Wednesday, March 7, 2007

A Visit from Our Resident Science Geek

Know Your Sweat Rate!!!

This week I am sharing the most important nutrition or hydration tip I can think of. Those of you who know me know I struggle with this aspect of racing more than any other. Knowing your sweat rate and using that knowledge to properly hydrate while training and racing can make a huge difference in your exercise performance. As little as 2% body loss through sweat can cause fatigue and reduce physical and mental skills.

Jim looks happy, doesn't he? It's because he KNOWS HIS SWEAT RATE and has prepped for the enormous amount of fluid he's going to lose over the 7 hours of the Steelhead Half Ironman. Read on to find out more. And no, we don't have any photos of Jim looking dehydrated and pasty. Or barfing.

Determining your sweat rate is very simple. Weigh yourself before you go out for a training session, keep track of how much fluid you consume during the workout, and then weigh yourself afterwards.

- If you have lost weight it is a result of sweat loss. Drink 20-24 ounces of fluid for each pound lost.
- If you have gained weight, drink less the next time you work out – Excessive over hydrating can be dangerous.

A good place to start is 1 liter per hour, optimally about 8 ounces every 15 minutes.

Obviously your hydration needs change depending on the conditions you are in. In the heat and humidity you will sweat more and need to take in more fluid. A great way to dial in your hydration needs is to record your change in weight during a variety of weather conditions. Over time you will see how your own needs change based on the conditions of your bout of exercise.

Sweat rates vary greatly among individual athletes; your teammate may only need 1 liter per hour on a hot day while you may need 2 or more (I have heard of athletes with sweat rates approaching 4 liters or more per hour in hot conditions).

If you are like me and have a high sweat rate, don’t despair: You can train your body to be able to handle the extra fluid intake – just like training your muscles and cardiovascular system. As you train, concentrate on gradually increasing the amount of fluid you take in per hour until you reach your optimal fluid intake.

Adventure racers have a unique challenge regarding hydration, we need to carry or find our fluids in a timely manner on the course. Knowing your sweat rate and potential weather conditions can help you plan accordingly.

Electrolytes are another important aspect of hydration which I will address in the future.

Happy training!


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