Author: alex

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The beet goes on: nitrates improve cycling time trial performance

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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)

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Wow. This study is really impressive. Drinking 500 mL of beet juice 2.5 hours before a cycling time trial improves 4 km TT time by 2.8% and 10 mile TT time by 2.7%. On the one hand, this shouldn’t be surprising, because there have been a bunch of recent studies showing beet juice boosting time-to-exhaustion and reducing oxygen cost… But still, those types of studies often don’t end up translating into real differences in the parameter that matters: actual performance. So, as I said: Wow.

The study, published online last week in Medicine & Science in Sports & Exercise, is legit. It’s from Andrew Jones’s group in Exeter. It’s a properly designed placebo-controlled crossover study. The placebo was beet juice with the nitrates (the active ingredient) filtered out with an ion resin, thus indistinguishable from the active beet juice. The subjects (nine competitive cyclists) visited the lab at least five times before the actual experiment even started, to practice taking the time trials until they achieved repeatability of less than 1%.

To reiterate what’s most striking:

  • Performance benefits of 2.8% (6.26 vs 6.45 min) over 4 km and 2.7% (26.9 vs 27.7 min) over 10 miles.
  • This improvement was achieved with just one dose of 500 mL of beet juice, taken 2.5 hours before the event. (Note that this dose is equivalent to 1.6 kg of spinach or 3.1 kg of lettuce!)

They also took other measurements: the amount of oxygen used was the same with and without nitrates, but the power generated was higher with nitrates. Also, plasma level of nitrites was higher after the beet juice, consistent with previous studies suggesting that the beet juice works because nitrates are converted to nitrites then to nitric oxide, which lowers the oxygen cost of muscle contractions.

On another note (further to this previous post):

The subjects also abstained from using antibacterial mouthwash and chewing gum during the supplementation periods since these are known to eradicate the oral bacteria which are necessary for the conversion of nitrate to nitrite.

So what more is there to say, other than “Buy stocks in beet juice companies pronto”? Well, one caveat is that it hasn’t yet been shown that these results can be duplicated in elite athletes. It’s notoriously easier to produce big improvements in less-trained athletes, and these subjects were recreationally competitive. So further studies will be required in elites. But it’s time to acknowledge once again that my initial predictions when I first heard about this research in August 2009 were wrong, wrong, wrong!

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Helmets, head injuries and “risk homeostasis”

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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)

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This week’s Jockology article in the Globe and Mail takes a look at helmets and the slippery concept of “risk homeostasis” — the idea that wearing protective equipment will cause you to take more risks and cancel out any safety benefits:

The message that Mikael Colville-Andersen offered to his audience at the TEDx conference in Copenhagen last November isn’t what you’d expect from a cycling advocate who travels the world promoting urban bike use.

“There are actually scientific studies that show that your risk of brain injuries is higher when you’re wearing a helmet, and that you have a 14-per-cent greater chance of getting into an accident with a helmet on,” he said. “These are not things that we hear about too often.”

With hockey head shots in the news, and revelations that ex-players like Bob Probert suffered from a form of brain damage called chronic traumatic encephalopathy, head protection is a hot topic. But Mr. Colville-Andersen’s controversial anti-helmet crusade offers a reminder that technology and equipment, on their own, can’t keep us safe. We have to consider the underlying factors that influence our risk-taking decisions – and those of the people around us… [READ THE WHOLE ARTICLE]

UPDATE April 11: Lots of e-mails and comments on the Globe site: this is clearly a controversial topic, so I’d like to expand on a couple of points. The truth is that I started working on this article with the idea of presenting the counterintuitive research that Mikael Colville-Andersen discusses in his TEDx talk, showing why helmets are actually a bad idea. But when I dug into the literature, I found that the picture was much more complicated than the way he portrayed it.

There are really two separate questions: physics and public policy. The first is fairly straightforward and asks whether, in the context of certain types of mishaps that sometimes occur on bicycles, a helmet will significantly reduce the severity of your injury. In the lab, we can clearly see that helmets can mitigate the effects of certain impacts. It’s much harder to show that this is the case in the real world, because we can’t have access to “controlled” scenarios of people going head-over-heels with and without helmets. And statistical studies of injury rates are hindered by all sorts of very serious limitations (e.g. we don’t actually know how cycling rates change, let alone traffic conditions, road surfaces, cycling skills, etc.)

Now, one could argue (as many people do) that the lack of crystal-clear epidemiological evidence of reduced cycling-related head injuries is PROOF that helmets don’t work. This is specious. Just because something is difficult to prove doesn’t mean that it’s not true. We can debate where the burden of proof should lie, but my personal assessment of the laboratory data, in combination with the admittedly circumstantial epidemiological data, is that there are certain situations in which I’d be very glad to have a helmet on my head. I certainly accept that other people might look at the same data I looked at and decide that helmets aren’t worthwhile – after all, risk calculation is a personal thing. But those who claim that it’s “proven” that helmets make no difference whatsoever in the context of individual accident scenarios are simply delusional, in my opinion.

Where Colville-Andersen is more convincing is in his public policy arguments, rooted in some of the factors I discuss in the article (risk homeostasis, safety in numbers, etc.). There have been dozens and dozens of studies on cycling injury rates and how they changed (or not) with the introduction of helmet campaigns and laws. My impression after reading through many of these studies: there are more studies supporting the efficacy of helmets than there are null studies, but the results are surprisingly weak and the overall conclusions are equivocal at best. All of the studies are plagued by serious methodological challenges inherent in trying to study this question. There are certainly plenty of studies that forcefully conclude that helmets are either good or no good, and plenty of people who cherry-pick those results in order to claim that the debate is settled one way or the other. But if you open both eyes and look at the totality of the data, I don’t believe there’s enough evidence to reach a conclusion either way.

And that leaves us with some interesting policy debates. If the overall effect of helmets is weak at best, are we justified in imposing a helmet law on children? How many cases of brain damage in Ontario would have to be avoided each year to make such a law worthwhile? One? Ten? 100? 0.1? These aren’t science questions, they’re policy questions. They’re worth debating – certainly, I’m more open to the idea of scrapping helmet laws than I would have been before watching Colville-Andersen’s talk. But as I concluded in the Globe article: based on what I learned from going through all this literature, I’ll still be wearing a helmet when I bike.

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In praise of balaclavas: facial heat loss makes fingers cold

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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)

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Okay, this update isn’t exactly seasonal in the northern hemisphere — but winter will be back in another six months, so tuck this away for future reference. Researchers at the U.S. Army Research Institute of Environmental Medicine (Thermal and Mountain Medicine Division) did a neat little study in the European Journal of Applied Physiology looking at the effect of heat loss through the face.

Basically, 10 volunteers each spent two 60-minute sessions standing in a cold chamber (-15 C) facing into a 3 m/s wind (wind chill equivalent to -20 C). In one session, they wore a balaclava and goggles; in the other session, their face was bare (the balaclava was still on, but pulled down to expose the face, and the goggles were removed. Your face tries to stay as warm as possible, meaning that blood vessels there don’t constrict much even when it gets cold — so there’s the potential to lose large amounts of heat. In addition, there are some direct cues: for example, facial cold exposure triggers the trigeminal nerve, which causes blood vessels to extremities to constrict.

All of this means your fingers and toes are more likely to get cold. And that is, indeed, what they found:

finger temperature with balaclava

The other part of the test was that the subjects had to take their gloves off (while still wearing thin gloves) at multiple points during the test to perform dexterity tests (the Purdue Pegboard and the Minnesota Rate of Manipulation, for what it’s worth). Surprisingly, there were no differences between the trials. Apparently your hands get cold so quickly as soon as you take the mittens off that you no longer get any benefit from having been fractionally warmer a moment earlier.

So the takeaway here: if you get cold hands during winter exercise, keeping your face covered could make a difference. And there’s a bonus insight. Ever since I was a kid, I remember people saying things like “Wear a hat, because the body loses X percent of its heat through your head,” where X was always some enormous number like 90. I’ve always wondered what the actual numbers are. Here’s a passage from the introduction to this paper:

Froese and Burton (1957) provide an example of whole-body cold exposure (-4°C, 2.2 m/s wind) where about half of the resting heat production would be lost from a bare head if the rest of the body was well insulated (5 clo). They (Froese and Burton 1957) estimated that the addition of relatively little insulation (2.4 clo) on the head would restore heat balance, although a higher amount (3.5 clo) would be required if the face remained exposed to cold. If thermal face protection can restore heat balance, extremity cooling would also likely be limited.

So there you go. For that particular set of circumstances, about half of the heat your body produces is lost from the head (including the face). Of course, if you start moving, or if the rest of your body isn’t that warmly dressed, or if the temperature or wind conditions change, then the conclusions change. But still, 50% gives us a ballpark estimate. Neat.

And one final aside: the “standard amount of insulation required to keep a resting person warm in a windless room at 70 °F (21.1 °C) is equal to one ‘clo‘.”

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Hiking the Three Passes route in Nepal’s Everest region

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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)

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Mount Everest viewed from Kala Pattar

We now pause for a short bit of self-promotion: my article in Sunday’s New York Times travel section is now available online. It’s about the trip to Nepal Lauren and I took last December, where we hiked a route called the Three Passes — a way of seeing the Everest region without spending all our time in the traffic jams along the route to Base Camp:

PERCHED on a narrow platform 17,500 feet above sea level, we paused to snack on boiled potatoes and the spicy Tibetan dumplings called momos, and to drink in the view.

We were at the top of the Renjo La, the pass that is the lowest point along a knife-edged ridge separating two valleys. Behind us, looming above a turquoise glacial lake, was Mount Everest. In front of us, an immense stone staircase led down into a valley dotted with roofless stone shelters and the occasional yak — a ribbon of green hemmed in by the soaring gray and white of Himalayan rock and ice.

Stunned into silence by the panorama, we descended the staircase and hiked on in a reverie. It wasn’t until we reached the banks of a fast-flowing river a few hours later that we noticed that the landscape no longer corresponded to the lines and dots on our map. We’d hiked for five hours without seeing another living soul, and, perhaps in part because of our solitude, somewhere along the way had taken a wrong turn…[READ THE WHOLE ARTICLE]

There’s also a nice slide-show accompanying the article, with some pictures from the trip.

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Skipping breakfast leads to lead poisoining?

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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)

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A few months ago, I blogged about the controversy surrounding whether eating breakfast is a good strategy for people trying to lose weight. I (along with expert clinicians like Yoni Freedhoff) am in the pro-breakfast camp, but a few readers offered well-supported arguments against breakfast.

So I’ve been biding my time since then, waiting for a slam-dunk argument — and now I’ve got it! A new study in the journal Environmental Health looked at blood levels of lead in a group of 1,344 children in China. Apparently, it has been shown previously that fasting increases the rate of lead absorption in the gastrointestinal tract. So if you don’t eat breakfast, this daily mini-fast could cause your body to absorb more lead into the bloodstream. Sure enough, after controlling for factors like age and gender, the study found that regular breakfast-eaters (as reported by their parents) had 15% less lead in their blood than regular breakfast skippers.

In all seriousness, this is unlikely to be relevant to anyone who doesn’t have lead paint on their walls or a toy-box full of lead toys. I just thought it was interesting — and it does show that eating patterns and timing do affect how your body processes the food (and heavy metals) that pass through your gut. Overall, the research on breakfast and weight control is still pretty muddled and conflicting. I remain pro-breakfast, but I realize this study isn’t going to win anyone over!

UPDATE April 8: Perfect timing: I just noticed that Peter Janiszewski over at Obesity Panacea has a post on a new prospective study showing that breakfast-skippers aren’t just heavier in a cross-sectional analysis, but also tended to gain the most weight after a two-year follow-up. Still suffers from the same flaws as any non-randomized trial (i.e. the skippers could be the ones who are already battling weight problems), but an interesting finding nonetheless.