On Wednesday, author Chris McDougall posted a critique of Lance Armstrong's running form on his blog. McDougall is famous for writing Born to Run, the 2009 bestseller about Mexico's Tarahumara Indians and barefoot running. It's hard to overstate how influential that book has become in the two years since it was published, and McDougall deserves a great deal of credit for bringing hugely important ideas about barefoot running to the sport's mainstream.
Born to Run was not without problems, however, and McDougall has elsewhere been criticized for making basic factual errors in his writing. In Wednesday's post, he makes basic errors about biomechanics. McDougall quotes a tweet from Lance Armstrong, who is suffering from plantar fascitis, then writes:
"No surprise. Take a look at his form. Brutal. Wonder why Nike coach Alberto Salazar hasn’t gotten on him to lose that heel strike and unlock that knee?"
Next, he quotes Salazar talking about form in Jennifer Kahn's October 2010 story on Salazar and Dathan Ritzenhein in the New Yorker:
"There has to be one best way of running. It’s got to be like a law of physics. And if you deviate too much from that—the way I did in my career—it can be a big handicap. You show me someone with bad form, and I’ll show you someone who’s going to have a lot of injuries and a short career."
Let's start with McDougall's first comment, that Lance Armstrong's running form is responsible for his plantar fascitis:
In most cases, it's not possible diagnose an injury from looking at two still pictures of a runner's form. In fact, it's hard to diagnose an injury from looking at a runner's form at all, static or otherwise. (Just last week, McDougall criticized people who analyze form on the basis of a limited visual information. Shoe store employees, in this case. Why is it okay when he does it?) The human eye isn't fast enough to see what's happening in real time, and a single picture doesn't tell much of a story. Runners’ feet radically shift position in the milliseconds before ground contact, and it's possible that Armstrong doesn't even heelstrike—neither of the pictures McDougall published show him actually landing. High-speed cameras and force plates are better at teasing apart the links between form and injuries.
What's more, there's not even a solid link between form and injury. There are theories linking high-heeled running shoes with plantar fascitis, but there's nothing to suggest that heelstriking and plantar fascitis are related. In fact, there's just not much credible science linking form to any injury of any kind. So far, the best we can say is that certain types of landing patterns increase vertical loading rates in the lower extremities, and that, in turn, loading rates are correlated with certain types of stress fractures. But it's a weak association, and not one I'd hang my hat on. I'm unaware of any credible research on plantar fascitis and heel striking.*
It's also possible that the footstrike pattern that McDougal favors—landing on the midfoot or forefoot—causes plantar fascitis. As biologist and running blogger Pete Larson recently noted, running barefoot or running in minimalist shoes puts more stress on the soleus and Achilles tendon, both of which connect to the plantar fascia.
Then there's Alberto Salazar's problematic quote about form and the laws of physics. Salazar was one of the best marathon runners in American history, and today he is one of the country's top coaches. But running technique isn't like physics: runners are humans, and humans come in a range of shapes. The laws of physics dictate that we run forward, for example, but there's plenty of variation among even world-record-holding runners. More, we know that runners exhibit radically different form depending on what distances they're running. Elite sprinters and mid-distance runners mostly forefoot strike, but the available data suggest that elite half-marathon runners heelstrike. There is also recent evidence that some people naturally select a heel strike to reduce loading rates, suggesting that there are at least two different best ways of running.
It's important to make a careful distinction about what we do and do not know about running form. McDougall could be right that Armstrong's form is behind his injury. But it's not possible for him to know that it is, and the world doesn't need another person doling out unsolicited, half-baked advice to celebrities. Dr. Phil does enough of that.
*Pete Larson points me to a study linking heelstriking and plantar fascitis. It's not a great study, but it definitely counts as credible research.