Posts Tagged ‘cramps’

Muscle cramps risk factors: tapering, stretching and pacing

March 22nd, 2011

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!

Cramping in Ironman triathlons: not dehydration or electrolytes

February 3rd, 2011

Another interesting study in the British Journal of Sports Medicine, posted online in December while I was away. It’s a prospective study that 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. 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 cramping group lost 2.8% body mass compared to 3.1% in the non-crampers; crampers’ sodium levels dropped 0.1% (+/- 1.9%), while the non-crampers increased 0.4% (+/- 2.6%).

The study comes from Martin Schwellnus’s group at the University of Cape Town. I wrote about Schwellnus’s theory of “altered neuromuscular control” for cramps last July, after returning from a visit to his lab. At the time, he was analyzing some data that he said suggested that crampers tend to be those who set faster time goals and start faster relative to their fitness, and who have trained more in the final week before the race (thus leaving their muscles fatigued). That suggested that realistic goal setting and an appropriate taper would minimize your risk.

The new study only bears part of that out. The three factors that predicted cramping were (1) faster predicted race time, (2) faster actual race time, and (3) previous history of cramping. Training volumes and paces for the final week before the race were more or less identical in the two groups, which means that in this group of athletes, a bad taper wasn’t to blame.

The fact that faster predicted and actual finishing time was associated with cramping is sort of bad news, because it doesn’t offer any simple solutions. The two groups were matched in terms of training history and personal best performances, so on the surface you’d expect them to aim for similar times. But it turns that those who aimed higher were more susceptible to cramps — and achieved better performances. So it seems (albeit from a single, isolated study) that cramping is just one of the many unavoidable risks associated with getting as close as possible to your limits, especially if you happen to have a (genetically determined?) history of cramping. You’d probably find a similar pattern if you measured the likelihood of dropping out or having a very big positive split: those who aim highest are most likely to blow up or drop out, but are also most likely to produce faster performances.

UPDATE Feb. 3: There’s quite a lively debate on this topic going on over at Slowtwitch. I just posted to address a couple of questions; my response is below: Read more…

Cramps: training, pacing, genetic factors and pickle juice

July 8th, 2010

I’m back from a really incredible hiking trip in Papua New Guinea, during which I sweated out buckets of fluid but didn’t develop any muscles cramps… which brings me to the Jockology column in today’s Globe and Mail.

Back in April, I blogged about an interesting study reporting that pickle juice made muscle cramps disappear more quickly than water — an inexplicable finding if you subscribe to the theory that dehydration and/or electrolyte losses cause muscle cramps. Since then, another interesting study from the same group has appeared, and I also had the opportunity to visit the lab of Martin Schwellnus at the University of Cape Town, who proposed a different explanation for cramps a little over a decade ago. Today’s column takes a look at the evidence for Schwellnus’s “altered neuromuscular control” theory of muscle cramps.

If you’re already familiar with the theory, the most interesting new bit of data in the article comes from a new study that Schwellnus hasn’t published yet:

Interestingly, Dr. Schwellnus’s study of triathletes found that those who developed cramps had set higher pre-race goals and started at faster paces relative to their previous best times compared with non-crampers. And in a further study that has not yet been published, he found that crampers tend to have trained more in the final week before the race and have elevated blood levels of enzymes related to muscle damage before they start. [read the whole article...]

In other words, you may have set the stage for your muscle cramp by not resting enough before a race, and by starting too fast relative to your training. It’s likely a result of several different factors coming together, including genetic predisposition — but for those who are cramp-prone, the overtraining link offers something concrete that you can try changing before your next competition.

Pickle juice stops muscle cramps

April 21st, 2010

No, really, this is a serious blog entry. There’s an article in the May issue of Medicine & Science in Sports & Exercise by researchers at Brigham Young University called “Reflex Inhibition of Electrically Induced Muscle Cramps in Hypohydrated Humans,” and that’s what it says:

The most significant and novel observation of this study was that ingesting small volumes (73.9 +/- 2.7 mL) of pickle juice alleviated electrically induced muscle cramps in mildly hypohydrated (3%) humans. Pickle juice required approximately 85 s to alleviate muscle cramps (cramp duration after ingestion ranged from 12 to 219 s). Although this was much longer than the purported claims of pickle juice’s efficacy, it still relieved a cramp 45% (85 vs 153 s) faster than when no fluid was consumed. In contrast, ingesting similar volumes of deionized water had no therapeutic effect on cramp duration (cramp duration after ingestion ranged from 71 to 246 s).

What’s interesting about this is not so much the promise of a “cure” for muscle cramps. (There are some reasons to think that downing a bunch of vinegar and salt probably isn’t a great habit, for one thing.) Instead, it’s how it stops cramps that is intriguing and suggests that conventional thinking on cramps may be mistaken.

The pickle juice cure has been around for at least a decade (it was described in a 2000 article in the Journal of Athletic Training), and most people assumed that it had something to do with all the electrolytes. But the authors of this new study aren’t convinced. First of all, the amount of electrolyte in 73 mL of pickle juice has a negligible effect on concentrations in the body. Second, the 85 seconds it took (on average) to relieve the cramps is far too short for the pickle juice to exit the stomach, be absorbed by the small intestines, and reach the relevant part of the body. Earlier studies have found that it takes at least 30 minutes for small volumes of pickle juice to leave the stomach.

Instead, the researchers suggest that the pickle juice acts on neural reflexes — a plausible suggestion, given that earlier experiments have found that vinegar can provoke reflexes and affect neurotransmitter levels. This fits with an alternate theory that cramps have nothing to do with dehydration or electrolyte loss, first proposed in the 1990s by Martin Schwellnus of the University of Cape Town:

Schwellnus et al. proposed that [cramps] were due to neuromuscular fatigue. Neuromuscular fatigue is thought to create an imbalance between muscle spindle and Golgi tendon organ activity, resulting in increased alpha motor neuron excitability. Thus, if [cramps] are caused by an imbalance between excitatory and inhibitory stimuli at the alpha motor neuron pool, pickle juice ingestion may cause an increase in inhibition from supraspinal sources, thereby resulting in cramp alleviation.

If you’re interested in the details of Schwellnus’s theory and the controversies surrounding muscle cramps, the Science of Sport blog did a good series on it back in 2007 (Part 1, Part 2, Part 3 and Part 4). It’s interesting stuff — and now, courtesy of pickle juice, there’s some new evidence.