Exercise smarter in summer: take precautions against heat stroke and breathing problems when you work out outdoors.

Undaunted by the dog days of summer and want to keep exercising outdoors? Be aware that rising temperatures and humidity bring an increased risk for heat stroke and pollution-related breathing problems. Exercising smarter and taking precautions can lessen your chances of experiencing a heat-related injury.

"Heat-related injuries can range from a relatively minor problem like heat cramps to a more serious condition like heat stroke, which can be fatal," warns Neal Flomenbaum, MD, chief of emergency medicine at New York-Presbyterian Hospital-Weill Cornell Medical Center. Even if you're not exerting yourself, just being outdoors in the high heat and humidity can increase your risk of problems, including muscle cramps due to loss of water and salt through perspiration, headaches, nausea and weakness due to heat exhaustion. Heat stroke occurs when you can no longer perspire and your body's temperature control mechanism stops working.

It's not just the heat

It isn't just high temperatures that can cause heat stress. Humidity and direct exposure to the sun can also get you into trouble. The combination of these factors is what the weatherman refers to as the Heat Index, which measures the outside heat stress on the body. It's important to pay attention to that index when checking the weather forecast. Also pay close attention to the UV Index, which tells you how long it will take before you burn in the sun. Sunburn makes the job of heat dissipation that much more difficult.

If you can't avoid being out in the sun during peak hours--between 10 a.m. and 4 p.m.--sun protection is a must. That includes wearing a broad-brimmed hat (visors and baseball hats leave your neck exposed), and loose-fitting light clothing (it reflects sunlight and heat). Try SunGuard, a laundry additive that gives clothing a sun protection factor (SPF) of 30 that lasts for up to 20 washes.

Use a broad-spectrum sunscreen with an SPF of 30 or above. Apply sunscreen 30 minutes before going outside. Be sure to reapply every two hours, and after sweating or swimming. Use at least 1 oz (about a shot glass full) for each application.

Breathe easier