Author: alex

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Lieberman on foot strike and injuries on Harvard’s XC team

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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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Does how you run cause (or prevent) injuries? Everyone has a theory, but no one has much data. Into the breach steps Dan Lieberman, with a new Vibram-funded study of injury rates on Harvard’s cross-country team between 2006 and 2011, just published online at Medicine & Science in Sports & Exercise. He looks at 52 runners — 36 rearfoot strikers and 16 forefoot strikers — all of whom recorded their daily training on an online running log during the study, and whose injuries were precisely recorded by the team’s trainers.

The results?

Approximately 74% of runners experienced a moderate or severe injury each year, but those who habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike.

Now, this is a very interesting and significant result. It also has limitations, which the authors take great pains to detail in their discussion. Probably the most important: this is a retrospective, non-randomized study. That means, for example, that it doesn’t address what happens if a habitual, lifelong rearfoot striker switches to a forefoot strike, which requires stronger calf and foot muscles.

Another point that the authors make is the presence of considerable individual variation. Here’s some of the data:

(The caption reads “Repetitive injuries/10,000 miles; moderate and severe.” Not sure why Harvard is apparently using a Commodore 64 hooked up to a dot-matrix printer to generate its graphics!) Anyway, the point is that some people seem to do just fine with their rearfoot strike, while others are frequently injured with their forefoot strike:

[M]any runners who [rearfoot strike] in shoes do not get injured or get injured rarely even when they train at high intensity. We predict that these runners have better form than those who do get injured: they probably land with less overstride and more compliant limbs that generate less severe impact loading and generate less extreme joint moments… These predictions are supported by several recent studies, and they emphasize the hypothesis that running style is probably a more important determinant of injury than footwear (with the caveat that footwear probably influences one’s running style).

So there you have it. The study’s not perfect, and it doesn’t settle these debates once and for all. But it takes us closer by offering some straightforward data — and that’s how science should work.

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Meb in Skechers vs. Meb in Nikes

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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Meb Keflezighi is an Olympic medallist and a New York Marathon champ. So when he signed with Skechers last summer, observers were… surprised. The company’s new “Go-Run” line promises to make you switch to a mid-foot strike: “The Way You’re Supposed to Run.”

So does it work?

Krista Austin, an exercise physiologist and longtime friend of Meb’s (read about her role in “rebuilding Meb” before his 2009 New York win here), points out this opportunity to compare strides. Here’s Meb in Nikes:

And here’s Meb in Skechers:

Can you see a difference? Any improvement?

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The “Fat Trap” and biological determinism

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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I’ve received a few e-mails asking what I thought of Tara Parker-Pope’s recent New York Times Magazine piece (“The Fat Trap”), which talks about how the body fights off your attempts to make it lose weight. In general, I thought it was a good piece. The basic message I came away with is the same one I hear from people like Yoni Freedhoff: if you want to lose weight — and keep it off — you have to do so using an approach that you’re prepared to maintain for the rest of your life. You can’t go on a diet for six months, lose weight, and then resume your previous diet and lifestyle (or even go halfway back to your previous diet and lifestyle!). Many (perhaps even most) people who are trying to lose weight still see it as a temporary transitional stage. That’s not how the body works, and the more widely that message is spread, the better.

Having said that, a quick note about the apparent “biological determinism” that opposes weight loss. Parker-Pope discusses some of the research by Rupert Leibel’s group at Columbia University, in which subjects are placed on carefully controlled liquid diets to make them gain or lose weight in order to observe what changes take place in their metabolism:

The research shows that the changes that occur after weight loss translate to a huge caloric disadvantage of about 250 to 400 calories… Muscle biopsies taken before, during and after weight loss show that once a person drops weight, their muscle fibers undergo a transformation, making them more like highly efficient “slow twitch” muscle fibers. A result is that after losing weight, your muscles burn 20 to 25 percent fewer calories during everyday activity and moderate aerobic exercise than those of a person who is naturally at the same weight.

I also discuss this research in (plug alert!) my book, Cardio or Weights. And the part Parker-Pope doesn’t mention is that, when you feed people extra calories, exactly the opposite adaptation takes place. In other words, after gaining weight, your muscles burn about 15 percent MORE calories during everyday activity and moderate aerobic exercise. Parker-Pope presents the research as a part of the explanation for why it’s near-impossible to lose weight — but looking at the whole picture, that would mean that it should be impossible to gain weight in the first place! Sure, the barrier is a little bigger when you’re trying to lose weight (20-25% vs. 15%). But the point is, these changes in metabolic efficiency aren’t insurmountable barriers — otherwise no one would ever change weight at all.

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Training one limb to strengthen the other

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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An interesting figure from a new Australian study in the European Journal of Applied Physiology:

The subjects in the study did eight weeks of heavy weight training — using only one leg (their dominant one). As you can see, they dramatically increased strength in both legs. This effect is well known, but I still think it’s pretty cool! The goal of this particular study was to try to figure exactly how this happens, using magnetic pulses to the brain to help assess the role of the nervous system. They did indeed find a significant reduction in “corticospinal inhibition” in both legs, suggesting that the training improves the transmission of the signal from the brain to the muscle, and this improvement applies to both sides of the body.

The point? Well, as the researchers note, it’s something to bear in mind if you have an injury in one leg or one arm. You might be able to keep the injured limb strong without even exercising it. Of course, you have to balance that against the risk of creating physical imbalances. I guess the ideal would be to train enough to increase strength without actually putting on muscle. As the researchers conclude, clinical trials of this approach are needed.

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Des Davila, and learning to increase your carb intake

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)

***

Great in-depth profile of Desiree Davila in the current Runner’s World, leading up to the U.S Olympic Marathon Trials later this month. One passage that caught my eye, referring back to the 2008 Trials:

Davila ran her plan, clocking 5:48 mile splits. At mile 21, she was eight seconds behind eventual third-place finisher, Blake Russell. “And then I just completely fell apart,” Davila says.

It was a fueling issue. As a track runner, competing in the 1500, the 5000, and the 10,000, Davila never had to take fluids. More to the point, she couldn’t. When she tried, everything came up. “I thought, Well, I don’t want to lose breakfast, too, so I’ll just stop drinking fluids on the course.”

That doesn’t work over 26.2 miles. Or at least not for her. She struggled to cross in 2:37:50, for 13th place.

The fueling issue would be addressed—directly. During long workouts, Davila would force herself to drink. Her system, well, rejected it. “It was actually kind of disgusting,” she says. But week after week, her body eventually adapted. “Gross,” she says, “but necessary.”

Every time I write about carbohydrate intake during long endurance races (e.g. here), I get comments from people who say “Well, that may be true for the subjects in that study, but unfortunately that doesn’t work for me. My stomach can’t handle that.” Good thing Davila didn’t just accept that as an unchangeable fact of life.