Exercise Associated Muscle Cramps

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Exercise associated muscle cramps (EAMC) are skeletal muscle cramps that occur without an underlying metabolic, neurological, or endocrine pathology (1).

What causes EAMC?

The answer may very well be in the question…exercise. But let’s delve a little deeper. In a 2010 paper out of Sports Health by Miller et al., the authors point out that there is no one definitive cause of EAMC, but a couple of proposed theories as to why they occur.

Dehydration/electrolyte imbalance

EAMC are said to occur as the result of fluid and electrolyte imbalance that typically occurs with exercise. This makes sense when thinking about exercising in hot/humid environments. I know for me personally, I’ve always associated muscle cramps to with sweating a lot, which tends to happen when I’m in a hot/humid environment. However, a prospective cohort study out of the British Journal of Sports Medicine in 2010 looked at 210 Ironman triathletes to identify risk factors for EAMC and found that the factors consistent with the development of EAMC were competing at a fast pace and previous history of EAMC, NOT serum electrolyte concentration and body weight, potentially suggesting that fluid/electrolyte imbalance is not a cause of EAMC (2). Now this is just one study looking at fluid/electrolytes and until there is more quality research on this area I wouldn’t go so far as to say that fluid/electrolytes have nothing to do with EAMC, but the results of the study are interesting to say the least!

A few other things to point out is that the fluid/electrolyte theory is also limited because it does not explain the reason that EAMC occur when exercising in a cold environment (1). Lastly, while I’ll go more in depth on this below, this theory would also not explain why stretching immediately relieves EAMC (1).

Neuromuscular

WARNING: it’s about to get real sciency for a minute! Taking a step back in time to undergrad exercise physiology for this explanation!

This theory proposes that neuromuscular fatigue causes an imbalance between impulses from the muscle spindles and the Golgi tendon organs within the muscle-tendon complex (1). The muscle spindles (located in the muscle belly) respond to a quick stretch of the muscle and result in a contraction within the muscle-tendon complex. The Golgi tendon organs (located in the musculotendinous junction) respond to tension of the muscle tendon and result in inhibition (relaxation) of the muscle-tendon complex. Click HERE and HERE for videos further explaining this.

It is important to point out that the EAMC tend to occur when a muscle is contracting in a shortened position (1). Because we know that the Golgi tendon organs respond to tension of the muscle tendon, if this tension is not occurring because the muscle is contracting in a shortened position, the inhibitory impulse that the Golgi tendon organ would normally produce is decreased. This would explain why stretching works to decrease EAMC; stretching increases tension in the muscle tendon, which activates the Golgi tendon organs, and results in inhibition of the muscle-tendon complex.

There are some limitations to this theory as well, which Miller et al. 2010 cover more in depth. With no one theory proven to be correct, it is perhaps more likely that EAMC occur due to a combination of factors. This brings us to treatment of EAMC.

What is the best treatment for EAMC?

Your first reaction might be something like this:

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But let’s go back to the theoretical causes of EAMC. If the cause of the cramps is indeed a fluid/electrolyte imbalance then it is true that replenishing fluid with electrolytes could certainly help. However, if the cause is neuromuscular in origin, then replenishing with fluid will only get us so far and thus maybe we should consider stretching as a treatment. Here’s my two cents: since there is no definitive cause I say why not replenish fluids and stretch? In my limited first hand experience of treating cramps in athletes post half marathon/marathon I have to say that static stretching applied to the muscle in question is definitely effective in reducing the cramps; however, when the cramps become more severe and span several body parts simultaneously is when I think the athlete should be monitored more closely to ensure their current physiological status is not declining.

How can we prevent EAMC from occurring?

Miller et al. 2010 state that maintaining adequate hydration and electrolyte levels are a good prevention strategy for EAMC (1). The authors also add that the National Athletic Trainer’s Association’s recommendation for athletes prone to cramping is to add 0.3 to 0.7 g/L of salt to their drinks (1). As far as neuromuscular theory is concerned, it would certainly be plausible that targeting the muscle spindles and Golgi tendon organs through plyometric exercise could have potential benefit.

As you can see there is still much to learn when it comes to EAMC, but hopefully this gives you a good background knowledge on what cramps are, why they occur, and what we can do to treat and potentially prevent them!

Until next time, don’t let exercise ‘cramp’ your style 😉

Aimee

Sources

  1. Miller KC, Stone MS, Huxel KC, Edwards JE. Exercise-associated muscle cramps: causes, treatment, and prevention. Sports Health. 2010;2(4):279-83.
  2. Schwellnus MP, Drew N, Collins M. Increased running speed and previous cramps rather than dehydration or serum sodium changes predict exercise-associated muscle cramping: a prospective cohort study in 210 Ironman triathletes. Br J Sports Med. 2011;45(8):650-6.

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