25 Feb 2013
Experts used to believe that cramps were caused by dehydration or electrolyte depletion. But no studies have actually linked the idea that dehydration or electrolyte depletion is the reason one athlete cramps and another doesn’t. Strong experimental evidence for either theory is lacking.
A 2011 study from University of Cape Town researchers looked at 209 Ironman triathletes before and after a race, and tried to detect any differences between the 43 who developed muscle cramps and the 166 who didn’t (1). The major finding is that there was no significant difference in the levels of dehydration or electrolyte loss between the two groups, challenging the prevailing electrolyte-depletion hypothesis of cramps.
The same research team studied Ironman South Africa athletes to analyze serum electrolyte levels, and even though the decrease in sodium concentrations was significant, the difference compared to a control group was within the normal clinical range of post-race serum sodium concentrations (2). They were unable to correlate decreased sodium concentration to an increase in exercise-associated muscle cramping. Instead, they concluded “Acute EAMC in ironman triathletes is not associated with a greater percent body mass loss or clinically significant differences in serum electrolyte concentrations. The increased EMG activity of cramping muscles may reflect increased neuromuscular activity.”
Schwellnus and his colleagues published a study later the same year in the British Journal of Sports Medicine looking at 49 runners in the 56K Two Oceans Marathon in Cape Town (3). Those who suffered cramp were more likely to have set off too fast relative to their fitness and have trained more in the final week before competition, thus leaving their muscles fatigued.
Researchers are now studying an alternative theory that pins much of the blame for muscle cramps on factors like training, recovery and pacing, as well as genetic susceptibility- the theory of “altered neuromuscular control”. In other words, muscle fatigue leading to abnormal functioning at the spinal level of the muscle contraction mechanism.
Here are some ways that may help to prevent cramps:
* Train for the conditions (pace, terrain, temperatures, duration, etc.) you plan to compete in
* Follow a regular stretching program
* Work on correcting any muscle imbalances or incorrect movement patterns; develop an efficient technique required for your sport
* Take in enough carbohydrates before, during and after events > 2hours; the amount will vary among individuals but aim for 250 – 400 calories per hour during the event
* Hydrate properly during the event, especially events lasting longer than 3 hours
If you do cramp, try to:
* Slow down and lower the intensity of the activity
* Stretch and try to relax the affected muscle(s)
* Apply pressure to the affected muscle group(s) to get the muscles to “release”
- Schwellnus MP, Drew N, Collins M (2011) 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 Jun;45(8):650-6. doi: 10.1136/bjsm.2010.078535. Epub 2010 Dec 9.
- Sulzer NU, Schwellnus MP, Noakes TD. Serum electrolytes in Ironman triathletes with exercise-associated muscle cramping. Med Sci Sports Exerc. 2005 Jul, 37(7):1081-5.
- Schwellnus MP, Allie S, Derman W, Collins M (2011) Increased running speed and pre-race muscle damage as risk factors for exercise-associated muscle cramps in a 56 km ultra-marathon: a prospective cohort study. Br J Sports Med. Nov;45(14):1132-6. doi: 10.1136/bjsm.2010.082677. Epub 2011 Mar 13.