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Exploring Causes of Exercise Associated Muscle Cramps: Part III

Adding to the growing evidence that exercise associated muscle cramps are unrelated to hydration status and electrolyte balance….

See also, Part I and Part II

A recent study by Braulick (2012) was one of the first (if not THE first) to experimentally test the relationship between cramps and hydration in moderate and seriously dehydrated subjects.  Much of the previous literature on moderate and serious dehydration has come from actual competitions/races, which makes controlling variables nearly impossible.  Then, of course, we also have anecdotal evidence and “evidence” from sports-drink marketing.  Previous experimental literature had focused only on mild dehydration, perhaps due to health concerns in forcing dehydration (or maybe it’s tough to find willing volunteers?).

In this experiment, subjects performed an upper body ergometer/cycle task to induce dehydration via sweating.  Authors measured threshold frequency (at what muscle electricity level cramps would ensue), cramp intensity, and EMG amplitude.  Results showed that serious dehydration altered NONE of the measures studied.  In other words, cramping was unrelated to hydration status.  Conclusion:  "Significant and serious hypohydration with moderate electrolyte losses does not alter cramp susceptibility when fatigue and exercise intensity are controlled. Neuromuscular control may be more important in the onset of muscle cramps than dehydration or electrolyte losses."

Implications: These results simply indicate that hydration and cramping are unrelated, contrary to conventional wisdom. Now, some may go to the other extreme and conclude this study invalidates the need for ample hydration and a steady electrolyte balance, but in my opinion that conclusion goes too far, especially given the evidence that hydration is critical for many other functions.   Despite the evidence in this study, there may indeed by an indirect connection between hydration and cramps if hydration is shown to affect neuromuscular control.  Even if dehydration doesn’t directly cause cramps, it may indirectly affect the outcome by impairing the factors that DO directly cause cramps.  That’s only a hypothesis, but one worth considering… 

As a side note, a fairly straightforward result like this is often a telling barometer of how someone responds to evidence. 

  • accept the evidence at face value and look no further (concluding no connection between hydration and cramps);
  • accept the evidence but question whether there may be another relation via indirect mechanisms (speculation, but still possible and a valid question worth asking);  
  • reject the evidence out of pure belief (a stubborn refusal to acknowledge that you may have been doing something wrong in the past). 

In fairness, the literature in this area is limited in quantity, but overall has been consistent in result.  Despite the consistency, more research is needed to examine these effects in different tasks and in different populations.  

Reference

Braulick KW, Miller KC, Albrecht JM, Tucker JM, Deal JE.  Significant and serious dehydration does not affect skeletal muscle cramp threshold frequency.  Br J Sports Med. 2012 Dec 6. [Epub ahead of print]

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