Running In Heat and Humidity :: What To Do?

So many of us are struggling with extreme heat and humidity, I really felt compelled to do a little research to find out how best to cope with the situation. Let’s face it, training for a Half or Full Marathon is no picnic when you’re doing all those miles on a treadmill – and your iPod will only alleviate the boredom temporarily. So, how to cope?

What’s Happening In the Heat

First, it’s important to understand what happen to your body when you do strenuous exercise in the heat.

Even in relatively moderate conditions of 80 degrees (or over 70 degrees with high humidity), it is easy to become progressively dehydrated. During a hard workout or race, when your metabolic rate and heat production are high, your core temperature can increase to a hazardous level.

According to Pete Pfitzinger of Running Times Magazine, “When you run in the heat, your body has to deal with both the heat of the environment and the heat produced by your muscles. One of the body’s responses is to send more blood to your skin to enhance cooling, leaving less oxygen-rich blood available for your muscles. (that’s why you feel like you’re slogging through wet mud!) Your body also increases sweating to remove heat from your body through evaporative cooling, which makes you progressively more dehydrated. As you become dehydrated your blood volume decreases, so even less blood is available to go to your working muscles, and your heart pumps less blood per beat. This is not pretty.

“With less blood available to the working muscles and the cardiovascular system under stress, running performance is compromised. Research suggests that performance is reduced by about two to three percent for each one percent loss in body weight due to dehydration. If you lose more than about five to six percent of body weight, the risk of heat-related illness increases appreciably. The risk of heat-related illness is also increased by some prescription and over-the-counter drugs, which increase metabolism or decrease sweat rate or blood flow to the skin.”

Pfitzinger continues to say that “running on a day that is both hot and humid is even more dangerous because sweat rolls off your skin onto the ground rather than cooling you off through evaporation, due to the high moisture content of the air. You still sweat, but the sweat does not have the desired cooling effect, so heat builds up in your body and your core temperature increases. This is particularly true during races, when competition makes many runners ignore their body’s warning signals. Races of 5K to 10K in extreme heat and humidity can pose the greatest danger of overheating because your running intensity (and therefore heat production) is so high that your body cannot eliminate heat quickly enough to prevent a steady increase in core temperature. In those conditions, the best plan is to reduce your pace from the start.”

Don’t even think about trying to set a PR in this weather.

Steps To Take

Preventing Dehydration

First, ensure you are well-hydrated before workouts and races. Your body’s thirst mechanism is not a great indicator of dehydration and probably won’t get you safely through a severe weather workout. Drinking until your urine is lightly colored is a pretty good indication that you are well-hydrated. The American College of Sports Medicine recommends drinking about a pint of fluid approximately two hours before exercise to help ensure adequate hydration and to allow time to excrete excess water. Absolutely avoid beverages containing alcohol and caffeine, as they have a diuretic (makes you pee) effect.

How much fluid you lose during running depends primarily on the heat and humidity, and how far you are running. If you lose two percent or less of your body weight during a run, then you can simply rehydrate after you finish, but for longer runs, or in more extreme conditions, you should replace fluids during the run.

The amount of fluid that you should drink during the run depends on how much fluid you have lost and how quickly fluid empties from your stomach. During running, the stomach can typically empty about five to seven ounces of fluid every 15 minutes (this varies between runners). Keep in mind that during a race or hard training run, it is difficult to drink more than three to four ounces at an aid station without stopping.

Running on a hot day, you may sweat out three to four pints of fluid per hour. Since you can only drink one to two pints per hour, you are going to finish somewhat dehydrated. To calculate how much to drink after running, weigh yourself before and afterwards, and drink enough over several hours to bring your weight back to its pre-run level. Because some of the fluid you drink will be lost as urine, you will typically need to drink about one to one-and-a-half times the amount of fluid that you lost.

It is really important to re-hydrate after a hot weather run or race because dehydration will slow down recovery. Remember that body fluids help to remove waste products and bring nutrients to tissues for repair. Quickly replacing lost fluids after running, therefore, will help you to recover as quickly as possible. You definitely need a strategy not just for preventing dehydration from each run, but also for preventing cumulative dehydration over many days of hot weather running.

Hypo-What?

Hyponatremia is a decreased concentration of sodium in the blood, which can lead to brain swelling, seizures and death. Hyponatremia can occur from drinking excessive amounts of water (or other fluids with low sodium levels) before and during long-duration exercise. But don’t freak out. If you don’t drink excessively or use sports drinks or other sodium-containing drinks before and during running have a very low risk of hyponatremia.

The American College of Sports Medicine advises that, "inclusion of sodium (0.5-0.7 grams per liter of fluid) in the rehydration solution ingested during exercise lasting longer than one hour is recommended since it may be advantageous in promoting fluid retention, and possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid."

Pre-Cooling

With pre-cooling you moderately reduce your body temperature before hot weather exercise. This can be a good strategy to improve performance during hot-weather races or strenuous workouts.

If you are planning some really intense training or a long race in this weather, they actually make something called a cooling vest, which has pockets for ice or gel packs. You put on the cooling vest when you start your warm-up and wear it until shortly before you start your run. This will delay heat accumulation and reduce sweating during your warm-up.

Another cooling device is one I’ve already mentioned in another post – rolling ice cubes into a bandana and tying it around your neck. While this is not as all-over a remedy as a cooling vest, it will definitely help cool you a the ice melts and cold water trickles don your neck and chest.

Training Adjustments

To maintain the quality of your training when the summer heat is intense, run early in the morning (even just before dawn) when the temperature is lower. Run in the shade and avoid direct sunlight; run in light colored clothing and wear eye protection. You may want to wear a visor, which will keep the sun out of your eyes but still allow heat to escape from the top of your head. Be sure to tell someone where you are running and how long you expect to be gone.

On days when you can predict that you will not be able to maintain your normal pace, face reality and adjust your pace and distance accordingly. And – here it comes - when the heat and humidity are really severe, you will get a better workout by running on a treadmill in an air-conditioned gym. If you do not have access to a treadmill, do another type of indoor workout or take a day off when the heat is dangerously high.

If Trouble Strikes

If you become dizzy, nauseated, have the chills or stop sweating – STOP RUNNING IMMEDIATELY! Find some shade and immediately drink water or a fluid replacement drink. If you feel confused and/or your skin is red, hot and dry even under the armpits you may have heatstroke, which is a life-threatening condition. Seek help immediately!

These record high temperatures all across the country are truly dangerous for those of us who exercise outside, and especially for those living in high-humidity. Take proper precautions and use common sense…and just remember…fall is coming baby!

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