Muscle cramps risk factors: tapering, stretching and pacing


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I’ve written a few times now about the “new” theory of muscle cramping advanced by Martin Schwellnus of the University of Cape Town and his colleagues, most recently last month. In a nutshell, he argues that muscle cramps have nothing to do with dehydration or electrolyte depletion, but result from “altered neuromuscular control” (for an more detailed explanation, see this article).

Schwellnus and his colleagues have just published a new study online at the British Journal of Sports Medicine — a prospective study of 49 runners at the 2009 56K Two Oceans marathon. And it produced some very interesting results. Twenty of the runners reported cramps during or within six hours after the race, compared to 29 non-crampers. The two groups were statistically identical in many important respects: age, weight, height, BMI, sex, training history, recent and all-time personal best times, finishing times during the race. But they differed in a few key areas:

  • Pacing: Even though the two groups had similar best times and similar pre-race goals, the group that ended up cramping split the halfway mark 13 minutes faster than the non-crampers on average (144 minutes versus 157 minutes).
  • Tapering: In the three days prior to the race, the crampers trained 1.1 hours on average, while the non-crampers trained 0.6 hours on average. This despite the fact that the non-crampers actually did marginally more training overall in the final week (31.8 km versus 26.5 km).
  • Muscle damage: Perhaps related to the inadequate taper, the eventual crampers had higher levels of creatine kinase before the race, indicating the presence of muscle damage. They were also more likely to report soreness in their hamstrings.
  • Stretching: 92.9% of the crampers reported stretching before exercise, while just 54.6% of the non-crampers reported stretching. Of course, this could simply be because those prone to cramp are more likely to stretch.

Does this settle the cramping debate? Nope, but it should provide a little more fuel for the fire!

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