Month: September 2011

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Cadence data redux

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- Alex Hutchinson (@sweatscience)

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Last week I posted some data about my running cadence at difference running paces, which sparked plenty of interesting discussion here and at several other sites including Pete Larson’s Runblogger, Amby Burfoot’s Peak Performance and Brian Martin’s Running Technique Tips. All of those folks also sent me some data on their own cadence-vs-pace curves, so I just wanted to share the updated graph:

Without rehashing the whole discussion from last week, the key point I take away from this is that cadence changes as a function of pace (and in a fairly predictable manner, at that). The runners shown here vary dramatically in age, morphology, speed, running shoe preference, running style and probably many other parameters — and as a consequence, at any given pace they have different cadences.

Some might argue that, if all of us took a course to learn the “perfect” form, our cadences would converge toward similar values. That’s an interesting debate — but not the one I’m focused on here. Because even if we did all have the same cadence at 5:00/km, this data suggests very strongly to me that we’d have a faster cadence at 4:30/km, and an even faster cadence at 4:00/km. The moral: any discussion of cadence, whether of an individual or a group, is meaningless without implicitly or explicitly considering pace.

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A few thoughts on the paleo diet

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- Alex Hutchinson (@sweatscience)

***

I was asked in an interview a few days ago for my take on the “paleo diet,” and I figured I may as well share those thoughts here. I’ll start by saying that I’m not an expert in this area — these are just my impressions from the outside! For anyone who’s interested in the scientific rationale behind it, there’s a very comprehensive review paper that was published earlier this year and is freely available online. Anyway, a few scattered thoughts:

It’s not a diet, it’s a lifestyle. I’ve seen this sentiment expressed on a number of paleo-oriented blogs, and I think it’s a very important point. If you want to argue that humans are uniquely adapted to the paleolithic environment because that’s where we spent the most time, it’s meaningless to just consider one part of that environment. If you spend the day sitting on your couch watching TV, then picking up the phone and ordering an authentic ancestral meal from McPaleo’s isn’t going to make you healthy. The review paper focuses on the following key elements of the paleolithic environment:

  • regular sun exposure for vitamin D
  • plenty of sleep, in synch with light/dark cycles
  • lots of physical activity!
  • no exposure to pollution
  • fresh, unprocessed food
  • short bouts of acute stress (tiger!) rather than chronic stress

All of this stuff sounds great — I’m absolutely in favour of every element of this lifestyle.

Plants vs. animals. In the fantasies of some people, going paleo means you get to eat enormous Fred Flintstone-style chunks of meat — for every meal. Not quite: here’s a passage from a paper published in the British Journal of Nutrition last year:

[I]n contrast to common belief, hunting probably played a less dominant role from a nutritional point of view compared with gathering, and on average, it makes up 35% of the subsistence base for present-day worldwide hunter–gatherers, independent of latitude or environment.

This is a point picked up by David Katz in an article earlier this summer: you’re still going to eat, as Michael Pollan would say, “mostly plants.”

The evils of wheat and dairy, and the pace of evolution. Okay, this is where I believe we start to drift away from well-supported science and into the realm of unsupported hypotheses. The basic idea is that, since humans only started farming about 11,000 years ago, our genome hasn’t had time to adapt to these foods. Moreoever, grains like wheat actually contain “antinutrients” that hinder proper digestion and cause chronic inflammation — in everyone, not just those with celiac disease or gluten sensitivity. These results are not widely accepted — or at least, I personally don’t find the evidence convincing.

Moreover, 11,000 years — or 366 human generations — is actually quite a long time. As a result, for example, it’s well understood that the gene allowing for humans to digest milk was selected through evolutionary pressure in populations that domesticated cows. The review paper I mentioned above notes this as a “key exception” to what they otherwise claim is the rule that humans haven’t had time to adapt to agriculture. I, on the other hand, would view it as “key evidence” that humans have had time to adapt to agriculture. Obviously, not all modern humans can digest milk — and those who can’t shouldn’t drink it! But I see no evidence that those who can drink milk should avoid it. Same goes for wheat: it’s certainly true that some people can’t process it adequately, but I’m not convinced that it’s full of antinutrients that are secretly poisoning the rest of us.

Overall, as Stephan Guyenet pointed out in his discussion of the review paper, the evidence seems to support the idea that “the main detrimental change was not the adoption of agriculture, but the more recent industrialization of the food system.” In other words, the diet we should be seeking to emulate is pre-1850, not pre-10,000 BC — which, not coincidentally, once again sounds a lot like Michael Pollan’s advice: don’t eat anything your grandparents wouldn’t recognize as food.

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The Talk Test vs. lactate and ventilatory thresholds

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- Alex Hutchinson (@sweatscience)

***

Figuring out how hard to push is one of the great challenges in exercise. Personally, I’m a big fan of relying on perceptual methods (“how hard does this feel?”) rather than seemingly objective approaches like heart rate or lactate level. Certainly for competitive athletes, learning to interpret your body’s cues is a crucial step to being able to pace yourself properly in a race. But perceived exertion can be pretty tricky for beginners — which is why simple tricks like the “Talk Test” can be very helpful.

In its most basic form, the Talk Test is pretty simple: if you can talk in complete sentences, you’re below threshold. If you can’t talk, you’re above threshold. If you’re in the middle — you can say a few words at a time — you’re pretty close to threshold. So what is this “threshold” we’re talking about? Ah, that’s where it gets complicated. As exercise gets more intense, your body may or may not pass through several thresholds related to breathing rate, lactate accumulation in the blood, and other physiological parameters. The precise definition of these thresholds — and their very existence, in some cases — is hotly debated. As a crude simplification, threshold pace corresponds to the fastest pace you can sustain aerobically, which usually turns out to be the pace you’d hold in a race lasting about an hour.

All of this is by way of introduction to a new study from researchers at the University of New Hampshire, published in the Journal of Sports Sciences, that compared the exercise intensity at various points in the Talk Test to the exercise intensity at the ventilatory and lactate thresholds. Here’s the data, expressed in terms of heart rate and VO2:

“Negative Talk Test” is when the subjects couldn’t talk comfortably; “positive Talk Test” was when they could talk comfortably; “equivocal Talk Test” was in the middle. It’s clear that this middle zone corresponds pretty closely to lactate threshold. This is a bit surprising, since you’d expect ventilatory threshold — when breathing gets significantly harder — to be more closely tied to talking ability. But it’s convenient, because people care a lot more about lactate threshold than ventilatory threshold.

So how do we use this information? Here’s a basic “training zone pyramid” that I included in a Jockology column on pacing last year, based on research by Carl Foster and others about the typical training patterns of endurance athletes:

So most of your training should be below threshold — a common mistake beginners make, since they’re so unfit, is to be pushing above threshold on every bout of exercise. And some of your training should be at threshold — and I’d bet many competitive runners would badly fail the Talk Test during what they claim are “tempo runs” at threshold! On the other hand, casually spinning the wheels of an exercise bike while reading a magazine is unlikely to do much for you, as the press release from the UNH researchers points out:

“If you are beginning an exercise program and can still talk while you’re exercising, you’re doing OK,” Quinn says. “But if you really want to improve, you’ve got to push a little bit harder.”

 

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Why neither “normal” nor minimalist running shoes will disappear

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- Alex Hutchinson (@sweatscience)

***

Which is better: a pill that 75% of the population can take, which produces wonderful benefits for 25% of those who take it; or a pill that 25% of the population can take, which produces wonderful benefits for 75% of those who take it? I was pondering this question while re-reading Peter Vigneron’s long, thoughtful piece about running form, from the June issue of Runner’s World. This passage, in particular, made me think:

Perhaps—and this, too, is speculative—the modern cushioned running shoe makes running easy for the modern runner. This seems like a good thing. Should millions of runners suddenly decide to change their form and then find that running is no longer a manageable activity, it would be a tragedy. The solution to an imperfect state of affairs ought not make things worse—it should not produce more injured, unhappy runners.

One of the common narratives you hear a lot these days is that modern running shoes are the product of an insidious corporate campaign to sell us useless shoes that effectively enslave us by weakening our feet. I find this conspiracy-theory stuff quite tiresome — shoes may or may not be good for us, and of course shoe companies want to sell us anything they can, but I have no doubt that the origin of what Pete Larson calls the “pronation paradigm” was well-intentioned. The simple but often overlooked point is that the shoes caught on. I’d bet that, in 10 years, the recent fad for “toning shoes” will be all but forgotten since they simply don’t work. But running shoes have had remarkable staying power — perhaps because, as Vigneron says, “the modern cushioned running shoe makes running easy for the modern runner.” Or at least some modern runners, some of the time.

Let’s say we accept that, in a perfect world, the barefoot running style is optimal for humans. What if in our postlapsarian modern society, a large proportion of us are simply not equipped to make that transition after decades of sedentary, shod living? Or we can make the transition, but it requires the careful, patient, dedicated, slightly obsessive six-month transition period that barefoot advocates scrupulously recommend? Given the staggeringly high numbers of people who can’t be bothered to do any physical activity, even so much as a brisk walk, despite the overwhelming evidence that it’s the single best thing they could do for all aspects of their physical and mental health, I suspect that the barriers to successful barefoot running will always limit it to a fairly small subset of population.

So that’s what my opening question was about: what if barefoot running is fantastic for a small segment of the population, while running shoes are hit-and-miss but accessible to a much larger portion of the population? What’s the “right” answer to how we proceed? Obviously I chose my sample numbers carefully (so that both versions of the pill help 18.75% of the population, if anyone’s checking the math), but I wonder what those numbers are in reality. How many people can barefoot running reach? How “bad” are normal shoes? In the end, the numbers don’t really matter — because there will always be some part of the population that can succeed with one approach but not the other.

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Full-body compression makes your heart work harder

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

***

Quick look at a study just posted in the European Journal of Applied Physiology, from researchers at the University of Otago in New Zealand. They investigated the effects of full-body compression garments (Skins) on cyclists, looking in particular at three outcomes:

  1. Did it make the cyclists faster?
  2. What effect did it have on their body temperature?
  3. What effect did it have on their cardiovascular workload?

To separate the effects of compression from the effects of wearing a full-body suit in reasonably warm temperatures (24 C), the subjects each did three trials: a control trial in gym shorts; a trial with “properly fitting” Skins; and a trial with oversize Skins. The results:

  1. No difference in cycling performance
  2. Skin temperature was higher by 0.5-0.9 C during exercise when wearing compression gear, but core temperature was unaffected.
  3. Their hearts had to work about 5% harder with the compression gear on, and they finished with a heart rate 4-7% higher than in the control condition.

The authors make their skepticism clear pretty much from the start: the first sentence of the abstract is “Sporting compression garments are used widely during exercise despite little evidence of benefits.” They make several interesting points in the paper — for instance, the vast majority of “evidence” cited for increased venous flow and reduced venous pooling comes from studies of people (generally with some sort of circulatory condition) at rest. Do the same findings apply during exercise? It may be that the “calf muscle pump” — the squeezing of the calf that shoots blood back toward the heart, which supposedly gets a boost from compression socks — is already acting at maximal capacity during vigorous exercise.

Bottom line from this study: the garments didn’t really make much difference (the mild changes in temperature and cardiovascular function, though negative, weren’t enough to be a big issue). The authors are careful to note that the study has nothing to do with whether compression garments help recovery. But as far as wearing them during exercise, this certainly doesn’t change my opinion that wearing a full-body speed-suit while jogging on a hot summer day (and I see plenty of people doing that here in Sydney!) may look cool, but doesn’t do anything for your performance.