Every few Olympics comes one with hot and humid weather - Athens was hot and dry, Sydney mild, but Atlanta (1996) and Beijing (2008) had the double whammy of heat and humidity.

Physiology 102 taught us that the body secretes sweat when it’s too hot. Physics 101 told us that there is a cooling effect when water (sweat) evaporates.

However, when the air is also saturated with water vapor, sweat won’t evaporate so well and will probably fall to the ground before it has a chance to cool the skin. Since the body doesn’t get any cooler, the body continues sweating.

Obviously the hotter and more humid the weather, the more sweaty you get and hence the potential for dehydration.

These conditions motivate the sport science boffins to revisit the demands on athletes to stay cool and hydrated in conditions that make you really sweat.

Why is it so Important to Stay Hydrated When Playing Sport?

The loss of water and electrolytes from the body has a few negatives but most notable is the decrease in blood volume and resultant reduction in oxygen transport resources. Just 1-3% dehydration has been shown to have a negative impact on exercise performance.

This is a major challenge especially in sports where it’s hard to drink a lot because you’re working hard or you don’t have a free hand, such as in team sports, sailing, distance running, road cycling, etc. To overcome this the athletes need to have a strategy in place to stay hydrated during the event, especially if the competition extends over multiple days

How much/when: drink 125mls every 15 mins (500ml/hr)… or more if able.

What: A cool 6% Carbohydrate Solution with Sodium & Potassium.

The major sports drink brands have products that are ideal for athletes to drink during competition.

Also, sip some cool (16 deg C/ 60 deg F) sports drink during your warm-up. Cooler fluids are absorbed quicker and cool the body.

Athletes in multi-day events needs to be on the lookout for signs of dehydration:

• Changes in body weight – 1kg lost in a day equals a liter of fluid lost
• Changes in quantity and color of urine - reduced output and darker stream generally indicates fluid loss
• Increased lethargy or elevated resting heart rates
• Headaches
• Difficulty in concentrating
• Increased perception of exertion

Getting Ready for Exercise in Heat & Humidity

Louise Bell, Sports Dietitian at the New South Wales Institute of Sport and to the Australian Sailing Team, has the following tips for staying hydrated in humid conditions:

• Allow the body time to acclimatise to the humid conditions – either train in a hot, humid environment; and/or arrive 7-10+ days prior to competing in these condition.
• Understand your body’s own sweat response and practice drinking strategies in a training situation. Develop a plan for yourself.
• Begin competition well-hydrated and start drinking early – small amounts of fluid more often are likely to better maintain your hydration status than going long periods with little or no fluid.
• Water may not be enough – sports drinks are a better choice in hot, humid conditions as the electrolytes assist fluid uptake and retention by the body.
• Include some salty foods as part of your recovery meal or snack (eg, Vegemite sandwich, low fat cheese, small packet of savory crackers or chips). Salt is the primary electrolyte lost in sweat and adequate intake (plus fluid!) will enhance the rehydration process in hot conditions. But you don’t need to go overboard, as most of us consume enough salt naturally in our diet without having to add salt to a meal.

Further reading: Analysis of the Beijing Olympic marathon - how small athletes gain in the heat.

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