Obviously the triathlon event least affected by the summer heat is the swimming portion. Fewer things feel nicer in hot weather than being immersed in water. But running or riding a bicycle in hot, humid weather can sap the strength out of even the fittest athlete. There are a number of bad things that can happen to your body when it becomes overheated, but most of them are caused by dehydration, the loss of bodily fluids as you work out.
Your body needs fluids in order to function. The blood that pumps through your heart is a fluid and each of the trillions of cells in your body contains a little miniature ocean where most of the activity takes place that keeps you healthy and alive. It doesn't take much loss of fluid from your body before it stops running at peak efficiency. Fluids help keep your body cool and free from overheating. They keep your brain, muscles and nervous system operating at their peak efficiency, too. They even lubricate your joints so that you can move freely.
If you start to dehydrate, you'll notice troubling symptoms: You may experience cramps in your muscles. These are caused by the loss of electrolytes -- substances such as sodium (a component of salt), calcium and potassium that regulate your muscles and nervous system. As you lose electrolytes your muscles will become weaker and begin to contract involuntarily. These cramps are especially likely to strike your calves, where much of the important muscle activity in a triathlon takes place.
If you don't stop and rest (or take some of the precautions we suggest on the next page), you'll pass into a state of heat exhaustion. A warning sign of heat exhaustion is that you'll start feeling chills despite the hot weather. Then you may become dizzy and develop a headache. You might even become nauseous.
This is the point where you're in danger of heat stroke. Believe us when we tell you that you don't want this to happen. Your internal temperature will shoot up, possibly as high as 105 degrees Fahrenheit (40.5 degrees Celsius), even though you really don't have a fever. It's just your body's inability to get rid of the heat as quickly as it's building up inside you. Your brain will literally start to cook. You can become confused, go into a seizure or even lose consciousness completely. If you don't do something about it fast, heat stroke can be fatal.
But what should you do? Good question. And because you asked, the next page contains a number of ways in which you can keep your hot weather triathlon workouts safe without sacrificing your training schedule.