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Exercise Induced Muscle Cramping

We have all been there.  The training is in the legs, the fuel is in the tank, the Magnesium supplement is part of the morning ritual and boom…5 km from the finish line the puff adder grabs the calf muscle. You ease off and things seem better so you lengthen the stride again but the adder is back, and this time he won’t let go.

muscle cramping

“But I was well hydrated, I never missed a station”, you say, or: “I took two SlowMags this morning”. Truth is that all counts for nought. Muscle cramping is one of the eternal mystifiers for sport scientists, trainers, dieticians and athletes alike. The cause is poorly understood and a vast compendium of theories exist as to how to avoid or treat muscle cramping.

What we do know for sure is the defining presentations of a muscle cramp. Pain. Tightness. Inability to move. They are sudden and involuntary. During a cramp the effected muscle is essentially in a state of continuous contraction owing to the repetitive firing of the unit controlling the muscle. All muscle contractions are the result of a change in electrical activity brought about by fluctuations in electrolyte concentrations. Some muscles act quicker than others but they generally all fire, contract and relax in a cycle that is repeated as long as the muscle is needed. In a cramp the electrical activity fires repeatedly at such close intervals that the muscle does not get a chance to relax. Result = Twisted Knot In Calf.

The theories of the cause of cramping can be split onto 2 general areas

  1. the dehydration and electrolyte loss theories
  2. the altered neuromuscular control theories

We are learning more and more about what does not cause cramping and theory number 1 has provided the most compelling evidence. Dehydration and electrolyte losses have not been shown to have a direct link to exercise induced muscle cramping. In controlled trials athletes who exhibit cramping, or those who have muscle cramps induced show a poor correlation to hydration status or the loss of electrolytes and this makes sense when you think about it too. The fluids and electrolytes you lose during exercise are lost from your whole body and every muscle would be exposed to a change in hydration and electrolyte status. This should mean that many or all of our muscles will cramp, as is the situation in extreme cases of dehydration and sodium loss, but instead we see that it is only the active muscles that cramp, why?? Another point is that as you sweat during exercise you lose more water than you do sodium or potassium which means as you dehydrate, even though you lose some electrolytes, your concentration of these electrolytes actually goes up, not down. As our body responds to concentrations and not absolute values then it cannot be the loss of electrolytes that have an effect.

It seems much more likely that the condition of our muscles and other regulating factors are the chief culprits in the cramping debate. The risks of developing muscle cramps are linked to family history, previous episodes of cramping during exercise, increased exercise intensity or duration, underlying muscle damage and inadequate conditioning. Some research shows a link to poor biomechanics and movement patterns that strain the muscles particularly when the strength and flexibility of opposing muscles is impaired. Starting a high intensity session with prior damage to the muscles also increases the risk of cramping which means an athletes recovery strategies can have an impact.  Interestingly there is another dietary theory that may play some role and that is one of burning protein in place of carbohydrate for energy during exercise. As carbohydrate stores run out the body utilises greater proportions of fat and protein as a fuel source. There is only one observational study that supports this notion where athletes who metabolised more protein cramped more. This is somewhat supported by the earlier cramping studies that showed supplementation with carbohydrates and electrolytes reduced cramping, but much of the weight drawn from these studies was used to support the need for electrolytes as a prevention. This reduced carbohydrate theory could also be a reason why higher intensity exercise induces more muscle cramps (personal theory). It may be a related cause or just a sign that high intensity exercise is occurring.

Anyway I should find a useful message in all of this for you. So this is it: if you struggle with cramping assess your fitness, strength and flexibility, your biomechanics and your diet around training and competition. AND don’t fall for the electrolyte drink theory or  magnesium supplement advertising. What is the best way to get rid of cramping? Stretch it out and rest. Or apparently pinching your lip will work too..


*Exercise induced cramping is a different presentation to other causes of cramping that are medical in nature

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4 Responses to Exercise Induced Muscle Cramping

  1. Dirkus Apr 15, 2013 at 10:27 pm #

    What about cramping that occurs after exercise (when in a relaxed state)? Surely there must be a link to hydration and particularly electrolyte levels in such cases. If so, is that not also “exercise induced”?

    • Food For Sport Apr 16, 2013 at 9:37 am #

      Yes Dirk, the time period after exercise is included in the exercise induced definition in most studies. The greater likelihood is that this cramping is linked to the failure of neuromuscular control and not dehydration or electrolyte loss.

  2. Justin Lockhart Jul 2, 2014 at 10:14 am #

    AD, fully agree with the family history and previous cramping episodes as reasons for cramping. My dad cramped on every comrades he did, I have cramped throughout playing rugby and find myself cramping on every marathon I do, specifically on the calves and my ( short ) hamstrings! Once a muscle is used to cramping it makes it more prone to cramp in the future..Although I feel my conditioning should be enough ( 100 + km per week ) perhaps it is the recovery and nutrition prior to races I should concentrate on? I have tried different supplements and nutrition on races and fully agree, this is not a solution or the cause.

    • Food For Sport Jul 2, 2014 at 10:30 am #

      Definitely, I think the root of it is fatigue which itself is multi-factorial. There are possibilities that the role of both central and peripheral fatigue impact cramping occurrence. Sleep, general nutrition, over training, recovery, fitness, muscle length etc etc could all be influencers and different causes for different people.