According to the American College of Emergency Physicians, in hot and humid conditions an active person can become dehydrated in just 15 minutes. Losing as little as 1.3 pounds of fluid for a 130-pound person can lead to early fatigue and increase the risk of dehydration.

The symptoms of dehydration include:

• Dry lips and tongue
• Apathy and lack of energy
• Muscle cramping
• Bright-colored or dark urine

If left untreated, dehydration can escalate to heat exhaustion or heat stroke that can be deadly. The main symptoms for these include:

• Fatigue
• Dizziness
• Nausea or vomiting
• Headache
• Rapid and shallow breathing
• High temperature
• Rapid heart beat
• Decreased alertness or complete loss of consciousness

If you experience these symptoms, doctors say you should stop activity immediately and cool down in the shade or an air-conditioned building. It's important to drink fluids to help quickly replenish what you've lost through sweat.

Some tips to prevent dehydration and other heat-related illnesses include:

• Drink water before, during and after exercise.
• If you exercise for more than an hour, have a sports drink.
• Avoid caffeinated beverages and alcohol – these fluids dehydrate the body.
• Avoid carbonated beverages, which can cause bloating and keep you from drinking enough fluid to rehydrate.
• Wear light colored, absorbent, loose fitting clothing.
• Stay in cool, shaded areas when possible.

Related information Fitness basics