Being outdoors in warm weather can be exhilarating, especially if you have spent months inside because of cold weather. Summer brings many opportunities to participate in physical activities and sports, as well as the daylight hours to enjoy these pursuits! However, understanding how to safely and effectively exercise in the heat is important. Here are some dos and don'ts to help guide you.

What to Avoid

• Don't exercise strenuously in high temperatures over 90 degrees Fahrenheit (F) or about 32 degrees Celsius (C) or high humidity (over 75%). It is especially important not to work out strenuously when both temperature and humidity are high. Normally the body deals with high heat levels through perspiration, but when humidity levels are also high, sweat does not evaporate as quickly and body temperature can rise to dangerous levels. (The "heat index" measures a combination of heat and humidity. This index tells you how hot it "feels.") Avoid all outdoor activities if there is a chance of thunderstorms or lightning.

• Don't participate in competitive events, such as 5K runs, during the hottest part of the day. In warmer climates, make sure you complete your runs early in the day if possible o

• Don't participate in strenuous swim workouts in heated pools during the summer. Even though you are in the water, you can still become dehydrated and overheated when swimming. For hard swim workouts, the water temperature should be 75 to 78° F ideally, and no more than 80° F (about 26.6 degrees Celsius). Make sure you drink a steady supply of liquids.

• Don't keep exercising if you feel dizzy, faint and/or nauseous. These reactions may be signs of heat exhaustion, which occurs when bodily stress from heat begins to overpower the body's capacity to regulate its temperature. If you do not rest in the shade and drink water until you recover, you risk developing heat stroke, an even more serious condition than heat exhaustion. Don't exercise when the air pollution index is high. Air pollution can damage your lungs. If your area is susceptible to smog, check the air pollution index in your local paper. A health advisory is normally issued at .15 parts per million (ppm) on the pollutant standards index. If a health advisory is issued, anyone with any type of respiratory or heart disease should stay inside until the advisory is lifted.

Successfully Exercising in the Heat

• Do exercise in the early morning or early evening (less sun, less air pollution) if possible. Try to avoid exercising between 10:00 am and 2:30 pm.

• Do drink more water than usual. A person of average weight should drink at least 12 cups of water a day while working out in the heat; an overweight individual needs even more. Children should drink about six to eight cups of water a day. Cool water is the best choice unless you exercise for periods longer than 90 minutes, in which case nutrients other than water may get depleted. Then a sports drink will help restore those nutrients to healthy levels.

• Do carry a frozen water bottle in a fanny pack or in the back of your shorts. The bottle will keep you cool, supply you with cold water (cold liquids leave your stomach faster) and even help reduce inflammation in your low back.

• Do wear loose clothing (preferably made of cotton or sweat-wicking fabric). Avoid open-mesh jerseys and tank tops; they expose you to too much sun. Light-colored clothes best reflect the sun. Wear sunblock (SPF 15 or higher), a cap or hat and sunglasses. Keep cool by wearing a wet bandana or an ice pack scarf around your neck.

• Do acclimate yourself gradually. If exercising in the heat is completely new to you, take it easy for the first two weeks.

• Do try to walk/run/bike along shaded pathways or trails. Alternately, walk/jog in malls, where it is cool and shady. Most malls are now open early for mall walkers.

• Do take special care if you are very underweight, very overweight, pregnant or an older adult. Many experts recommend you maintain a moderate intensity level--60 to 70 percent of predicted maximum heart rate--when exercising in the heat. Stay fully hydrated at all times and take many rest breaks.

Remember: You never want to sacrifice one body part for another. Going for a hard run in the very hot part of the day might be great for your legs but could damage your skin, heart and lungs. The trade-off is not worth it in the "long run." Enjoy your workout!