Heat cramps occur in muscles during or after exercise because sweating causes the body to lose water, salt, and other minerals (electrolytes). Leg muscles, such as the calf or thigh muscles, are usually affected most, but abdominal muscle cramps can also occur.

Signs of heat cramps include:

• Muscle twitching or spasms.
• Muscles that feel hard and lumpy.
• Tender muscles.
• Nausea and vomiting.
• Weakness and fatigue.

Heat cramps may start during the activity or up to several hours after exercise that caused heavy sweating, and they may last for several minutes. The skin is moist and cool, and the muscles are tender. Muscle twitching may occur. Fatigue, nausea, and vomiting are also common with heat cramps.

Drinking plenty of water before, during, and after activity can prevent heat cramps. This is very important when it's hot out and during intense exercise. Sports drinks are absorbed as quickly as water but also replace sugar, sodium, and other nutrients. People who are hydrated and acclimate to hot environments are less likely to experience heat cramps.

Salt tablets should not be used. They are absorbed slowly and can cause irritation of the stomach. Salt tablets do not replace water loss.