Training in the heat this summer has taken a toll on many runners. I hear many of you complaining that your pace has slowed down or you are just not training as much. Some, however, have suffered the much feared…muscle cramps – in a run, bike or pool. Is it the heat, or some other evil beast? I was a victim just this week when I had done a long run in the morning and then was out very far away from home on a 50 mile bike when I started cramping. First my calves, then my quads. Not fun!
Two studies have emerged recently that have shed some light on muscle cramp prevention as well as treatment.
If we look at the history and theory of muscle cramping, it’s traditionally thought that electrolyte imbalances were solely to blame. However, this theory of why cramping occurs is being thrown into question. It appears multifactorial. For example, if it’s a systemic depletion of electrolytes, why is it the muscles that are working harder are the ones that usually cramp? Why isn’t it the entire body?
Secondly, several studies comparing cramp-prone athletes with non-cramp-prone peers have found that that hydration and electrolyte levels in the two groups are almost indistinguishable before and after the race. One such study is found here. This study concluded “EAMC (Exercise Associated Muscle Cramps) in Ironman triathletes is not associated with a greater percent body mass loss or clinically significant differences in serum electrolyte concentrations.”
That brings us to the first study, not yet published but reported on here, which deals with overtraining and cramping. This study of triathletes found that those who developed cramps had started at faster paces relative to their previous best times compared with non-crampers. And in a further study (again, not yet published), the same researchers found that crampers tend to have trained more in the final week before the race. As a result, the had elevated blood levels of enzymes related to muscle damage before they start.
This means that if you haven’t rested enough before a race or if you start a race or a training session too hard, you are setting yourself up for muscle cramps. It’s likely a result of several different factors coming together, including genetic predisposition, but at least we can now try to change some factors to prevent the cramps in the first place.
The next study (published here) is also to do with cramping, but instead of prevention, it’s to do with treatment. Here, they dehydrated subjects, then electrically induced muscle cramps. One group received nothing to treat it, the second group received deionized water and the last group….around 70ml of pickle juice (about 2.5 oz).
The results were thought provoking: the pickle juice group’s cramps stopped about 45% faster than the no treatment group and 37% faster than the deionized water group. On average – the pickle juice took around 85 seconds to stop the cramps. Why is it thought provoking? Because we know pickle juice electrolytes would take around 30 minutes to go through the stomach, absorbed through the intestines and get to the muscles. So, if it takes 30 mins for the electrolytes in the pickle juice to actually get to the muscles, yet it stopped the cramping in 85 seconds, it’s obviously not the actual electrolytes. Everyone assumed that the electrolytes were the cause of muscle cramps…maybe not!
The researchers suspect that that mechanism is simply – exhaustion. Biochemical fatigue, or direct fatigue of the muscle. When a muscle is very tired, we know that certain mechanisms within muscles cause them to start misfiring. Small nerves that should keep the muscle from overcontracting malfunction, and the muscle bunches when it should relax. So, they think that the pickle juice somehow acts on neural reflexes – receptors in the mouth and throat disrupt the misfiring neurons. This fits with an alternate theory that cramps have nothing to do with dehydration or electrolyte loss, first proposed in the 1990s byMartin Schwellnus of the University of Cape Town:
Early observations have led to the belief that cramps in athletes are caused by shortages of electrolytes (sodium, chloride, and magnesium), dehydration, or heat. Despite a lack of scientific support for these theories the term “heat cramps,” which was first used in 1935, is still in use today. However, there is increasing evidence that EAMC is caused by muscle fatigue which results in a disturbance in the normal control of the nerves that cause muscle contraction. A number of researchers who have reviewed the medical literature now conclude that this “altered neuromuscular control” mechanism is probably responsible for the majority of EAMC in athletes 21-23. As with other forms of cramping, a small proportion of EAMC may also be as a result of underlying medical disease or drugs 21;23.
Does this all say to stop with the electrolyte replacement fluids when running? No, of course not. There are still things like hyponatremia that we have to worry about. All this is saying is that exercise induced muscle cramping, while thought to be due to electrolyte deficiency, really has more to do with fatigue. If you’re prone to muscle cramps, watch for overtraining, start your races conservatively and, if you must, bring some pickle juice with you!