Feature Dr Jodi Richardson 31

InsIde Football Wednesday, February 10, 2010

WE’VE all experienced our fair share of “heat stress” over the summer months but thank-

fully most of us can restrict our activ-ity levels and park ourselves in front of an air conditioner.

Spare a thought for AFL players who have been training in the heat and will undoubtedly endure very hot condi-tions during the NAB Cup and early in the 2010 premiership season.

Exercising in the heat at the inten-sity our players do, whether it be for training or match play, can put players at risk of heat stress or heat illness if the counter-measures are not put into practice.

Heat stress causes a range of symp-toms including headaches, dizziness, nausea, vomiting, cramps and fatigue.

It affects concentration and skill exe-cution and can eventuate in collapse.

In extreme cases heat stress can lead to heat stroke, which can be fatal.

Though this is highly unlikely to ever occur in the AFL, there have been 39 heat-related deaths in American foot-ball in the past 15 years!

Normal human body temperature averages 37.0 degrees but can begin to rise due to a combination of muscle activity from training or playing and heat transfer to the body when the temperature of the environment is high.

If the body is unable to dissipate this heat, symptoms of heat stress can begin to emerge.

Fortunately, there is a lot clubs can

do to protect players from the dangers associated with heat illness.

West Coast Eagles high performance manager Glenn Stewart explains that the Eagles take measures to minimise player exposure to heat and keep them cool.

“Heat stress is an important consid-eration. We consider when we train because of the heat and how well man-aged our players are,” he said.

“It is always looked at when we start putting together our training plan.”

The most common adaptation the Eagles make is to train early in the morning but Stewart said they had to weigh the risks against the rewards when making such changes.

“Sometimes in the morning there is a chance that the boys might still be half asleep so you are relying on them and their professionalism to get up and out for training,” he said.

“You are weighing that up against problematical conditions of 35 or 36 degrees later in the day.”

If needed, the Eagles wear ice vests, which are kept in an ice-slurry before use, and before activity may immerse themselves in cold plunge pools.

They also have a well air-conditioned

weight training room they can use as an “ice room” to keep cool, par-ticularly during breaks in pre-season games.

When playing in Alice Springs, they use the refrig-erated trucks provided by the AFL at half time to help cool the players.

Dr Marc Quod from the Australian Institute of Sport suggests in his research that the effectiveness of these cooling tools is to reduce a player’s core temperature so the subsequent increase in heat storage capac-ity will allow an athlete to com-plete a greater amount of work before a critical body temperature is reached.

Research has shown the use of pre-cooling in athletes low-ers both core and skin tempera-ture, as well as reducing the rate of sweating and improving endurance.

Heat stress can be an insidious problem for elite athletes as they are often unlikely to com-

plain about the symp-toms.

Stewart said the Eagles players were motivated so they were usually the last to say anything until the “damage is already in place” and they are already heat stressed.

“Because of that intense motivation they don’t often speak out but there comes a point where a player is strug-gling and you can just see it,” he said.

“They come in at the end of a drill and they are on their haunches or actually have to sit. By then it’s too late so we actually have to prevent that from occurring in the first place.”

Minimising heat stress is vital for player performance since the effects are seen on players not only during the heat exposure but also after the event.

“It takes longer to recover for the player,” Stewart said.

“You see that reflected in their wellness and sleep scores. You start to see objective signs in their wellbeing changing. You also start to see the player labour-ing in training drills and that’s reflected in GPS data so you see a change in physiological per-formance as players become heat stressed.

“That might be not just over the course of a session but over the course of a week.”

The body’s natural response to heat stress is to sweat. This

enables it to dissipate heat through evaporation.

As AFL clubs drive their players through increasingly gruelling pre-seasons, heat stress is an ever-present concern.

n Continued Page 32

FEELING THE HEAT!

‘There have been 39 heat-related deaths in American football in the past 15 years!’ X