Sidney Crosby, chiropractic neurology, and the limits of evidence

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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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The good news: Sidney Crosby is back from the concussions that kept him on the bench for more than 10 months, and he had two goals and two assists in his return against the Islanders last night. But one downside, a reader pointed out to me in an e-mail, is that Crosby’s return may give added credibility to “chiropractic neurology,” the alternative therapeutic approach that Crosby turned to during his rehab. What exactly is this? I don’t know — and I’m not alone:

It’s a field that’s unfamiliar to many traditional doctors, including Randall Benson, a neurologist at Wayne State in Detroit who has studied several ex-NFL players. Says Benson, “It’s very difficult to evaluate what kind of training, expertise or knowledge a chiropractic neurologist has since I have never heard of [the discipline].”

That’s a quote from David Epstein and Michael Farber’s excellent look at Crosby’s rehab from Sports Illustrated in October. A couple of other interesting quotes:

In 1998, at Parker University, a Dallas chiropractic college, Carrick [the chiropractic neurologist who Crosby worked with] worked on Lucinda Harman before 300 students. Two car accidents and a neurotoxic bite from a brown widow spider had left Harman, herself a Ph.D. in experimental psychology, wheelchair-bound and with headaches, during which she saw spots.”[Carrick] asked if they were red and yellow,” she says. “I said, ‘No, they’re green, blue and purple.’ ” Carrick informed the audience that this meant her brain was being drastically deprived of oxygen and that, without treatment, she had six months to live. Harman, now 59, says simply, “Miracle.” But Randall Benson says that “there’s nothing out in peer-reviewed literature supporting” an association between the color of spots a patient sees during a headache and the severity of the oxygen deprivation in the brain.

[…]

Carrick, who has had a handful of studies that have appeared in scientific journals, has never published data on vestibular concussions. “We don’t have enough time to publish studies,” he says, “but we’re doing a large one at Life [University] right now.”

It’s a great piece — fair but rigorous. In some ways, though, the most important quote may be the kicker:

“I don’t think this is a case of trying to do something wacky,” Crosby says. “When someone came along and invented the airplane, people must have thought they were out of their mind. Who thinks he can fly? I’m sure people thought that person might have been stretching it a bit… . At the end of the day, as long as the person getting the care is comfortable, I think that’s what’s important.

Much as my evidence-based personality protests, I do think there’s some truth to that. Especially in cases like this, where — as with so many health conditions — there isn’t a well-established “standard-of-care” treatment. It’s totally different from, say, Steve Jobs choosing “alternative” forms of cancer treatment instead of surgery. In that case, the potential benefits of the surgery are well-known and well-understood. But many people face health conditions where the verdict of the Cochrane review is basically “there is insufficient evidence to conclude that ANY interventions do any good.” In that case, it’s hard to argue against trying other, unproven approaches rather than simply doing nothing.

Of course, sports medicine is a little different — it’s not life-or-death. For pro athletes, the incentive to try anything and everything in order to return to play (and earn money during their brief career window) is enormous. If I were Tiger Woods or Terrell Owens, I would have tried platelet-rich plasma to speed tendon healing too, despite the lack of evidence that it actually works. The problem is that the use of these therapies by sports stars gives the general public the impression that they’re proven, established treatments — hence the huge surge in PRP over the last few years. Will the same thing happen with chiropractic neurology? I hope not. But on the other hand, if someone who’s been in two car accidents and been bitten by a neurotoxic spider is in pain and hasn’t been able to get relief from conventional treatment, I’d have a hard time criticizing them if they decided to give it a try.

Cadence in elite runners increases as they accelerate

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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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One quick graph from a new study by Robert Chapman and his collaborators at the University of Indiana, just published online in Medicine & Science in Sports & Exercise:

This is data from 18 elite runners (12 male, 6 female), showing their stride frequency as a function of speed. For reference, 3.00 Hz corresponds to 180 steps per minute; 3.3 Hz corresponds to about 200. On the speed axis, 4.0 m/s is 4:10 per km, and 7.0 m/s is 2:23 per km. In other words, these are FAST paces. The key point: they get faster, in part, by quickening their cadence. There’s no magic cadence that they stay at while lengthening their stride to accelerate.

Interesting wrinkle: the women have faster cadence than the men at any given speed. Chapman assumes this is partly due to the fact that the men are taller — but even normalizing by height doesn’t quite erase the difference. (And that even ignores the argument that, as I blogged about here, cadence should be proportional to the square root of leg length, not leg length itself.) The remaining difference, Chapman hypothesizes, could be due to “application of greater ground forces by the men or differences in muscle fiber type distribution.” This makes sense: if you’re stronger (as the men, on average, will be), you’ll have stronger push-off, longer stride, and thus shorter cadence at any given speed. But it seems pretty clear that height plays at least some role.

Paleo, the pace of evolution, and chronic stress

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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My Jockology column in today’s Globe and Mail takes a look at the paleo diet — or rather, the paleo “lifestyle.” The column is actually in the form of an infographic in the paper, beautifully illustrated as “cave art” by Trish McAlaster. Unfortunately, the online version so far just lifts the text, without any of the data and graphics that accompany it. Nonetheless, it’s hopefully worth a read!

As a teaser, here’s an excerpt from a section on how the pace of evolution has changed over the past few thousand years, and what that means for the quest for the perfect “ancestral” diet:

The paleo diet depends on the assumption that our genes haven’t had time to adapt to the “modern” diet. Since evolution depends on random mutations, larger populations evolve more quickly because there’s a greater chance that a particularly favourable mutation will occur. As a result, our genome is now changing roughly 100 times faster than it was during the Paleolithic era, meaning that we have had time to at least partly adapt to an agricultural diet.

The classic example: the ability to digest milk, which developed only in populations that domesticated dairy animals. More than 90 per cent of Swedes, for example, carry this mutation. Finnish reindeer herders, in contrast, acquired genes that allow them to digest meat more efficiently, while other populations can better digest alcohol or grains. The “ideal” ancestral diet is most likely different for everyone. [READ THE WHOLE ARTICLE]

And, as another teaser, here’s a section of Trish’s infographic illustrating the difference between the acute stress of the paleo lifestyle compared to the chronic stress of modern life:

Compression gear during interval workouts: a new possibility

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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An interesting wrinkle in the debate over whether compression garments do anything during exercise to improve performance, from a new Australian study just posted in the Journal of Strength & Conditioning Research. The situation so far:

  • Every time you take a step while running, the flexing of your calf muscle operates something called the “calf muscle pump” — basically, your calf literally squeezes the blood vessels in your lower leg, helping to shoot oxygen-depleted blood back toward the heart.
  • Graduated compression of the lower leg (i.e. tighter at the ankle, looser at the knee) is thought to enhance the action of this calf muscle pump, by helping it to squeeze harder. This should reduce the load on your heart and speed the circulation of blood through your body, possibly enhancing performance.
  • One argument against the idea that compression garments boost performance is that, when you’re running hard, the action of the calf muscle pump is already maxed out, so adding more compression doesn’t help. You can’t squeeze more blood from a stone!

The new study put 25 rubgy players through a form of interval workout: basically 5:00 easy, 5:00 medium, 5:00 hard, 5:00 easy, 5:00 hard, 5:00 easy. They each did the test twice, once in running shorts and once in full-leg graduated compression bottoms. The researchers measured a bunch of variables (heart rate, oxygen consumption, lactate levels, blood pH) during each stage of the workout. There were basically only two elements where the data was significantly different between shorts and tights: in the fourth and sixth intervals (i.e. the easy recovery intervals), heart rate and lactate levels were both significantly lower in compression tights.

On the surface, this fits nicely with the ideas above. The tights don’t help when you’re running fast, since the calf muscle pump is maxed out; but during the easy recovery, the compression does help, resulting in lower lactate and heart rate — and, in theory, better performance on the subsequent hard section.

This is the problem, though: the study didn’t actually measure performance. The pace during each interval was predetermined, so we don’t know whether this difference in physiological parameters actually translates into better real-world performance. That’s a point that was highlighted in another Australian compression study that I blogged about back in August. That study also found physiological “improvements” from compression — but in that case, they also measured performance and found no difference. As the researchers wrote:

However, the magnitude of this improved venous flow through peripheral muscles appears trivial for athletes and coaches, as it did not improve [time-to-exhaustion] performance. This would suggest that any improvement in the clearance of waste products is insufficient to negate the development of fatigue.

Bottom line: I remain skeptical that wearing compression during a run will allow you to run faster. (Note that this is entirely separate from the question of whether wearing compression during and after a run will allow you to avoid or recover more quickly from muscle soreness, a claim that has somewhat better support.) This new study raises the intriguing possibility that compression might boost active recovery during interval workouts — but until it’s directly tested in a performance context, it’s just a hypothesis.

The case against antioxidant vitamin supplements

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)

***

The December issue of Sports Medicine has an enormous, detailed review of research on the effect of antioxidant (i.e. vitamin C, vitamin E, coenzymeQ10, etc.) supplements on training. To most people, this seems like a no-brainer: what could be smarter than popping a multivitamin as “insurance” in case your diet isn’t giving you all the vitamins you need? But (as I’ve blogged about before) there’s an emerging school of thought arguing that taking antioxidants can actually block some of the gains you’d otherwise get from training. Here’s how I explained the debate back in April:

The traditional theory goes like this: strenuous exercise produces “reactive oxygen species” (ROS), which cause damage to cells and DNA in the body. Taking antioxidant supplements like vitamins C and E helps to neutralize the ROS, allowing the body to recover more quickly from workouts.

The new theory, in contrast, goes like this: strenuous exercise produces ROS, which signal to the body that it needs to adapt to this new training stress by becoming stronger and more efficient. Taking antioxidant supplements neutralizes the ROS, which means the body doesn’t receive the same signals telling it to adapt, so you make smaller gains in strength and endurance from your training.

The new paper comes down firmly on the side of the latter view:

The aim of this review is to present and discuss 23 studies that have shown that antioxidant supplementation interferes with exercise training-induced adaptations. The main findings of these studies are that, in certain situations, loading the cell with high doses of antioxidants leads to a blunting of the positive effects of exercise training and interferes with important [reactive oxygen species]-mediated physiological processes, such as vasodilation and insulin signalling.

So is this definitive? Far from it. As the review notes, there have been a few studies that found beneficial effects of antioxidant supplements on exercise performance, tons that have found no effect, and a few (23, to be exact) that have found negative effects. What most of the studies have in common:

As commonly found in sports nutrition research, the vast majority do not adhere to all the accepted features of a high-quality trial (e.g. placebo-controlled, double-blind, randomized design with an intent-to-treat analysis). Indeed, most studies fail to provide sufficient detail regarding inclusion and exclusion criteria, justification of sample size, adverse events, data gathering and reporting, randomization, allocation and concealment methods, and an assessment of blinding success. The poor quality of the majority of studies in this field increases the possibility for bias and needs to be always considered when evaluating the findings.

This is a really important point to bear in mind, and not just when it comes to sports nutrition. Whatever the supplement, training method, or piece of equipment you’re talking about, there’s nearly always a crappy, poorly executed study that seems to “prove” that it works. So where does that leave us? On this topic, I’m in agreement with the authors:

We recommend that an adequate intake of vitamins and minerals through a varied and balanced diet remains the best approach to maintain the optimal antioxidant status in exercising individuals.