Stay Hydrated to Exercise Safely in the Heat

The summer heat can take a toll on the body during outdoor exercise.  Excessive heat warnings may be common May through September but do not wait until the weather man issues the heat warning to be cautious about overexertion while outdoors during this time of year.  Anytime that the day time heat exceeds 90 degrees Fahrenheit it is time to use caution when exercising or working outdoors.  This is especially true anytime that a person lives in a place of high humidity like Arkansas.  The increased heat index associated with humidity puts people that live in hot, humid environments at a greater risk than those who live in dry heat.

For the person exercising outside this time of year the excessive heat is not the primary concern. Given enough time, the body can adapt to a hot humid environment provided that it can stay adequately hydrated. This may be done over a period of three to four weeks with gradual increases in both length of time training and intensity of exercise in the heat. It is the increased risk for dehydration as the body loses water through excessive sweating that may lead to a potential exercise-induced heat-related medical emergency.  Staying hydrated is a key component for staying safe in the heat. Proper hydration begins long before the workout or practices does.

Most people wake up dehydrated in the morning. The several hours of sleep that a person should be

getting are also several hours during which the body is not being hydrated. That first trip to the toilet is more about eliminating certain biochemical waste products than it is about eliminating excess fluids. However, it is the first opportunity to assess hydration status. At all times of the day, urine should be the color of clear lemonade, just a shade darker than water. If it is bright yellow the body is dehydrated. If the urine is both yellow and has a strong odor the body is severely dehydrated and is dire need of fluids before any physical activity. Working outdoors or exercising in the heat and being dehydrated from the get go is asking for trouble. But trouble may be avoided if the body is properly hydrated for the activity ahead.

Sweating is a natural method for the body to cool itself during physical exertion.  In addition to some of the chemical waste products that the body produces during exercise, sweat also helps to release the excess body heat generated by the exercise, thus cooling the body. The problem comes when the body has sweated off too much excess water causing a state of dehydration.  When this happens the body is unable to release enough excess heat through sweating because it lacks enough water to produce sweat.  As the sweating mechanisms stop working the the resulting rise in body temperature may become too high. This has the potential to cause severe damage both to the brain and the body, up to the point of death.  This can happen when the body loss of as little as 1% of body weight will result in a rise in body temperature.  For a person that weighs 150 lbs this is a water weight loss of 1.5 lbs. Fluid loss in the range of 3-5%, 4.5 to 7.5 lbs, will place a great strain on the cardiovascular system; a dangerous decrease in blood pressure combined with an excessively increased heart rate. As blood pressure begins to drop the heart must beat faster in order to circulate the blood to keep the body going. Staying hydrated replaces fluids, preventing this dangerous drop in BP. Go for an hour run during the day time high and this can be done quite easily. At a 7% loss, 10.5 lbs for a 150 lb person, complete collapse of the body is likely. This is exercise-induced heat stroke and a medical emergency. When it sweats, the body also loses electrolytes, primarily sodium and potassium. This is why sports drinks like Gatorade may be necessary of exercise will last longer than one hour.

Here are some safety tips to reduce the risk of putting yourself in danger.

·         Avoid exercising in the heat of the day.  Exercise early in the morning or late at night.  Exertion during the coolest temperatures of the day will minimize the risk of a heat-related problem.
·         Stay hydrated all day.  Do not drink simply because you feel thirsty.  Remember, the most accurate assessment of proper hydration is the color of urine. If you plan on exercising in the heat drink at least one ounce of water per pound of body weight per day to ensure proper hydration.
·         Weigh yourself before and after exercising outdoors. For every pound of water lost from exercise drink 12 oz of water and 8 oz of an electrolyte sports drink. Water alone is inadequate because it does not contain the electrolytes that help regulate blood pressure to safe and healthy levels. Try to be completely re-hydrated within 2-3 hours after finishing exercise. 
·         Do not go to sleep at night dehydrated from a long run in the heat. This will severely impair the recovery process. It is better to wake up to use the bathroom at night than to sleep all night dehydrated. A decrease in the frequency of urination combined with prolonged heat exposure is a symptom of dehydration. 
·         Exercise with a partner and carry a cell phone; if one of you has a problem the other person can call an ambulance.
·         After finishing the exercise focus on rehydrating and cooling off before taking a shower. The temperature change shock of going from exercising in the heat to cool indoors with a/c to a hot shower may make a person feel worse if they have not rehydrated. Wait 20-30 minutes and start rehydrating before cleaning up.