June 9, 1997
During the hot and humid days of summer, outdoor physical activity does not have to be postponed. Precaution and prevention should be used to avoid heat stroke, dehydration or heat exhaustion.
During physical activity, the body's temperature is capable of rising dangerously high. Therefore, our bodies have several mechanisms for cooling during exercise. Primarily, this happens through evaporation of sweat from the surface of the skin. The body also sends blood closer to the surface of the skin (causing the characteristic flushed appearance) as a mechanism for releasing heat. In a hot, humid environment it is sometimes a challenge to maintain a safe body temperature during exercise. The following tips are recommended to assure safe and beneficial summer workouts.
Adaptation
Allow your body to adjust to seasonal temperature changes. It can take between 10 and 14 days to adapt to warmer, more humid temperatures. Cut back on the intensity and duration of your workouts, pay careful attention to your body and stay in your target heart rate zone to prevent dangerous levels of exhaustion.
Clothing
Warm weather clothing should be loose fitting to allow the free circulation of air between the skin and the environment. When exercising in warm weather, dark-colored clothing should be avoided because it absorbs light and retains heat. Light-colored clothing reflects the sunlight and helps keep you cooler. Though cotton and linen are durable, they absorb moisture readily. Therefore, when exercising in the heat wear materials that have a mesh-like structure (i.e. polyester-Coolmax) and allow moisture to be whisked away from the skin.
Exercise Hours
Prevent dangerous heat-related conditions by exercising in the morning or evening to beat the most intense heat of the day. Try to avoid exercise between 11 a.m. and 2 p.m. If you must exercise during these hours, remember to stay in shaded areas and seek routes on grass or dirt rather than hot pavement.
Fluid Replacement
Drink plenty of fluids before, during and after exercise. If you are participating in an intense race or competition, increase your fluid consumption 24 hours before the event. Drink 13 to 20 oz. of cold water 10 to 20 minutes before exercising in the heat. This process does not take the place of the need for fluids for the duration of the exercise. Drink water during your activity, but note that your body can only absorb about 8 fluid ounces of cold water every 20 minutes.
Sports drinks are very popular among intense exercisers. However, these drinks do not improve performance or reduce stress to the body and are not necessary unless you are working out or playing for more than an hour. Absorption of these beverages can be slow and thus prevent you from being rehydrated quickly. Therefore, sports drinks should be diluted before consumption.
Protecting skin, eyes
An additional summer exercise concern is skin care. Wearing a hat-preferably wide-brimmed-can protect the neck and face. A sunscreen with an SPF of at least 15 is preferable. To prevent damage to the eyes, wear sunglasses that block 90 to 100 percent of the sun's UV rays.
Remember that there are other ways of beating the heat. Indoor fitness facilities, malls and your home are places in which you can maintain physical activity levels safely throughout the warm summer months.
Joel London is a graduate student in the School of Public Health. The Wellness column is coordinated by the Seretean Center for Health Promotion in the School of Public Health.