Profound muscle weakness following hard or unaccustomed exercise.

SIGNS & SYMPTOMS

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• Unaccustomed exercise.
• Symptoms that appear following a period of rest after the exercise, an hour or 2 later or the next day. Frequently a high-carbohydrate meal is eaten after competition or vigorous physical exercise, followed by a night’s sleep. The muscle weakness then appears the next day.
• Weakness that begins in the legs and progresses to the arms or other muscles in the body. Disabling fatigue accompanies the muscle weakness.
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  CAUSES & RISK FACTORS

  Decreased potassium levels in the circulating blood and muscle cells. The decreased potassium levels can be brought about by any of the following:

• An underlying inherited disorder called PERIODIC PARALYSIS (See Glossary) that interferes with muscle cellular metabolism.
• Excessive exercise in hot weather with loss of water, sodium and potassium, leading to dehydration.
• Diuretic medications that cause sodium loss and excessive potassium loss through the kidneys. The sodium loss is desirable; the potassium loss is a significant undesirable side effect that may lead to major body disturbances. Customary doses of diuretics may require reduction during hot weather.
  

  HOW TO PREVENT

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• Prevent potassium loss, increase fluid intake and adjust exercise programs and medication dosages during hot weather.
• Avoid the combination of diuretic medications, alcohol and heavy exercise during exceptionally hot weather. This combination can be lethal, causing strokes and life-threatening episodes of irregular heart rhythms.
• Increase potassium-rich foods in your diet.
• Take potassium supplements (with a doctor’s prescription) prior to vigorous exercise if you have had an exercise-induced muscle weakness in the past.
• Modify activity level to one below that which triggers attacks.
  

  WHAT TO EXPECT

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  DIAGNOSTIC MEASURES

• Your own observation of symptoms and signs.
• Medical history and exam by a doctor.
• Blood studies (sometimes) to measure potassium levels.
• Electromyography (See Glossary).
  

  SURGERY

  None useful nor necessary for this disorder.

  NORMAL COURSE OF ILLNESS

  Curable and preventable without long-lasting complications by modifying the exercise program, taking potassium supplements, and avoiding dehydration.

  COMPLICATIONS

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• Permanently weakened muscle groups (rare).
• Fear of recurrence, resulting in unwarranted abandonment of the exercise program.
  

  HOW TO TREAT

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  NOTE — Follow your doctor’s instructions. These instructions are supplemental.

  MEDICAL TREATMENT

  Must be individualized according to the underlying disorder.

  HOME TREATMENT

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• Replace lost potassium with supplements or increase high-potassium foods in the diet.
• Replace fluid loss with water instead of soft drinks.
• After vigorous exercise, avoid a high- carbohydrate meal.
  

  MEDICATION

  Your doctor may prescribe potassium supplements for muscle weakness.

  ACTIVITY

  If exercise-induced muscle weakness is a recurrent problem, it may be necessary to cut back on your activity level permanently.

  DIET

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• If you have a potassium deficiency, eat foods high in potassium, such as dried apricots, whole-grain cereal (hot or cold), dried lentils, dried peaches, bananas, peanuts, citrus fruits or fresh vegetables.
• Following a diet high in complex carbohydrates makes good nutritional sense to all those hoping to maintain or reach a good level of health and fitness. However, do not eat such a meal within 3 to 5 hours before competition, and eat only lightly directly afterwards.
  

  CALL YOUR DOCTOR IF

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• You have persistent or recurrent muscle weakness following exercise.
• You develop new symptoms after starting any prescribed medicine. All effective medicines have potentially undesirable side effects. These can frequently be controlled by modifying the dosage.