermal conditions. At a community or recreational level there is often limited support or infrastructure available to treat heat illness, while at an elite level there are also challenges to mitigating this problem. Games are often scheduled according to commercial demands meaning that it may not be possible to schedule them to avoid extreme heat. To try to combat the risk posed by extreme heat FIFA has introduce brief heat breaks (one in each half) when heat stress is high. These breaks occur after 30-minutes of match-play as it has been shown that this coincides with peak player core temperature. The aim of the current study was to investigate the effect of these heat breaks, and the cooling strategies used by many teams1.

Participants in this study completed four simulated football matches at 35° ambient temperature, 55% relative humidity and 30° wet bulb globe temperature (WBGT). In addition to completing a match played under ‘normal’ rules, each participant completed a further three sessions using different cooling strategies. These were a 3-minute cooling break (in each half) where they consumed chilled water, a match with a cooling break with chilled water and ice towels and a match with an extended half time (20 minutes total) and no additional cooling breaks.

All three of the cooling strategies that were investigated were shown to reduce thermal strain – but did not differ substantially in their efficacy. When using the cooling strategies in the study participants maintained a lower core temperature and recorded lower measures of exercise intensity (heart rate and session RPE). The magnitude of the core temperature reduction appears to be clinically relevant as it is similar to that seen through adaptations during heat acclimation (a reduction of between 0.21-0.28°C).

The study results are limited by the relatively small sample size, the relatively high rate of dropout (due to unrelated football injuries and illnesses) and the fact that it was conducted in a laboratory setting. Nonetheless it does illustrate that some very simple strategies can reduce heat stress. Cooling breaks (either during a game or via an extended half-time break), consuming cool liquids and the use of ice towels (and other external cooling methods) are all effective ways to help keep players safe in hot conditions.

To learn more about the impact of the playing environment please complete the ‘Environment’ module in the FIFA Diploma in Football Medicine.

1Chalmers S, Siegler J, Lovell R et al. Brief in-play cooling breaks reduce thermal strain during football in hot conditions. J Sci Med Sport (2019), https://doi.org/10.1016/j.jsams.2019.04.009

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15 May 2019 21:07

Nice article. I would love to see how this compares with youth and high/secondary school level players getting heat breaks.

Mark Fulcher
20 May 2019 8:55
Reply to  drlabelle

That is an interesting though. What do you think might happen in this setting? Would you expect to see a different result?

My thinking is that there is likely to be a similar absolute response to the cooling breaks. I wonder whether there might be a greater swing in terms of temperature change. As kids are more susceptible to the heat perhaps they will be marginally hotter and may cool faster?

16 May 2019 10:59

Hello everyone – I have the experience of this situation, using a cold water bucket that was done in half a game for twenty seconds in two rounds

Mark Fulcher
20 May 2019 8:53

Working for New Zealand Football we frequently travel to the Pacific Islands to play. It is typically very hot there, humid and with high exposure to solar radiation. We have trialled lots of different cooling strategies including ice vests, ice slurry/slushies and pre-cooling. While there is scientific data to support each of these strategies the players did not like them and they were logistically challenging. In our experience consuming regular cooled fluids, heat breaks and ice towels were by far the most effective and most well received strategies.

Dr. János Tóth jr.
21 May 2019 4:06

That’s why here in Miami, at the youth games have practically quarters, not halves! High heat and huminity.
But my strongest expeience was in Vietnam (south).

23 May 2019 5:13

Hi all,
Coming from the Middle East, the June- August period is considered as the worst time to train or perform any sort of activity. The clubs travel to a much cooler place during that period or they train indoor so as to acclimatize to the temperate conditions rather than getting severe dehydration and heat stroke.

Chandramohan Murugesan
26 May 2019 3:59

Interesting study… Thanks for sharing. I wonder if there was a specific type of ‘cooling drinks’ was used i.e Hypotonic/ Isotonic/ Hypertonic?

30 May 2019 19:02

En physiologie du sport nous avons 3 phénomènes qui peuvent influencer sur la performance.ce sont 1_LA CHALEUR 2_L ALTITUDE 3-LE FROID Pour le cas précis de la chaleur il faut éviter la DESHYDRATATION(sport et chaleur ne font pas menage) Noir sans soif Jouer une compétition sous une chaleur le corps prêt en eau et sel L air chaud et le soleil font grimper la température du corps.les muscles qui se contractent produisent de la chaleur. En pratiquant le sport dans le froid ou la chaleur il faut prendre des mesure de prudence.augmentation du rythme cardiaque Bien s hydrater avant pendant… Read more »