Studies have tested athletes with dehydration – both at a 3% and 5% loss of their body weight – and found that these athletes did not have increased susceptibility to cramps (1,2). Along the same lines, ultra distance runners who experienced cramps were not more likely to be dehydrated compared to those who did not have cramps (3). Similar results were found among Ironman triathletes (4,5).
Studies as early as 1986 study suggested that cramps may not be due to hydration and electrolyte status. Marathon runners with muscle cramps did not have different electrolyte levels compared to those without cramps (6). The Ironman study that looked at dehydration also looked at electrolyte values, and did not find any differences between cramping vs. non-cramping athletes (5).
There’s also research looking at certain individual electrolytes...
One small study looked directly at a favorite food of athletes – bananas – and investigated the effect of eating 0, 1, or 2 of them after exercise in the heat. They concluded that the changes in potassium and glucose that happened when the bananas were eaten were not large enough to have an impact on muscle cramps (7).
Magnesium has been another postulated nutrient that could impact cramp risk, however a 2012 Cochrane Review did not find any randomized control trials which investigated magnesium on exercise-associated muscle cramps (8).
Interestingly, some research has reported that cramping athletes have lower serum sodium levels compared to those without cramps – but these have still fallen in the normal range (4). Perhaps for these athletes, a “lower normal” might be enough to contribute to cramping, but it's likely not the definitive or only answer.
So what really causes muscle cramps?
Most likely, tired and fatigued muscles. Here is what has been scientifically linked to muscle cramps in the recent research:
1. Increased speed and intensity, since it may lead to quicker neuromuscular fatigue (9, 10, 11)
2. Possible genetic component or family history (9)
3. History of tendon or ligament injuries (depending on how recovery was approached, this may have caused increased stress or fatigue in surrounding muscles) (9)
Does this mean you shouldn’t pay attention to hydration and electrolytes at all? Of course not. Proper hydration and electrolyte balance during exercise have other important benefits outside of cramping. For example, losing more than 2-3% of your body weight from dehydration may lead to decreased performance. Not taking in enough sodium over a long event may affect your risk of hyponatremia (also known as “water overload” - though fluid balance is certainly the larger factor there). Not to mention, outside of exercise, getting enough potassium daily may help control blood pressure.
In addition, you could certainly argue that there are many anecdotal reports of athletes reporting an improvement in muscle cramps with proper hydration and electrolyte balance. From a personal standpoint, I know I had a better experience with muscle cramps when I switched to a higher sodium sports drink. Whether that’s a true effect or placebo is up for debate. And some research shows that a carb and electrolyte containing sports drink may not prevent cramps, but may prolong the amount of time until those cramps occur (12).
The bottom line? Cramping muscles are most likely due to neuromuscular fatigue – so be sure to train well in order to prepare yourself for your race and avoid going out at pace that's too quick for you. But if drinking enough sports drink or eating a post-race banana helps you too, then go for it!
Share with us: What do you do to prevent muscle cramps?