Complications

Dehydration

Everyone should drink lots of fluid during intense exercise. Thirst is often a poor indicator of dehydration in people who exercise, particularly older people. During a tough workout in a hot environment, the body can lose two liters of fluid per hour through sweat. Anyone who exercises intensively should take the following precautions:

• Drink 6 to 8 ounces of fluid about 15 minutes before a workout, and then pause regularly during exercise for more.
• Water is the best choice for replenishing body fluids. Glucose-sodium-potassium solutions, the so-called "sports drinks," that promise instant energy are apparently no better than water at improving endurance during prolonged intense running.
• Caffeinated beverages like coffee and soft drinks give short bursts of energy but can actually reduce fluid. Caffeine before a workout has been shown to temporarily raises blood pressure and reduces blood flow to inactive limbs.

Contrary to popular belief, drinking fluids will not cause cramps. Adequate hydration, in fact, helps prevent the painful involuntary muscle spasms that sometimes occur during exercise.

Hyperthermia (Overheating)

Overheating, or hyperthermia, can be a problem with strenuous exercise or when working out in hot weather. Overheating can cause mild to life-threatening conditions. Heat exhaustion, a moderate form of hyperthermia, is characterized by the following symptoms:

• Lightheadedness, nausea, headache, hyperventilation, fatigue, and loss of concentration.
• A high temperature (above 103° F), possibly accompanied by complaints of chills and clammy skin.

Individuals should rest in a cool, dry place, drink plenty of fluids, and bring down their body temperature with ice packs pressed against the skin.

Heatstroke. Heatstroke is the most dangerous complication of hyperthermia. The victim may suddenly cease sweating, after which symptoms such as altered consciousness, seizures, and even coma, may quickly follow. Heat stroke is a medical emergency and requires immediate cooling of the victim in an ice-water bath or with ice packs. One study suggests that risk for serious complications from exercising in high temperatures may persist as late as the following day, even if the weather has cooled down.