Although clinical research is still tentative, there appears to be at least two different causes for muscle cramps that occur during or shortly after vigorous or prolonged exercise.
Costa Rica Basketball reviews those two causes, and presents a couple of simple tips to follow in order to prevent muscle cramps caused by exercise.
The Two Main Causes of Exercise Induced Muscle Cramps:
The first cause is often called “muscle overload cramps” and occurs after unusually intense use of the selected muscle(s).
The second cause is often called “exertional heat cramps”, but more accurately should be called “whole body exchangeable sodium deficit induced muscle cramps” as it is associated with prolonged and profuse sweating with the loss of both water and salt (sodium chloride) faster than either are replaced.
In susceptible persons, either mechanism is sufficient to induce severe and competition stopping cramps. But the risk of cramping increases if there is both intense use of multiple muscle groups over prolonged periods of hours in hot conditions that stimulate excessive sweating and subsequent salt loss and dehydration. Examples of this “double jeopardy cramping risk” would be marathon races and prolonged basketball and tennis matches in hot and humid conditions.
Treatment of Acute Muscle Cramps:
As might be expected, effective treatment of whole body exchangeable sodium deficit-induced muscle cramps, involves rapid ingestion of an appropriate amount of salt and sugar water.
At the first sign of muscle twitches and over a 5 to 10 minute interval, the athlete should drink ½ liter (about 16 ounces) of a carbohydrate-electrolyte drink with 3 grams of salt added and thoroughly mixed.
Effective treatments of pure muscle overload muscle cramps include cessation of activity and passive stretching and massage of the affected cramped muscle.
In my experience, having the person “actively” stretch the cramped muscle by slowly contracting the antagonist (opposite) muscle group is more effective and less painful than having someone else forcibly stretch the cramped muscle. For example, if you have an intense cramp in your left gastrocnemius (calf) muscle, you can direct the left foot to slowly dorsiflex. In lay terms you use your mind to “tell” the left foot to slowly raise upward which will direct the front shin muscles to contract and cause the left ankle and toes to bend forward.
This activates a wonderful phenomena of “competitive inhibition” between the lower leg’s front and back muscles so when the brain tells the front lower leg muscles to contract, it simultaneously sends an equally strong signal to the back gastrocnemius (calf) muscle to relax.
Some authorities believe that applying ice to the cramping muscle regardless of cause can aid in reducing nerve irritability and thereby reducing the cramps.
For muscle overload cramps, preventive strategies include pre-exercise stretching and range-of-motion movements of the cramp-prone muscle groups and improving aerobic and muscle conditioning through progressive, incremental fitness programs.
Athletes who are still prone to overload cramps should take care to pace themselves as much at their sport will allow. For example, tennis players should take the maximal time between games and sets in tennis that the rules allow to give their muscle the maximal rest time to recovery from the “overload”.
Both from a health and a competition point of view, it is better to prevent muscle cramps than to treat them after they have begun to cause pain and adversely affected the athlete’s performance.
For whole body exchangeable sodium deficit induced muscle cramps, preventive measures focus on pro-active fluid and salt loading before the onset of sweat-inducing exercise and active maintenance during the exercise.
This could theoretically be done by putting extra table salt on one’s food and drinking extra fluids at the meal before the competition. A more accurate and controllable strategy is to drink and eat normally at the last meal and then just before starting to warm up (and at least 20 minutes before vigorous competition) to preload the body with a sugar-electrolyte drink with three-1 gram salt tablets crushed and dissolved per liter (quart).
Most young adult athletes will benefit from about ½ liter (16 ounces) of this solution, but the optimal amount will vary with the size of the athlete, their recent fluid and salt intake, the level of exercise intensity anticipated, the temperature and humidity and whether the athlete is a heavy sweater.
As soon as the athlete begins to exercise, the blood vessels will dilate and the intravascular space (the fluid in all of the arteries, capillaries and vein) will expand to allow the heart to increase cardiac output to support the vigorous exercise. So this extra salt water should be absorbed quickly. Sugar in the fluid will speed absorption of both the water molecules and the salt so it is not advisable to use pure salt water or sugar substitute “diet” drinks for fluid and salt loading).
Maintaining adequate fluid and salt level during prolonged (multiple hour) competition is extremely important because of the huge fluid and salt losses which can happen especially on hot humid days.
It has been demonstrated time and again that having athletes drink only when thirsty can result in performance robbing dehydration as the thirst mechanism is insensitive especially in the heat of competition or when athletes are chewing gum or in other way keeping their mouths wet.
If an athlete wants to know if they are well hydrated, they should “ask their kidneys”. In a healthy athlete, his/her kidneys are constantly monitoring the blood pressure and blood flow through the renal arteries and assessing if the body has too much or too little fluid. So a little experiment that any athlete can do (at least during practice) is to void completely just before drinking the above bolus of salty sugar water and beginning to warm up. Then at one-hour intervals go to the bathroom and notice whether they can urinate. If they can’t or can void only a few ounces, their kidneys are telling them that they need more fluid. If they can void a cup or more (8 oz.) each hour, they are well hydrated and can slow their intake.
Although there is a lot of “conventional wisdom” suggesting that muscle cramping comes from deficiencies of potassium, magnesium and even calcium, there is little evidence that in healthy athletes that these electrolytes are the cause. So if an athlete wants to eat a potassium rich banana before or during his competition that is fine, but it probably won’t make a difference in whether s/he gets muscle cramps.
Debilitating exercise-induced muscle cramps are caused by at least two separate, but often overlapping mechanisms. Progressive muscle conditioning fitness programs and methodically pre-competition stretching and pacing the intensity of the exercise can reduce the chances of muscle overload cramps. Strategic pre-loading with salty, sugar water shortly before and during prolonged competition especially during hot and humid conditions can reduce the chances of whole body exchangeable sodium deficit-induced muscle cramps.
Bentley, S. Exercise-induced muscle cramp. Proposed mechanisms and management. Sports Medicine 1996 Jun; 21 (6) p 409-20.
Bergeron, M.F. Muscle Cramps during Exercise – Is It Fatigue or Electrolyte Deficit? Current Sports Medicine Reports. 2008, Volume 7, Number 4. Supplement S50-55.
Miles, M.P., Clarkson, P.M. Exercise-induced muscle pain, soreness, and cramps. Journal of Sports Medicine and Physical Fitness. 1994, Sep; 34 (3), p. 203-16.