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"Preventing Heat Illness In Sport Policy" (PDF Document)

1. Alerting sporting bodies and participants of the risk of heat illness from physical activity in hot weather conditions.
2. Providing a clear cancellation policy for sporting bodies conducting events in hot weather conditions
3. Educating sporting bodies and participants on methods of minimising the risk of heat illness and the avoidance of situations that may worsen heat illness.

Wet Bulb Globe Temperature (WBGT) is the best measure of heat strain currently available. WBGT is not the same as Ambient or ‘Dry’ temperature as the WBGT accounts for the levels of humidity, radiation, wind movement and ambient temperature.

WBGT should be measured on site immediately prior to the start of an activity or event using a specific WBGT thermometer. This is done to ensure measurements are reflective of the conditions at which the event is to be played.

HOT WEATHER POLICY FOR THE GENERAL POPULATION

At WBGT greater than 28 degrees Celsius there is extreme risk of heat injury to all participants.

Sporting events or activities requiring moderate to intense exercise that are conducted in conditions that exceed 28 degrees WBGT should be postponed or cancelled.

Activity may be undertaken by individuals who are not categorised in any of the “at risk” groups if conditions are equivalent to the following WBGT ranges. However, strategies to reduce the risk of heat injury should be implemented particularly when high or moderate risk of heat injury is apparent.

• At WBGT between 23 and 28 degrees Celsius there is a high risk of heat injury.
• At WBGT between 18 and 22 degrees Celsius there is a moderate risk of heat injury
• At WBGT below 18 degrees Celsius there is a minimal risk of heat injury.

DISCUSSION

The risk of heat injury from high intensity sport is significant. It can range from cramps, through heat exhaustion to heat stroke, coma, and death (Mitchell, 1994).

During a competition, a competitor may produce 15 - 20 times the heat they produce at rest. Dissipation of this excess heat is primarily achieved through sweating. If the body's ability to dissipate heat is compromised, core temperature in an average size individual may rise by one degree Celsius for every five minutes of exercise if no temperature regulating mechanisms are activated (Nadel 1977). If an individual’s core temperature is above 40 degrees Celsius (normal 37 degrees) the risk of heat injury is significant.

Factors which impair the body's ability to dissipate heat are:

1. High ambient temperature
2. Solar radiation
3. Humidity (this compromises the efficacy of sweating)
4. Dehydration

These factors significantly increase the risk of heat injury occurring.

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 WBGT exceeds or is likely to exceed 28 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 a.m. or after 6 p.m. 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 acclimatisation (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 degree of acclimatisation; but its practicality in a team sport, except possibly 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 such as Gatorade has been proven to improve performance in the heat and, more importantly, delay the onset of Exercise-Induced Heat Exhaustion (Febbraio,1992, Davies etal. 1988) and, hence, probably help prevent Heat Stroke.

3. Hydration
The more an athlete sweats, the more fluid he 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 7-8ml of fluid per kg of body mass 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 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 provide a benefit for exercise that is less than one hour in duration. 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.

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 24 hours or more.

4. 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. For WBGT temperatures greater than 18 degrees Celsius and less than 23 degrees Celsius all 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 comprise at least 6 minutes during the period.

For situations where the WBGT is greater than 23 degrees Celsius and less than 28 degree Celsius, all players should be rested for at least 25% of the period they would normally participate.

This may be achieved by rotation of players through an interchange bench or via the reduction in the regular playing time for all players.

For events played in high risk conditions that do not have a specified playing time, players should be permitted to take rest breaks from activity equivalent to 3 minutes for every 30 minutes of activity.

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 and ice packs
• Providing additional fluids to allow participants to spray or douse themselves to assist cooling

5. Pre-cooling
Pre-cooling by cool water immersion or the wearing of ice vests has been demonstrated to increase athletic performance in endurance sports. This practice could be of benefit to many athletes. However, it must be noted that the effects of a pre-cooling manoeuvre are reduced rapidly by a warm up. Therefore, any pre-cooling strategy must be undertaken in concert with a vastly reduced warm-up if it is to be effective.

6. 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.

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)
• Fewer and smaller sweat glands which limits 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 34 degrees Celsius there is extreme risk of heat injury to all children and adolescents participants

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.

STRATEGIES FOR REDUCING THE RISK OF HEAT ILLNESS
(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 conducted under hot conditions must provide sufficient shade, and regular drinking opportunities. This is particularly critical where the fitness and state of acclimatization of the young participants are uncertain.

It is recommended that water or sports drinks such as Gatorade 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 such as commercially available sports 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.

It is recommended that young athletes begin regular drinking routines using water or sports drinks such as Gatorade during training and competition. Regular and effective drinking practices should become habitual to young athletes before, during, and after activity. Individuals should monitor weight changes before and after workouts and know the amount of fluid that they are likely to require. The electrolyte content of some sports drinks consumed following activity may shorten the time taken to recover, particularly in well-trained young athletes who sweat considerably more than their sedentary peers.

2. Acclimatisation and Overweight Children
In addition to the risks associated with activity in the heat for unfit and unacclimatised young people, coaches/supervisors of overweight children and adolescents should take extra precautions to lessen the potential for heat gain. It is recommended that whenever activity in hot conditions is unavoidable with these children, coaches /supervisors decrease the volume and duration of physical activity, and increase opportunities for drinking, rest, and shade as a matter of priority.

At the onset of hot weather, the young athlete may take longer to acclimatize. It is therefore recommended that training volumes (duration and intensity) decrease during the first few weeks of hot weather. Increased times for rest, using access to shade more frequently, and increasing the number of mandatory drinking breaks are recommended for the young athlete when the weather becomes noticeably hotter.

3. Clothing
In addition to the clothing recommendations made for the general population, it is recommended that summer based sporting organizations select uniforms that minimize heat gain and that coaches, teachers, and parents encourage children and adolescents to wear appropriate clothing in layers that can be easily removed during activity.

4. Heat Illness Register
To improve the understanding of children and adolescents activity in the heat, it is recommended that a register of heat-related illness be established. This may comprise a system within which all aspects of heat related illness incidents are recorded. Items of note may include the individual afflicted and their symptoms, the time of the incident, the environmental conditions, the physical activity undertaken, the immediate treatment and subsequent action taken.

The system is recommended to aid in the identification of individuals that have previously experienced some form of heat illness and therefore may require additional attention to ensure prevention strategies are adopted by these individuals.

RECOMMENDATIONS FOR THE DEVELOPMENT AND IMPLEMENTATION OF SPORTS INDUSTRY STRUCTURES TO REDUCE THE RISK OF HEAT ILLNESS

Wet Bulb Globe Temperature and its measurement are not currently considered in Australian sport except in a small number of isolated elite sporting competitions and events. The adoption of policies (General Population) that require the use of Wet Bulb Globe Temperature as the defining measurement for decisions relating to the cancellation of events are recognised as being difficult to implement . At present, issues such as cost, convenience and availability of accurate, on-site measurement of WBGT are all prohibiting factors in the adoption of appropriate policies for all sporting codes played in hot weather conditions.

The following recommendations are provided as a means of identifying long and short-term objectives for the sports industry in an endeavour to significantly reduce the risk of dangerous, and sometimes catastrophic incidents occurring as a result of activities conducted in hot weather conditions.

Adoption of Policy for Children
All junior sporting clubs and associations or clubs and associations involving junior participants should immediately adopt the stated policy for cancellation or postponement of events involving children that are likely to be played in ambient temperatures equal to or greater than 34 degrees Celsius.

All junior sporting clubs or clubs involving junior participants are encouraged to purchase a dry bulb thermometer to measure ambient air temperature on-site to ensure local conditions are accurately measured.

Adoption of Strategies
In the absence of accurate methods of measuring WBGT on-site without a suitable device, all sporting clubs and associations should develop or add to their existing policies or rules, the listed ‘Strategies for Reducing the Risk of Heat Injury’.

Central Measurement
To overcome the current barriers for sporting clubs and associations acquiring WBGT thermometers for the purpose of on-site WBGT measurement, consideration should be given to the proposal of local organisations such as local government authorities purchasing WBGT thermometers with the intention of establishing local climate services.

It is recommended that a measured WBGT figure be made available via a regularly updated web page or telephone service to which club or regional association representatives may gain access.

This is less accurate than measurements conducted on site, but can provide more accurate figures than those currently available.

Estimated Calculation
Formulae are available to estimate the WBGT. Whilst again not as accurate as direct measurement, this strategy does provide substantial guidance to event organisers and officials of the severity of the conditions and the subsequent need to cancel or postpone an activity.

The formula is as follows:
WBGT = (0.567 Tdb) + (0.393 Pa) + 3.94
Where Tdb = dry bulb thermometer temperature and Pa = environmental water pressure (ACSM 1984).
It is recommended in the absence of a WBG thermometer that this method be used to estimate WBGT.

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