PREVENTING HEAT ILLNESS IN SPORT

PREVENTING HEAT ILLNESS IN SPORT

This is achieved by:

STRATEGIES FOR REDUCING THE RISK OF HEAT ILLNESS (General Population)

The following strategies are intended for the general population that does not fall into any of the listed ‘At Risk’ categories. ‘At Risk’ participants should consult the recommendations for their particular population sector.

1.Timing of games

Games and sporting activities involving moderate to high intensity exercise should be scheduled to avoid conditions where ambient temperature exceeds or is likely to exceed 36 degrees Celsius or where WBGT exceeds 30 degrees Celsius.

In most parts of Australia players are likely to be exposed to their highest risk of heat injury in the months of December, January and February, although in some regions this

level of risk extends into March and April. This is in part due to high ambient temperatures that are prevalent during this period, and lack of match fitness of players participating in traditional winter sports such as Australian Rules Football.

Where possible, especially in January and February, games should be scheduled to start before 9 am. or after 6pm. Early morning or night games minimise the risk of encountering unacceptable conditions at these times of year. This is especially so where these games are to be played in a locations with a history of relatively high WBGT.

2. Acclimatisation

If games or activities are to be conducted after long periods of cooler conditions,participants should strive to be fully acclimatised prior to participation.

Physiological adaptations to exercising in the heat are rapid and can occur after 3-5 days in a hot environment. Full acclimatisation can take 10-14 days or longer. The initial response is an expansion of the plasma volume;

then, over several days, this returns to normal and the sweat rate increases with sweating starting earlier and a more dilute sweat being produced.

There is evidence that exercising in sweat clothing to the point where heat strain is

induced can give some degree of acclimatisat ion (Dawson et al). The training must induce heat strain over several days, and care must be taken that adequate hydration occurs during these training sessions.

Doing some form of submaximal exercise in a heat chamber will also give some degreeof acclimatisation; but its practicality in a team sport, exceptpossibly in individual cases,is limited.

Some level of acclimatisation will occur in players coming out of summer. This, however, is usually countered by the lack of match fitness in athletes at this time of year.

What can be done easily is to educate athletes to train themselves to play and train with copious fluids already on-board. Further it must be emphasised to the players that they MUST consume fluids containing 6%-8% carbohydrate - in warm/hot conditions, muscle glycogen utilisation is much higher. (Febbraio 1992). The consumption of carbohydrate containing fluids has been proven to improve performance in the heat and, more importantly, delay the onset of exercise-induced heat exhaustion (Febbraio 1992, Davies et al 1988) and, hence, probably help prevent heat stroke.

3. Hydration

The more athletes sweat, the more fluid they must consume to avoid dehydration. High levels of dehydration may increase the risk of heat stress. To diminish the risk of heat stress fluid should be consumed before, during and after activity. It is recommended participants drink at least 7-8 ml of fluid per kg of body mass (average is about 2 cups) no more than 2hours before exercising to promote adequate hydration and allow time for excretion of excess water.

During exercise it is recommended that participants should drink fluid at regular intervals to replace water lost through sweating. Participants should aim to drink at least 3 ml per kg of body mass (about 250 ml for the average athlete of around 70kilograms every 15 to 20 minutes or 2–3 cups every hour). However, this may vary dependent on the rate of sweating. Fluid taken should be cooler than the ambient temperature.

Water is considered an adequate fluid option for activities lasting up to one hour. Participants in events or activities exceeding one hour are recommended to use carbohydrate-based sports drinks as a means of replacing fluids, carbohydrates and electrolytes lost during prolonged activity. In high risk conditions players should be encouraged to drink fluids at scheduled drinks breaks and should be provided convenient access to fluids during activity without unnecessary interruption to the game or event.

Officials and event organisers should also consider including additional drinks breaks for players in conditions of high risk. In regard to post-event rehydration, it needs to be remembered that this can take 24hours or more.

4. Player rest and rotation

CHILDREN AND HEAT

The physiological and structural difference between children and adults places children at a greater risk of suffering from heat illness. These differences impact on a child’s ability to respond to environmental heat and acclimatise to heat. These differences include:

• a larger surface area/body mass ratio which affects their ability to dissipate heat when environmental temperature is greater than skin temperature (Falk 1998). This can be an advantage when heat loss is necessary, but is a disadvantage when radiant or convective heat gain occurs;
• immature sweating mechanisms which require a greater increase in body temperature before the onset of sweating (Araki et al 1979); and
• fewer and smaller sweat glands which limit the production of sweat (Araki et al 1979, Falk 1998, Wagner et al 1974).

HOT WEATHER POLICY FOR CHILDREN

At ambient temperature greater than or equal to 30 degrees Celsius, children have greater difficulty getting rid of heat than adults.

STRATEGIES FOR REDUCING THE RISK OF HEATILLNESS (Children)

The following strategies should be considered for sport and physical activities involving children. The strategies should be considered in conjunction with strategies for reducing the risk of heat illness for the general population and the hot weather policy for children.

1. Shade and drinks

Organisers of activities that are conductedin hot conditions must provide sufficient shade and regular drinking opportunities. This is particularly critical where the fitness and state of acclimatisation of the young participants are uncertain.

It is recommended that water or fluids be provided whenever children are being active. More fluid, however, appears to be consumed by young people when the drinks offered are perceived as palatable to them. Therefore, for children and adolescents having trouble drinking adequate tap water, flavoured drinks may need to be considered. Conversely, the high energy content of some flavoured drinks may be unnecessary during exercise in athletes who have a genuine rather than an aesthetic need to lower body fat levels.