Muscle cramps risk factors: tapering, stretching and pacing

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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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!

Athletes have superior street-crossing abilities

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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How’s this for a compelling reason to take up sports, from the conclusions of a newly published University of Illinois study:

Compared to non-athletes, collegiate Division I athletes showed higher street crossing success rates, as reflected by fewer collisions with moving vehicles.

It’s actually an interesting study, though it’s hard not to snicker while reading it. Researchers assembled 18 D1 athletes from a variety of sports (baseball, XC, gymnastics, soccer, swimming, tennis, track, wrestling) and 18 non-athlete controls matched for age, gender, height, weight, GPA and video-game experience, then had them all try to successfully cross a busy street in a 3-D virtual environment, while walking on a manual self-paced treadmill. The results: athletes made it to the other side without getting splatted 72.05% of the time, while non-athletes only made it 55.04% of the time.

The purpose of the study was to find out whether sports training improves multitasking ability:

An ability to efficiently process information is said to improve multitasking performance. That is, if information passes through the bottleneck efficiently and quickly, more information can be processed in a shorter time frame and performance can be maximized.

The athletes also outperformed the non-athletes in a simple test of reaction time — that difference alone is enough to account for the difference in street-crossing success. Of course, there’s a glaring cause-and-effect question here, which the researchers acknowledge:

We speculate that athletes are faster multitaskers than non-athletes, but it is also possible that successful virtual reality street crossers with fast processing speed are more likely to excel at sports.

It’s by no means obvious to me which direction the arrow of causality runs here. I suspect it’s a bit of both. Interestingly, these researchers are also part of the group that has been publishing some very encouraging findings about the effects of aerobic exercise on the brain. Just last month, they published a Proceedings of the National Academy of Sciences paper showing that aerobic exercise increases the size of the hippocampus by 2% in older people, reversing the effects of 1-2 years of age-related decline. In this case, cause and effect were clear.

Bottom line: sports skills may help you cross the street successfully, but if you want to remember how to get home again, make sure you’re doing some aerobic exercise.

How evolution keeps you on the couch

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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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Mark Fenske, a neuroscientist at the University of Guelph, has an interesting article in the Globe and Mail about how evolutionary forces on our brains affect our motivation to exercise. His basic argument is that we’re wired to avoid wasting energy, since our ancestors needed to make sure they’d have enough energy to find food or flee from danger. And recent neuroimaging studies (he’s not specific about which studies, by whom, and under what conditions) offer some support for this idea:

When subjects were considering whether to perform a given action, neural activity within one part of the striatum, the putamen, was found to decrease with the amount of physical effort the action would require… By helping to produce an aversion to unnecessary physical activity, the striatum may be partly to blame for the growing number of couch potatoes in Western societies.

Seems fairly intuitive — it would be surprising if we hadn’t evolved some such mechanism. But does this mean we’re incapable of overcoming this barrier to exercise? Of course not:

A number of studies indicate that increasing the reward associated with an effortful action can lead to its being chosen over an easier option. And brain scans show that the size of such a reward is associated with activity in the nucleus accumbens, which is another part of the striatum linked to motivation.

Again, this is quite painfully obvious on an intuitive level, though it’s interesting that scientists are zeroing in on which specific parts of the brain are responsible for these drives. The real pay-off, and the reason I’m linking to the article, comes in Fenske’s conclusion. We can trick the brain and tip the balance in favour of exercise, he says, by reminding ourselves of the well-established mental and physical benefits of exercise:

[B]y learning and thinking about exercise-related rewards we can strategically increase the incentive value of physical activity. This may explain why being reminded of such benefits, and how I always feel better after running than before, is so effective at getting me out the door.

To some extent, that’s what this blog is all about! The more we learn about all the different ways exercise benefits us, the easier it is to get out the door.

(And there’s a postscript too: exercise leads to physical changes in parts of the basal ganglia related to cognitive control. So the more you exercise, the better you get at overcoming your ancient brain’s aversion to “needless” effort.)

Exercise and poop

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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You may want to skip this post if you’re about to eat…

Swedish scientists just published a delightful and highly detailed study comparing the gastrointestinal characteristics of a group of 15 elite orienteering during a week of heavy training, and again during a week of rest. (I don’t generally keep up to speed on the Scandinavian Journal of Gastroenterology, so thanks to Amby Burfoot for the tip-off!) Most people won’t be surprised to learn that, during the heavy training week, subjects had more bowel movements (1.5 per day versus 1.3) and looser stools (4.2 versus 3.9 on the Bristol Stool Form Scale, which rates stools from a hard, nut-like 1 to a watery 7).

The study also delved into much greater detail, using “radiopaque markers” whose progress could be followed through the digestive system using fluoroscopic imaging (essentially a real-time X-ray). Throughout the week, the subjects ate 10 little ring-shaped markers with breakfast each day; then on the final day, they ate 20 little spherical markers with breakfast, and were imaged every half-hour for the next eight hours. The spheres were used to track progress out of the stomach and through the small intestine (where most nutrient absorption occurs), which is measured in hours. The number of ring-shaped markers still in the body allowed the researchers to calculate how long food was taking to travel through the colon, which is measured in days.

The key results: gastric emptying (how quickly food left the stomach) was not significantly different during the two weeks (average of 1.8 hours during the resting week, 2.4 hours during the exercise week). Transit through the small intestine was significantly quicker during the training week (3.7 hours versus 6.9 hours on average). Transit through the colon wasn’t significantly different (1.2 days during training, 1.4 during rest).

So what does it all mean? Well to me, this is one of those “Am I normal?” studies: without going into excessive detail, it’s nice to see that my personal observations match up with typical patterns. One of the questions that remains unanswered is: are athletes in training less efficient at absorbing nutrients from their food since they’re forcing the food through their small intestine more quickly?

Artificial intelligence, the Singularity, and Robert J. Sawyer

THANK YOU FOR VISITING SWEATSCIENCE.COM!

As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.

- Alex Hutchinson (@sweatscience)

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Totally off-topic here, but I just wanted to highlight an essay of mine that appears in next month’s Walrus magazine (and is now available online). Using Robert J. Sawyer‘s WWW trilogy (whose final volume is about to be released) as a jumping off point, it explores some of the issues surrounding computers whose intelligence is beginning to approach human-like levels:

If you’ve got any spare change, the Lifeboat Foundation of Minden, Nevada, has a worthy cause for your consideration. Sometime this century, probably sooner than you think, scientists will likely succeed in creating an artificial intelligence, or AI, greater than our own. What happens after that is anyone’s guess — we’re simply not smart enough to understand, let alone predict, what a superhuman intelligence will choose to do. But there’s a reasonable chance that the AI will eradicate humanity, either out of malevolence or through a clumsily misguided attempt to be helpful. The Lifeboat Foundation’s AIShield Fund seeks to head off this calamity by developing “Friendly AI,” and thus, as its website points out, “will benefit an almost uncountable number of intelligent entities.” As of February 9, the fund has raised a grand total of $2,010; donations are fully tax deductible in the United States… [READ THE REST OF THE ESSAY]

And for the record, I wrote this before Watson beat the puny humans on Jeopardy!