• Call a Doctor or Ambulance immediately
   
• Remove from the field and lay the victim down in a cool place
   
• Give cool water to drink if conscious
   
• Cool the players by putting in a cool bath, shower or under hose, applying wrapped icepacks to the groin an armpits or use wet towels

How do we know when it is safe to play in hot conditions?

All hot environments present athletes with some level of risk. The most effective way of evaluating the risk of playing in hot weather for adults is by measuring Wet Bulb Globe Temperature (WBGT) which takes into account both ambient air temperature and humidity. This is important because the higher the humidity, the less likely cooling will occur through the evaporation of sweat.

WBGT ranges have been determined to reflect the risk of heat injury. These are as follows:

Sports Medicine Australia recommends that events or activities requiring moderate to high intensity exercise that are conducted in conditions that exceed 28 degrees WBGT should be postponed or cancelled

Measuring WBGT is done using a Wet Bulb Globe Thermometer. These devices are not readily available and are often costly. However, if a WBG Thermometer is not available, there is another way. It is possible to obtain an ambient temperature and 'dew point' readings from the Bureau of Meteorology, then use the chart below to work out the WBGT. The Bureau of Meteorology website is also useful: www.bom.gov.au

Alternatively Dew Point thermometers can also be purchased from specialist weather suppliers- allowing you to take a measurement at the site for a more accurate reading of conditions.

Calculating the Wet Bulb Globe Temperature (WBGT)

What steps can be taken to prevent players getting heat injury?

There are circumstances when players are required to participate in hot conditions. The risk of experiencing heat illness, particularly in such conditions, can be reduced by employing any of a number of strategies. These include:

1. Timing of Games

   Games and sporting activities involving moderate to high intensity exercise should be scheduled to avoid conditions where WBGT exceeds or is likely to exceed 28.

   Where possible, especially during the summer months, games should not be scheduled during the hottest part of the day (usually between 11am and 3pm, or noon and 4pm daylight saving time). Early morning or night games minimise the risk of encountering unacceptable playing conditions.

2. Hydration - Drink Up!

   The more an athlete sweats, the more fluid they must consume to avoid dehydration. High levels of dehydration may increase the risk of heat illness. To diminish the risk of heat illness fluids should be consumed before, during and after activity.

   Thirst should not be relied upon as an indicator of a participant's fluid needs. Dehydration can even occur when fluids have been consumed. It is recommended participants drink at least 7-8ml of fluid per kg of body mass (about 500 ml for a 65 kg person) no more than 2 hours 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 3ml per kg of body mass (about 250ml for the average athlete of around 70 kilograms every 15 to 20 minutes). However this may vary dependent on the rate of sweating. Fluid taken should be cooler than the ambient (air) temperature.

   Water is considered an adequate fluid option for activities lasting up to one hour, although there is evidence that sports drinks such as Gatorade do also provide a benefit.

   Participants in events or activities exceeding one hour are recommended to use carbohydrate based sports drinks such as Gatorade as a means of replacing fluids, carbohydrates and electrolytes lost during prolonged activity.

3. Player Rest and Rotation

   In conditions of high risk participants should be provided opportunities to rest through the use of player interchange or substitution. The period of rest should be determined by the WBGT at the time of the event or activity. In moderate risk conditions players should be rested for at least 10% of the period they would normally participate. For example, if the activity normally runs for 60 minutes the rest period for the player should be at least 6 minutes during the period.

   In high-risk conditions players should be rested for at least 25% of the period they would normally participate.

   The positive effects of rest breaks should also be maximised by employing the following strategies:

   • Allowing players to rest in naturally shaded areas, or providing portable structures that create shade where and when required
      
   • Providing fans, ice packs (for application to groin and armpits) or ice vests
      
   • Providing additional fluids to allow participants to spray or douse themselves
      

4. Clothing

   Light coloured, loose fitting clothes, of natural fibres or composite fabrics, with high wicking (absorption) properties, that provide for adequate ventilation are recommended as the most appropriate clothing in the heat. This clothing should further complement the existing practices in Australia that protect the skin against permanent damage from the sun.

5. Pre-cooling

   Pre-cooling by cool water immersion or the wearing of ice vests may be of benefit to many athletes. However, the effects of a pre-cooling are reduced rapidly by a warm up. Therefore, any pre-cooling strategy must done in conjunction with a vastly reduced warm-up if it is to be effective.

6. Acclimatisation

   If games or activities are to be conducted after long periods of cooler conditions participants should be fully acclimatised prior to participation. This is particularly the case at the change of climatic seasons or for participants travelling from cool to hot climates for events such as sports carnivals.

   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.

7. Other issues

   Surface Type

   A shaded /protected grass exercise surface does not retain as much heat as some other surfaces (eg solid black asphalt).

   Prior Medical Conditions

   It is important to know if any of the participating athletes have any medical condition or are taking medication that may predispose them to heat illness. Examples include asthma, diabetes, pregnancy, heart conditions and epilepsy. Some medications and conditions may need special allowances

   Any player that is experiencing a high temperature, viral infection, diarrhoea, or vomiting should be excluded from participating due to the increased risk of heat illness.

   Hats and sunscreen

   Hats and sunscreen should also be used to assist in the prevention of heat illness. Sunscreens should be water soluble.

   Sports Trainers and First Aid Personnel

   It is important to have trained personnel available to manage heat injuries. In situations where heat problems may be expected an experienced medical practitioner should be present. Heat stroke is potentially life threatening. Any indication of this condition should be immediately referred for medical assessment.

When to Cancel or Postpone

For adults: WBGT exceeds 28.
For children or adolescents: Ambient temperature 34 degrees Celsius or greater.

Children and Heat

Children's bodies are different to adults and they are at greater risk of heat illness.

At an ambient temperature greater than 34 degrees Celsius there is an extreme risk of thermal injury to all children and also adolescent participants.

SMA believes that events and activities involving children and adolescents that are conducted or scheduled for times likely to present conditions where the ambient air temperature is greater than or equal to 34 degrees Celsius should be postponed or cancelled.

For further information visit www.sma.org.au

The Tennis Coach would like to thank Sports Medicine Australia for granting permit ion to publish this article.