In my last post I provided research which refutes the age-old claim that muscle cramping during exercise is caused by electrolyte deficiency and/or dehydration. The most commonly proposed cause of cramping is a low level of sodium which came out of very poor research about 100 years ago. This myth, like the 220-minus-your-age and fat-burning-zone myths, will probably never go away. Athletes seem to be convinced. The sports drink companies have done a great job of convincing us of this. While the primary benefit you get from a sports drink during endurance exercise is carbohydrate, some of these companies have gone out of their way to sell us the salt in their product as the primary reason to buy it.
I promised in that last post that I’d get at what is the latest theory for a cause of cramping. Realize that no one (and that includes sports drink companies and scientists) knows what causes cramps. So we’re stuck with theory until someone figures it out and then it is corroborated with several follow-up studies over several years. So we are long way from knowing the cause even if a theory appears promising.
The latest theory has to do with fatigue and the nervous system, specifically muscle spindles and Golgi tendon organs. But rather than go into a long explanation of all of this physiology I’m going to refer you to a site where a pair of sport scientists explain it to you. Go here to find it. The scientists are PhDs Ross Tucker and Jonathan Dugas who studied under Dr. Timothy Noakes, author of The Lore of Running, at the University of Cape Town, which is where the theory appears to have had its origins.
I doubt if you will see a sports drink that addresses this theory. But I could be wrong. In researching this post I came across a recent study from North Dakota State University in Fargo [1]. In this study 3% dehydration of the subjects was produced with cycling and then muscle cramps were induced electrically. Immediately after the cramp was induced the subjects were given either 73.9mL (2.2 ounces) of water or pickle juice. The cramps were 36% shorter in duration (84.6 vs 133.7 seconds) with pickle juice than with water. The pickle juice produced no significant changes in hydration or electrolyte status as measured five minutes after the cramp was induced. While they have no data to back this up, the researchers suggested that the pickle juice inhibits the firing of alpha neurons of the cramping muscle. That gets back to the nervous system theory described above.
I’ll be the first to admit that I don’t have answers for athletes who experience chronic cramping during exercise (I read about one 46-year old athlete who has painful cramps in every workout and no one can figure out why). I hope that some day we will know the cause and have a fix for it (perhaps pickle juice), but until then all I can tell you is to get in the best shape possible for races. Hopefully that does it.
Reference
Miller, K.C., G.W. Mack, K.L. Knight, J.T. Hopkins, D.O. Draper, P.J. Fields and I. Hunter. 2010. Reflex inhibition of electrically induced muscle cramps in hypohydrated humans. Med Sci Sports Exerc 42(5): 953-61.
