Other than cars, the greatest dangers to runners are heat stroke, exercise induced hyponatremia, and to a lesser degree heat exhaustion.

The symptoms of heat exhaustion are cool, clammy skin (skin covered with cold sticky moisture), headache, dizziness, extreme fatigue and nausea. Heat exhaustion is not a medical emergency, but if it is not treated, it can lead to a medical emergency.

If it is a warm day and you experience any of these symptoms you should get into the shade, drink plenty of a cool fluid containing salt and remove as much clothing as possible. When you begin to feel better, you should call someone to give you a ride to your car. If this is not possible, return to the start of your run, or some other shelter by the most direct route. Walk slowly and rest as necessary to make sure you don't over heat again.

Heat stroke is a medical emergency. The onset of heat stroke is often preceded by goose flesh. If it is a hot day and you begin to feel chills, and you look down at your arms and see goose flesh; you need to know that you are in serious danger, you need to stop exercising immediately and do everything you can to cool off. A person who is going into heat stroke will normally have stopped sweating, so they will exhibit hot, dry skin, instead of cool clammy skin as in the case of heat exhaustion. A person suffering from heat stroke will have a rapid pulse coupled with rapid and shallow breathing. In advanced stages, they may pass out.

TREATMENT FOR HEAT STROKE

Call an ambulance immediately. Get the victim out of the sun. Victims who are conscious may refuse water because heat stroke causes them to become confused and disorientated. While waiting for the ambulance cool the victim by placing cold packs, (if available) on wrists, ankles, groin, armpits and neck.

HYPONATREMIA (Water Intoxication)

Exercise-induced hyponatremia can also be a medical emergency. Worse yet, few coaches and athletes are even aware that it exists. Hyponatremia has been only rarely seen in races completed in four hours or less; it is more commonly encountered in races requiring more than eight hours to complete, such as the Ironman Triathlon in Hawaii and the Western States 100 Mile Endurance Run in Northern California. The condition is most frequently found when athletes are exercising at a high intensity in high temperature and humidity conditions. The consensus of opinion among medical experts is that hyponatremia develops as a result of large sweat and urine sodium losses, coupled with the ingestion of large volumes of sodium free fluids. The symptoms of hyponatremia vary with how fast and far the sodium levels fall in the athlete's blood. Symptoms may be mild and nonspecific, such as fatigue, malaise, and nausea. Symptoms of moderate severity include headache, confusion, restlessness, disorientation, and slurred speech; such symptoms may reflect early cerebral edema. In more severe cases, the symptoms may include seizures, agitation, stupor, coma, pulmonary edema, and death. When hyponatremia occurs, it normally occurs after an athlete has been drinking large volumes of plain water or another dilute liquid for many hours, probably for at least 4-6 hours. The condition sometimes develops after a race in cases where the athlete has continued drinking dilute fluids in large quantities during the post-race period. The excessive emphasis that is being put on drinking fluids at warm weather races is making some athletes more susceptible to hyponatremia.

Call an ambulance immediately. Get the victim out of the sun. Do not give the victim water or any other dilute fluid, as this will only make the condition worse. Since most athletes suffering from hyponatremia are also dehydrated, if you have salt, two teaspons of salt thoroughtly mixed in a bike bottle of water, juice or ice tea, will be beneficial. If the victim is conscious and willing to eat, feed them potato chips, pretzels or any other salty food you may have available. The key is to reestablish their sodium balance, while replacing lost fluids.

HOW TO AVOID HEAT RELATED PROBLEMS

Healthy people are capable of running races in temperatures well above 100 degrees Fahrenheit, but they need to be very fit and know what they are doing. Heat stroke and heat exhaustion are brought on by heat buildup in the core of your body and are the result of metabolic and environmental temperature extremes. Even under relatively mild conditions it is possible for a runner's core temperature to rise to 105 degrees while racing.

The first key to avoiding heat related problems is found in slowing down. When you run slower, you generate less heat and therefore you don't need to sweat as much to stay cool. The second key is to drink reasonable quantities of fluids containing salt. In warm weather you should drink a minimum of four to six ounces every 20 minutes, but never more than a quart per hour (as is explained in detail below). Since aid stations are not always conveniently located along the course, it is a good idea to purchase a "Walk Bottle" (A bike bottle with a Velcro strap on it that makes carrying the bottle infinitely easier.) or a small fanny pack which is designed to carry one or two bike bottles. Such packs also have pockets which make them convenient to store your keys and a "Power Bar" or some other nutritious snack.

A runner can easily sweat more than two quarts per hour in warm weather, but laboratory studies have shown that the maximum absorption rates of water from our stomachs to our blood stream is only about one quart per hour. This is 8 ounces every 15 minutes. Fluids that are not absorbed into our blood pass into the intestine. Once you have fluid retention in your intestine, hyponatremia can develop.

An average runner will take between four and six hours to finish the marathon. If it is warm and humid and this runner is sweating at the rate of one and a half quarts per hour, he or she will lose between 6 and 8 quarts of sweat (4 or 6 hours times 1.5 quarts) covering those 26 miles. 6 quarts is approximately 12 pounds or about 8% of a 150 pound runner's body weight. This fluid loss is sufficient to bring on heat cramps, heat exhaustion and even heat stroke. However, if this runner consumes and absorbs a saline solution at the rate of 1 quart per hour, he or she will reduce his or her losses to only 2 quarts. 2 quarts is approximately 4 pounds or less than 3% of a 150 pound runner's body weight. This loss is significant, but it should not cause any real problems for a healthy athlete. If the runner, in the above example, were to consume 1.5 quarts per hour of plain water (6 quarts in 4 hours) he or she would again replace as much as 4 quarts of the fluid lost in sweat (remember your blood stream can only absorb approximately 1 quart of fluid per hour) and as in the case cited above, he or she will still be dehydrated. The 2 quarts the runner drank that were not absorbed into the blood stream would have passed into the intestine and now that runner has a mild risk of developing hyponatremia. So your best strategy when running in warm weather is to drink as much fluid as you are losing in sweat, but never more that one quart per hour.

WHAT IS YOUR SWEAT RATE?

In order to know how much fluid to drink, it is helpful to know your sweat rate. Sweat rates vary dramatically among people of the same height and weight. To learn your sweat rate for a given temperature and exercise level. Get well hydrated. Take your nude body weight (nude weight is best so the effect of dry and wet clothing and shoes aren't a factor), dress and go out for a one hour run. Do not eat or drink anything during this hour. As soon as you return home, strip and take your nude body weight again. Since we only burn 100 calories per mile, and it takes 3600 calories to make a pound, most of the weight lost will represent your water lost through sweating. If you do this before and after runs of different distances and under different temperature and humidity conditions, you will be better able to estimate how much you will need to drink to remain adequately hydrated for longer runs at similar temperatures, humidity and rates of effort.

You need to practice drinking while running. In order to accustom your body to absorbing fluids on the run and to aid in your recovery, you will need to drink water and your favorite fluid replacement, at least occasionally, when you run longer than seventy minutes.

Drinking during a race takes practice and is one of the most important things a marathon runner must learn to do. Practice drinking during training runs and in one or more training races. This will give you experience with the way fluids are provided in races. (If you participate in practice races, be sure to properly enter them and to wear your number. Running a race without entering the event is rude and unethical.)

Scientific research has shown that the most effective way to keep your body hydrated in marathons is to begin by drinking between 16 and 20 ounces of fluid immediately before you start running and then drinking from 5 to 10 ounces every twenty minutes thereafter. The research has shown that fluid is absorbed more rapidly when your stomach is full, so you must drink the initial 16 to 20 ounces of fluid to fill your stomach. The research has further shown that with a full stomach, the body can absorb between 25 and 35 ounces of fluid per hour. However, sweat rates in a marathon can easily exceed 70 ounces per hour. Fortunately, you don't need to replenish all the fluids you lose, because for example, a fully hydrated 150 pound person could lose as much as 96 ounces (3 quarts) of fluid, before their performance would be seriously affected.

Copyright © 2001 by John Loeschhorn - Mail to:mtnrnr@pacbell.net
April 1, 2001