Author: alex

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Decision fatigue and workout planning

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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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John Tierney has an interesting article in New York Times Magazine about the concepts of “decision fatigue” and “ego depletion” — the idea that the simple act of making decisions, no matter how seemingly trivial, uses of a finite store of willpower. The idea seems intuitively obvious, but the studies he describes are fascinating and unexpected.

For example, prisoners appearing before Israeli parole boards have a 70 percent chance of getting parole if they appear first thing in the morning, but just a 10 percent chance if they appear late in the day: the judges are tired of making decisions, and react unconsciously by sticking to the default option. Lots of different factors affect decision fatigue, including glucose levels in the brain — so the chance of parole drops to 20 percent by midmorning, then rises to 65 percent after the midmorning break, during which sandwich and fruit is served to the judges. Just before lunch, probability is back down to 10 percent, then back up to 60 percent immediately after lunch, and so on.

It’s a long article, and I don’t want to oversimplify by summing up — but this is the passage, near the end, that I found interesting in the context of exercise:

“Good decision making is not a trait of the person, in the sense that it’s always there,” Baumeister says. “It’s a state that fluctuates.” His studies show that people with the best self-control are the ones who structure their lives so as to conserve willpower. They don’t schedule endless back-to-back meetings. They avoid temptations like all-you-can-eat buffets, and they establish habits that eliminate the mental effort of making choices. Instead of deciding every morning whether or not to force themselves to exercise, they set up regular appointments to work out with a friend. Instead of counting on willpower to remain robust all day, they conserve it so that it’s available for emergencies and important decisions.

I think this is a really important point. Strangely, I’ve found it’s much easier for me to stick to a routine where I run every day than to run six or five or four days a week. In terms of my current fitness goals, six days would be plenty and possibly even preferable to seven — but as soon as you introduce that element of choice, every morning suddenly gets much more complicated. Should I take my day off this morning? How tired am I? Is it going to rain? How do I expect to feel later in the week?

When I was training more seriously, a periodic rest day was much more important in order to get adequate recovery — but even then, I found it much easier to schedule a regular rest day (I took every second Monday off) than to make those decisions on a day-to-day basis. It wasn’t a question of being too obsessive to take an unplanned day off — it was simply too much mental effort to have to decide every morning “Am I running today?” There’s a great passage in Once a Runner about that idea (unfortunately I don’t have my copy here, or I’d quote it), how you have to make the decision about what you’re going to do, then close the book and just do it, rather than revisiting the decision every time it gets hard, or every time you wake up in the morning. (Of course, you still have to allow a certain amount of flexibility: sometimes it really is smarter to take an unplanned day off — but that’s different from having a regular weekly day off that can be taken any day of the week.)

When people ask me for advice about planning an exercise program, that’s one of the things I emphasize. Being flexible and fitting in exercise when it’s convenient may sound good in theory. But for me, at least, my will power isn’t strong enough to do that on a regular basis. Better to make the decision in advance, then just follow my own orders when it’s time to workout.

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Cryosaunas enter the realm of real sports science

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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, I admit I enjoyed making fun of the “cryosauna” last fall, after it emerged that Alberto Salazar had arranged to have one shipped to New York so that Dathan Ritzenhein could use it before the New York Marathon. With the manufacturer promising “tighter, healthier skin,” “increased libido,” and “stronger, fuller hair,” the concept was ripe for a few jokes — especially since there was no actual science supporting its use for athletes.

But now I have to get serious, because a legit study has been published, funded by the French Ministry of Sports (and not by the manufacturer — actually, it’s a German company that made the cryosaunas used in the study). The full text is freely available via this link. The study had 11 trained runners do a pair of 48-minute hilly treadmill runs (i.e. including enough downhill to trigger muscle damage and soreness) separated by at least three weeks. After one of the runs, they were given three minutes of whole-body cryotherapy at -110 C immediately after, and then again once a day for the next four days. After each cryotherapy session, blood tests were taken to measure a bunch of inflammation and muscle damage markers. After the other run, they followed the same protocol, except replacing the daily bout of cryotherapy with 30 minutes of passive sitting.

One thing to emphasize: this study appears to have been very carefully executed. Throughout the study, the subjects were told exactly how much they were allowed to run, and they weren’t permitted to use anti-inflammatories or other recovery aids. They also controlled food and drink intakes.

The results? They’re pretty complicated because they tested a lot of things. For most of the markers, there was no difference. But there were three key differences:

  • C-reactive protein, a marker of muscle damage, stayed almost unchanged in the cryotherapy group, whereas it spiked after 24 hours in the control and was still elevated three days later.
  • Interleukin-1beta, a pro-inflammatory cytokine produced after strenuous exercise, was slightly suppressed by cryotherapy (though not by much, if you look at the data below).
  • Interleukin-1ra, an anti-inflammatory cytokine inhibitor that counteracts the pro-inflammatory cytokines, was temporarily but significantly enhanced immediately after the post-exercise cryotherapy session.

Here’s what the data for those three factors looked like (WBC is whole-body cryotherapy; PAS is passive recovery):

So does this settle any debate? Well, there’s always a big gap between seeing a minor change in some blood test and translating that to a functional benefit for an athlete. Does cryotherapy permit a better next-day or day-after-tomorrow workout? We don’t really know. On a more general level, do the benefits of (hypothetically) more rapid recovery outweigh the (hypothetical) disadvantages of suppressing the inflammatory signals that tell your body to adapt and get stronger? Again, we don’t really know — that’s still in the realm of coaching art, not science. Is a massively expensive cryosauna any better than a bathtub with a few blocks of ice thrown in? Still don’t know.

But having said all that, this study does suggest that we can move the cryosauna from the category of “wacky techno-schemes that sound like you mail-order them from the back of a comic book” to “serious recovery modalities that are as likely as anything else we currently rely on to work.” (Though I’m still reserving my judgement on the “better hair” claims.)

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“Fat and fit” and the Edmonton Obesity Staging System

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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 quick follow-up to my post from a few days ago about the study suggesting that being overweight as you age doesn’t predict longer life after all. Several people have pointed out the just-released studies on the Edmonton Obesity Staging System (press release here; one of the abstracts here), which found that:

Obese individuals with no, or only mild, impairments were found to have the same mortality risk as lean individuals, and were less likely to die from cardiovascular causes.

Does this mean that being a little bit overweight doesn’t hurt, and may even help — contradicting the Loma Linda study I wrote about earlier? Not exactly. The studies are looking at two different things.

The Edmonton Obesity Staging System (EOSS) is summarized in this graphic. Basically, Stage 0 means you’re overweight but have no signs of any related risk factors like hypertension, impaired fasting glucose, elevated liver enzymes, etc. Stage 1 means you’re overweight but only have subclinical indications of any of these related risk factors. Only once you get to Stage 2  do you start dealing with problems like hypertension and Type 2 diabetes.

What the latest study found is that being Stage 0 or 1 didn’t predict earlier death than having “normal” weight. This is entirely consistent with the last two decades of research by Steven Blair (one of the authors of the new study) on “fatness versus fitness.” The basic gist is that fatness, on its own, isn’t what kills you. If you’re overweight but can avoid the risk factors commonly associated with being overweight — and the main way to do that, Blair argues, is to be aerobically fit — then your health outcomes are no different than the average person.

The Loma Linda study, on the other hand, didn’t separate out the “fat and fit” people from the “fat and unfit.” They just looked at the overall results based on BMI, and found that those who were overweight were more likely to die earlier. This isn’t unexpected — because let’s face it, those who are overweight are more likely (but not guaranteed) to have associated risk factors like hypertension and diabetes.

To make a slightly silly analogy, we could say that the Loma Linda study is equivalent to showing that people who buy cigarettes are more likely to get cancer. Of course, this doesn’t mean that the act of purchasing them gives you cancer — it’s perfectly possible to buy cigarettes and not smoke them. But those who buy them are generally pretty likely to smoke them. (NOTE: this was the simplest analogy I could think of — I’m not equating obesity to smoking, not am I saying that being “fat and fit” is as rare as buying cigarettes and not smoking them!)

So why does this matter? Well first, I should emphasize that I think Steven Blair (and Arya Sharma and their colleagues)’s message is very important. Our public health messages should focus on fitness, not fatness. So — as I concluded my previous post by saying — I don’t think the Loma Linda results “prove” that being overweight is a ticking time bomb. Instead, it’s the opposite message that I’m emphasizing: that not being overweight isn’t something you should worry about. The earlier studies suggesting that being overweight made you live longer led to media articles like Margaret Wente’s infamous “Get fat, live longer” — and that’s misleading. The Loma Linda study corrects that mistake.

And on that note, I should point out that same false comparison is being made to some degree with the new study. For example, the passage I quoted above: “Obese individuals with no, or only mild, impairments… were less likely to die from cardiovascular causes [compared to lean individuals].” (Or even worse, this press release that sums up the study as finding that “being fat can actually be good for you.”) This is a false comparison. They’re cherry-picking the subset of overweight people who have no clinical signs of any risk factors like hypertension or blood sugar problems, and comparing them to all lean people, however healthy or unhealthy. This doesn’t tell us that it’s “good” to be overweight — it tells us that (duh) it’s good not to have diabetes, high blood pressure, arthritis and a messed-up liver!

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Carbs and insulin vs. reward theory as the cause of obesity

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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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For those interested in the cause of obesity, a lengthy post by blogger and neurobiologist Stephan Guyenet is rocketing around the Internet. After a rather testy exchange with Gary Taubes at the Ancestral Health Symposium (which culminated with Taubes offering Guyenet this no-so-friendly advice: “I would just recommend in the future you should pay attention to populations that might refute your hypothesis rather than just presenting populations that support.  That’s always key in science.“), Guyenet decided to write a detailed dissection of Taubes’s carbohydrate theory of obesity, explaining why it’s “not only incorrect on a number of levels, but may even be backward.”

Here’s Taubes’s own statement of the theory in question, as quoted by Guyenet from Good Calories, Bad Calories:

This alternative hypothesis of obesity constitutes three distinct propositions.  First, as I’ve said, is the basic proposition that obesity is caused by a regulatory defect in fat metabolism, and so a defect in the distribution of energy rather than an imbalance of energy intake and expenditure.  The second is that insulin plays a primary role in this fattening process, and the compensatory behaviors of hunger and lethargy.  The third is that carbohydrates, and particularly refined carbohydrates– and perhaps the fructose content as well, and thus perhaps the amount of sugars consumed– are the prime suspects in the chronic elevation of insulin; hence, they are the ultimate cause of common obesity.

Guyenet’s post is an interesting read, and it certainly raises some questions about Taubes’s reductionist approach to obesity (which I’ve criticized in previous posts). It should be noted that Guyenet himself has a Grand Theory of Obesity, which he dubs the “food reward” theory. It basically argues that modern foods trigger reward behaviour in our brains without the accompanying satiety signals that traditional foods would offer. To his credit, he’s more circumspect about trumpeting the powers of his theory: the post I linked to is titled “Food Reward: a Dominant Factor in Obesity.” No doubt that Taubes would have said “the Dominant Factor…” 🙂

Still, my overriding sense is that scientists (and journalists, for that matter) with Grand Theories rapidly become unable to critically evaluate data that conflicts with their theory. Personally, I think it’s highly unlikely that we’ll find a single dominant factor that explains the dramatic rise in obesity over the last few decades, and the endless search for that one magic bullet distracts us from the obvious contributing factors that we already know about.

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Foot strength for runners

THANK YOU FOR VISITING SWEATSCIENCE.COM!

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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Also in today’s Globe, I have a very short piece about foot strength for runners:

During a one-hour run, your feet push off the pavement about 10,000 times – enough of a workout to build some pretty impressive foot muscles, you’d figure.

“Considering the countless miles that runners put in, most think that they have very strong feet,” says Matt Ferguson, the president of Vancouver-based Progressive Health Innovations. “And they do – but only for one motion.”

Running does wonders for the muscles involved in plantar flexion – pointing your toes toward the floor – but leaves a host of other small muscles throughout the foot and ankle weak. The result is an increased risk of common running injuries like plantar fasciitis, shin splints, Achilles tendon problems and even ankle sprains… [READ THE REST OF THE ARTICLE]

The article takes a brief look at a few difference ways of strengthening your feet, ranging from barefoot running to old-school soup-can-in-a-sock exercises to fancy new gadgets like the AFX Ankle Foot Maximizer.