DEFINITION--Profound muscle weakness following hard or unaccustomed exercise.
SIGNS & SYMPTOMS
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.
CAUSES & RISK FACTORSDecreased 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
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
Your own observation of symptoms and signs.
Medical history and exam by a doctor.
Blood studies (sometimes) to measure potassium levels.
Electromyography (See Glossary).
SURGERYNone useful nor necessary for this disorder.
NORMAL COURSE OF ILLNESSCurable and preventable without long-lasting complications by modifying the exercise program, taking potassium supplements, and avoiding dehydration.
Permanently weakened muscle groups (rare).
Fear of recurrence, resulting in unwarranted abandonment of the exercise program.
HOW TO TREAT
NOTE -- Follow your doctor's instructions. These instructions are supplemental.
MEDICAL TREATMENTMust be individualized according to the underlying disorder.
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.
MEDICATIONYour doctor may prescribe potassium supplements for muscle weakness.
ACTIVITYIf exercise-induced muscle weakness is a recurrent problem, it may be necessary to cut back on your activity level permanently.
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
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.