Beat the Heat

by Joe Cieszynski of Wenzel Coaching

Anyone who has raced Superweek in Wisconsin knows firsthand how the heat and humidity of a typical Midwest summer can make any training session or race miserable, unproductive, or even downright life threatening. Like many other parts of the country, the weather conditions here in the upper Midwest can be trying for any endurance athlete; but by understanding the underlying challenges that heat poses to the body and utilizing some practical tips, your summer racing can be both safe and successful.

In hot and humid conditions performance is limited by hyperthermia and dehydration, which can lead to heat illnesses. Several studies have suggested that the overall limiting factor to exercise capacity in the heat is core body temperature.¹  Hyperthermia is basically an increase in body temperature above normal values. Research has also found that at a core temperature of about 103 degrees the motivational drive to exercise is so reduced that we stop. Several other studies have also supported this notion.

There are three ways in which hyperthermia reduces exercise performance:

1. Perception of fatigue increases, which may be related to either increased cardiovascular strain and heart rate or increases in body temperature, or possibly both.
2. Endurance exercise capacity (time to fatigue) is reduced, yet there is very little change in maximal strength and power.
3. Metabolism is shifted from aerobic mechanisms toward anaerobic mechanisms, resulting in an increased rate of muscle and liver glycogen depletion. This is particularly important in events lasting 2 hours or more.

Dehydration: One of the body’s primary defenses against heat is sweating. Sweat rates vary from person to person and can range up to 2 to 2.5 liters an hour for well trained athletes. It only takes a 1 to 2% loss of body weight to have a dramatic effect on endurance performance. When one takes into account the maximum gastric emptying rate of .8 to 1.2 liters an hour you can see there will be a net loss of fluid leading to potential trouble.

Heat Illnesses. Athletes run the risk of developing a heat illness if they do not acclimatize themselves and use correct strategies to combat the heat and delay or prevent hyperthermia and dehydration. These illnesses include heat exhaustion, heat cramps, heat rash, and eventually heat stroke -- a life threatening condition.

Performing safely in hot and humid conditions is possible by following the guidelines below:

1. Acclimatize! It takes generally 10-21 days to acclimatize to adverse conditions. Start with shorter, more intense workouts then gradually increase your time spent in the heat. Regular, prolonged exposure to heat causes increases in plasma volume, delaying dehydration and maintaining blood supply and improved cooling efficiency through more uniform sweating. Heat acclimatization requires that you be warm enough to be sweating a little most of the time. Riding in heat and then returning to an air-conditioned building will not cause acclimatization. Your body needs to think that you live someplace hot, so get in the habit of wearing long sleeves, long pants and a hat anytime you are anywhere cooler than where you will race.

2. Hydrate, Hydrate, Hydrate! Start drinking water or a sports drink well before the race or training session and keep drinking during and after it. Check your urine color to determine your hydration status. You want your urine to look like lemonade not apple juice.

3. Pick cooler times of the day such as the morning or evening for training sessions when you have to train in the heat day after day. At least then you may not end up training in uncomfortable temperatures for your entire ride.

4. On hot training rides, measure your weight before and after. If you lose about 1 pound you are drinking the right amount. If you lose more, drink more on your next ride and try to keep track of how much you need to drink on how long a ride in what temperature so you know how much you'll need in future rides. Remember that you'll need about one more small bottle per hour in a race than in the same length training ride.

5. Apply sunscreen, the higher the Sun Protection Factor the better (SPF 30 or better). Also use sunscreen that is sweat proof.

6. Make sure to have a friend, teammate, coach or family member help work the “feed zones” during a road or MTB race. Keep drinks in a cooler with ice to keep drinks cold.

7. Carry as much fluid as you can during the ride or race. Hydration packs are great for training rides or MTB races.

8. Wear light colored, evaporative cycling gear that has long or full zippers for ventilation.

9. Pick a good helmet with plenty of ventilation. Most helmets these days have been shown to cool the head better than not wearing a helmet.

10. Be sure to wear gloves with a terry cloth backside to wipe the sweat from your face and keep hands from slipping on the bars.

11. Always keep one bottle with just water in it to dump over your head to help with the cooling process. Water on the surface of your body is more effective than water in your gut for keeping you cool. Floyd Landis went through something like 50 bottles during one mountain stage in last years Tour de France. Freeze bottles the night before your ride when possible.

12. Mix your sports drink at partial strength or drink some sports drink and some plain water. You don't need and can't absorb as much sugar with all the water you need on a really hot day. (That's why you feel bloated when you drink sports drink only and at full strength on hot days... and if you do drink sports drink only and at full strength on hot days and you don't get bloated you probably need more water).

13. Shorten the warm up. Don't use the whole 60 minute warm up on hot days that you normally use on cooler days unless you can find a cool place to do it (in a store or school for instance). Otherwise, doing the full warm up on a trainer will have you overheated before you start. Instead, get your stuff organized and get dressed and then sit in an air-conditioned car until about 25 minutes before the race. Then roll around pretty easy for 20 minutes, with just a few jumps at the end and go to the line with wetted clothes and hair.

14. Electrolyte needs vary a lot from rider to rider, but the hotter it gets the more people need to specifically supplement electrolyte consumption. If you have no trouble in the heat, don't worry about this, but if you suffer a lot, get yourself some electrolyte supplements and use them according to the directions.

15. Be sure to cool down for 10-20 minutes after a race.

16. Finally, eat or drink a recovery beverage ASAP after the race to begin the recovery process and restore lost electrolytes and nutrients.

I hope these tips help you beat the heat. Good Luck and keep the rubber down!

Coach Joe Cieszynski

1. Nielsen et al (1997), Acute and adaptive responses in humans to exercise in a warm, humid environment, Pflugers Arch. 1997 May;434(1):49-56