Avoid exhaustion, cramps and heat stroke.

Being physically active year round is a positive way to improve health and protect against heart disease, diabetes, obesity and osteoporosis. Physical activity also increases a person's sense of well-being. Exercising outdoors in warm weather can be refreshing, especially after spending months inside during a long and frigid winter. In the summer months, when it is hot, hazy, and humid, it is important to understand how to safely and effectively exercise in the heat and smog.

"Even healthy people should take it easy during extremely high temperatures or high pollution days to avoid medical emergencies, but those with respiratory illnesses, such as asthma, emphysema, and bronchitis or people with heart disease and the elderly must be especially careful," says Dr. Gaetan Tardif, Vice President of Medicine at the Toronto Rehabilitation Institute, Canada's largest provider of adult rehabilitation services.

Overdoing it can lead to heat exhaustion, fatigue, heat cramps or even heat stroke. There are a number of things one can do to avoid heat and smog-related problems while exercising in the summer.

Dr. Tardif offers these tips to reduce your risk:

• Drink plenty of fluids - preferably water before, during and after exercise. Water is absorbed by the body quicker than most other fluids, and does not contain any chemicals or agents that have a dehydrating effect.

• Exercise on cooler surfaces such as grass, dirt tracks or light coloured pavement and wear loose fitting clothing that allows sweat to evaporate.

• Check air quality reports on the weather page in your local newspaper or contact Environment Canada for air quality reports. Moderate your physical activity on 'smog alert' days by substituting vigorous activity, such as running or jogging, with moderate or light activity such as walking, relaxed bicycling, stretching or easy gardening.

• If you must exercise outdoors when pollution levels are high, avoid exercising during rush hours. Exercise prior to 10 a.m. or after 8 p.m.

• If you are on any medication, check with your doctor before exercising in the heat as some medications may hinder your body's ability to regulate its temperature.