Multisport: Cooling Your Core

By: Colin Izzard, CTS Senior Coach

There are various environmental factors that lead to a diminished ability to perform in cycling and sports. A change in core temperature is one that very frequently affects athletes. Maintaining core temperature within a very small window is critical for your health and performance.

To begin with let’s look at how your body maintains core temperature in hot conditions. The hypothalamus is your body’s thermostat, and essentially controls the sweat glands. When the body senses that its temperature is rising above ideal levels, the hypothalamus jumpstarts your sweat glands. The evaporation of the sweat from the skin is your body’s primary method of cooling itself. Increasing blood flow to the skin is another cooling method your body uses. Instead of evaporating fluid to cool the skin, moving warm blood closer to the skin’s surface allow heat to radiate into the cooler environment through convection.

Having a basic understanding of how the body controls core temperature gives you a few more things to think about. Hydration, clothing, time of day for training all play important roles in controlling core temperature. As the temperature rises and the body sweats more, you have to keep a close eye on hydration levels. Loss of fluids occurs both through sweating and respiration (breathing). Athletes in dryer areas will have to take respiratory losses into account more than those in humid climates. The average sedentary person requires 1.5 liters of water a day, but athletes will need far more than this, up to a gallon or more.

When exercising it is critical to consume fluids to stay as hydrated as possible. A loss of 2% of your body weight due to dehydration can result in upwards of 45% less in your capacity to perform high intensity exercise. Further, about half of these fluids should be some sort of sports drink. Sweat will rob the body of essential electrolytes. Without replacement of these electrolytes, like sodium, the body will eventually slow down or completely shut down. Further, sports drinks containing glucose and electrolytes will help speed the absorption of the fluids in the small intestine. Experiment with different brands and flavors of sports drinks until you find one that sits well with your stomach and is palatable.

Hydration is one the keys to keeping core temperature constant. Be sure to always be well hydrated at the start of your training session, and to keep drinking throughout the workout. Try working up to being able to start a training session or event with a slightly full feeling in your stomach. Be careful to experiment with how much fluid you can consume without getting sick in training before doing it in a race.

Clothing choices also significantly influence core temperature. Generally, most modern cycling and running clothing is made of materials that wick sweat away from the body to allow for faster evaporation therefore faster cooling. One of the most important pieces of functional clothing is a base layer. The main aim with a base layer is to keep the core temperature stable. Whether the conditions are cold or warm, an undershirt is always a good thing to have on. Another good item in the heat of the summer is a full zip jersey. By having a full zipper you can really open up the front of the jersey and get some good cooling from the wind on your body. Sleeveless jerseys are also good to allow cool air and wind to rush around your underarms.

Several other considerations for regulating core temperature include time of day and sunscreens. For those living in hot climates, training should be done early in the day or later in the afternoon. That way the heat of the day can be avoided, thus allowing for cooler core temperatures and therefore higher quality training. Also, always carry some money with you for store stops. That way you can always buy a cool drink. When training in the heat and sun it is also important to use sunscreen to protect your skin. However, avoid oilier sunscreens as they can block pores and slow down your perspiration. Coppertone and Bull Frog make sun screens that are alcohol based that will last on long rides and not slow perspiration rates.

Overall, to really beat the heat of the summer remember to drink, drink, drink. Dehydration is perhaps the largest cause for lower quality training and racing in the heat. Keep in mind when you are going to train each day and try to make it when it is a little cooler out, your body will thank you for this. Have fun and don’t just train, train right!

© 2005, Carmichael Training Systems, Inc.