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Beating the heat

With temperature up above normal, athletes are at risk of heat injury and dehydration Despite the fact that parts of Canada are suffering their worst droughts in more than three decades, and that daily temperatures across the country are breaking rec

With temperature up above normal, athletes are at risk of heat injury and dehydration

Despite the fact that parts of Canada are suffering their worst droughts in more than three decades, and that daily temperatures across the country are breaking records with no relief in sight, summer sports are in full swing.

The World Track and Field Championships in Edmonton, Alberta wrapped up with a scorching 35 degree Centigrade afternoon, and the Canada Games kicked off in London, Ontario this weekend with temperatures in the low 30s and higher than normal humidity.

In the U.S., the heat wave has gotten a lot of press with the death of two football players from heat stroke. Korey Stringer, an offensive lineman for the Minnesota Vikings, died on Aug. 8 of heat stroke, less than a week after University of Florida fullback Eraste Autin met the same fate. Stringer’s core body temperature was measured 108 degrees Farenheit (42.2 degrees Celsius) when he collapsed.

On Aug. 10, Rashidi Wheeler, a 22 year old football player for Northwestern University in Chicago died of an asthma attack that was likely worsened by the heat and his own heat-weakened conditions.

These deaths have sparked an interest in the prevention, recognition and treatment of heat-related illnesses such as dehydration and heat stroke. Athletic trainers and medical staff are monitoring the situation closely at the Canada Games, and coaches everywhere are lightening their training regimens until temperatures drop.

There have been no reported cases of dehydration or heat stroke at the Whistler Health Care Centre. But with temperatures reaching 30 degrees daily and warm weather likely to continue through the weekend, a little knowledge can go a long way.

According to the International Olympic Committee’s 2000 Sport Medicine Manual, risk of heat injury – a catchall term for all heat and dehydration injuries – is dependent on both the external environment and the athlete. The environmental factors include high temperature, high relative humidity (which results in decreased evaporation of sweat), increased solar radiation, and the absence of wind.

Athlete factors that contribute to heat injury include illness (such as fever, infection, recent vomiting and diarrhea), injury, lack of heat acclimatization (you need between four and eight days training at race temperature to improve evaporation), sunburn, excessive sun block (which reduces evaporative cooling, fatigue, excessive clothing, dark clothing, and rubberized clothing that prevents heat dissipation, and dehydration from a lack of fluid intake before and during the race in quantities that match your race pace.

"The real problem with heat stroke is that you have an increased rate of heat production that’s not being met by an equivalent rate of heat loss," says Doctor Adam Kendall of the Creekside Medical Clinic. "You have to be able to dissipate that heat."

In addition to his practice as a family physician and shifts in the emergency room at the Whistler Health Care Centre, Kendall has pursued his own personal interest in sports medicine by studying the journals and working with athletes. He goes mountain biking almost every day, skis, and has been active in team sports since he played Rugby for Canada and the University of British Columbia.

As a player and as a doctor, he has seen his share of heat-related injuries.

"Different things are happening to your body and there are different kinds of heat injuries, so you have to pay attention to what’s going on. How do you look, how do you feel, are you sweating a lot, are you not sweating at all… you to be able to recognize the symptoms before they get worse and your heat injury or dehydration becomes a serious problem."

There are three types of heat injury, and different stages of dehydration to watch out for.

The first type of heat injury is heat cramps, or cramping in your limps that cannot be relieved by stretching. They can be treated by fluid replacement, ice massage, and continued static stretching of the muscle.

The second type is heat exhaustion, which is manifested by a headache; tingling in your arms, legs and back; fatigue; muscle cramps; chills or shivering; profuse sweating; a rapid, weak pulse; pale, moist, cool skin and a temperature of less than 40 degrees Celsius, and hypotension (low blood pressure).

The third and most severe type is heat stroke.

"Heat stroke is a mostly rare condition when you have a temperature that’s usually above 40 degrees Celsius and you’re system is deteriorating," says Dr. Kendall. "A lot of people who were out in the sun all day will say they have heat stroke, but it’s usually just exhaustion or dehydration – heat stroke is a serious medical condition."

Signs of heat stroke include headaches; convulsions; loss of consciousness, coma; rapid, full pulse; hot, red skin with or without sweating; temperatures above 40 degrees Celsius, and ataxia (a condition affecting the muscles and nervous system).

To treat heat exhaustion and stroke, you will need to stop and get out of the heat, if possible. Remove insulating clothing, and cool down by packing ice around your major blood vessels and covering yourself with a wet towel. If possible, get into some cool (not cold) water.

Rehydrate by mouth if possible. If you’re unconscious or ill, intravenous rehydration may be necessary.

You should monitor your vital signs closely, including consciousness and urinary output. If you have mild heat exhaustion, you can probably treat yourself. If you’re seriously ill or deteriorating, you may require medical attention.

Dehydration is a usually a factor in all types of heat injuries, but it can exist on its own without any of the other symptoms.

The first sign of dehydration is generally thirst. Most athletes will keep playing if they’re a little thirsty, and may not drink enough water at breaks for fear of it affecting their performance. Thirst is your body’s alert mechanism that it’s time to drink more water.

Another sign is an increased resting heart rate. "You’re heart has to work harder to pump a lower amount of blood volume around," says Dr. Kendall.

You can also feel light headed or dizzy, especially if you stand up too quickly. You become extremely fatigued, and over time your urine will start to get darker and thicker.

Performance athletes will notice reduced muscular strength, decreased performance, lower blood and plasma volumes, reduced heart function, and a higher resting heart rate.

"If you stop sweating, that’s a good sign that you’re badly dehydrated," says Dr. Kendall.

How much should you drink?

According to Dr. Kendall, it’s a good idea to start drinking before you start playing – if you start out feeling thirsty, it’s just going to get worse and worse. The recommended amount is about 500 ml of fluid two hours before training or competition.

You should continue to drink as you go. How much you drink should be determined by your body weight and how hard you’re working. Between 150 and 300 ml of fluid is recommended every 15 to 20 minutes during exercise. Drink more if it’s hot or humid.

Energy drinks with a 4 to 8 per cent carbohydrate concentration are also helpful in restoring energy, provided that the carb source isn’t fructose.

An athlete weighing 50 kilograms should drink about 600 ml an hour, or 150 ml every 15 minutes. An athlete weighing 90 kilograms should drink 1,080 ml per hour or 270 ml every 15 minutes.

Weigh yourself before an activity, then drink a litre for every kilogram of weight lost during the activity, plus up to 500 ml to compensate for urinary losses.

Compared to adults, children may need to drink more fluid more frequently because they have a slower sweat rate, a smaller surface area to release heat, and a delayed sensation of thirst.

"Prevention, as always, is the best medicine," says Dr. Kendall. Exercise during the morning or later afternoon when it’s cooler, make the most of shade, have lots of fluids on hand, be aware when there’s a risk of heat injury and make adjustments, and have the right first aid on hand to remedy the situation.

Athletes should also give themselves four to eight days to acclimatize, wear light, loose-fitting clothing that facilitates evaporation, and always hydrate beforehand.




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