Muscle Cramping

Short of an emergency phone call, there’s few worse ways to be awakened in the middle of the night than a muscle cramp.  When it happens, someone usually offers the sage advice of eating bananas and drinking water.  But are you really dehydrated and electrolyte deficient in the middle of the night?  We owe this perception to early observations of miners and athletes working under hot and sweaty conditions, leading experts to believe that heat, poor hydration and electrolyte loss explained the incapacitating cramps often seen in athletes during and after exercise.  However, while this belief is still common, it is largely supported by only anecdotal evidence and lacks scientific basis.

To get to the bottom of the cramping question, researchers looked at hydration and electrolyte status before and after long and arduous events like Ironman distance triathlons or ultra running events to determine possible differences between those that experienced cramps and those that did not.  Surprisingly, there wasn’t any difference in electrolyte or hydration levels between crampers and non-crampers, indicating that some other trigger was to blame for muscle cramping.

So what’s to blame?  Well, after listening to athletes complain about muscle cramps after intensive training and racing, researchers stumbled upon a different reason to possibly explain painful muscle cramps – muscle fatigue.

A study published in the British Journal of Sports Medicine that followed a group of over long distance triathletes found that those athletes that either pushed themselves harder in the beginning portion of the race or competed at a pace that exceeded their “usual” pace were more likely to experience muscle cramps than those that competed at a more typical pace.  A similar study in the same journal also correlated recent injury and a history of cramping with increased risk of the problem.  Additionally, in a study of ultra-runners, those athletes that didn’t adequately rest or weren’t fully prepared for the race were again more likely to cramp during or after a long event.

These studies suggest that any factor that leads to greater fatigue increases the risk of muscle cramping as in all the above studies the groups did not differ in hydration or electrolyte levels when the muscle cramps were experienced.

More fuel for this alternate theory for muscle cramping is that the painful cramps typically only occur in muscles that are working such as the hamstrings of cyclists or calf muscles of swimmers.  If systemic dehydration or electrolyte deficiency were to blame, any muscle in the body would be equally likely to cramp.

Researchers have also observed that muscles that are on the verge of cramping display a greater baseline level of nerve activity than normal muscle.  The researchers hypothesized that the nerves responsible for inhibiting muscle cramps in working muscles are short-circuited after exhaustive exercise and stop performing their function, leading to muscle cramps.  The oft-used cure for cramping, muscle stretching, re-establishes normal function of the nerve – at least temporarily – and is often successful in relieving the cramp.

Of course, these studies can only infer the mechanism behind cramping, as direct observation of cause and effect is not yet scientifically possible – thus these results should be interpreted with caution as they simply have strongly correlated fatigue with cramping.  Maintaining hydration and electrolyte balance, especially during long distance events, is still important for performance and safety.  Just don’t expect that extra bottle of water to protect you from muscle cramps.

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Lisa Giannone

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