I had the great good fortune to be in Chicago to see Brigid Kosgei set a new women’s marathon world record–in fact, to smash Paula Radcliffe’s record 17 years to the day after she set it. Not only that, I had my camera with me, so I have slow motion video and my analysis to share with you.
First, here’s my video and analysis of what you can see from the side:
Now let’s go a bit deeper.
I’ve written about her form before–most in-depth this past spring in my analysis of the 2019 London Marathon. What I wrote there still held true exactly the same way in this race. Still the large frontal plane pelvis movement with the narrow footfalls.
However today she looked a bit different from the side than she did in London 2019, and radically different than the previous year in London, when I also was on the course and captured high-speed video. Here’s my London 2018 video, cued to start just before she enters the frame:
I had to watch this video a number of times today to be sure it’s the same runner. However certain hallmarks are unmistakable, particularly how she uses her arms.
The differences that stand out starkly to me are that she appears to be sitting back in the 2018 video, and I’m by no means certain that her pelvis is over her foot at midstance the way it clearly was today. Her legs seem overall much more bent–at hip, knee, and ankle–than today. And her back is also quite different–much more neutral in a forward lean, whereas today her back was almost slightly arched throughout the gait cycle, though most noticeably at toe off. That was more pronounced earlier on in the race, but it’s still visible in my video.
In addition, her musculature seems different. It may just be that she’s a little more solid overall now than in 2018–a good thing, surely– but specifically it looks like her glutes and hamstrings are more developed now. And in conjunction with this, I see little sign of the pulled-in abdomen I wrote about as recently as this past spring, and which you can see really vividly in the photo on her Wikipedia page.
Since a pulled-in abdomen is incompatible with really developing and using your glutes and, to a lesser extent, hamstrings, this makes sense.
This is all a quite massive change. It’s pretty common for me to write about runners a few times over the years, and I usually end up just referring to earlier posts because they usually run with consistent form.
So what could explain Kosgei’s transformation?
Here’s the part of the post I hate to write. There’s another difference between her 2018 video and today, and you may have already spotted it too: the shoes. In 2018 Kosgei appears to be wearing normal racing flats, and today she was wearing Nike’s most recent Vaporfly.
The changes I saw in her form didn’t happen just today. Musculature doesn’t change in a day. But I think she was also wearing a version of Vaporflys in London 2019, and I gather she’s been running in them for a while.
I hate to write this for two reasons. The first is that I have so little data, it seems ridiculous to connect the only two data points I have–form change and shoe change–and suggest a causal relationship. I do it, though, while saying there could be a ton of other factors having especially to do with her training that I’m not aware of, because the design of the shoes could promote the kind of form change we see from her.
The second reason I hate to write this is that I hate those shoes. They shut off an important part of the body’s spring mechanism, namely the arch and big toe, and substitute a rigid plate that rocks a runner forward off the tip of her toes. In my experience, you can’t shut off a key part of how the body works in running without paying a price. It won’t happen right away, and the effects will probably vary somewhat from person to person, but the reckoning will come.
Also, they create confusion about the real meaning of the amazing accomplishments we’re seeing–world records broken, the 2-hour marathon barrier falling. Could the runners have done these things without the special shoes? Not knowing puts a damper on the celebration, to say the least.
But, all of that said, and bearing in mind as well that different people respond differently to shoes, it could be that the rocker helped Kosgei move farther forward relative to her feet and activate her extensors better.
Or it could totally have been something else, like a lot of uphill running or different drills, or stopping doing some kind of core work that was messing up her form.
But whatever it was, it worked for her, and she should stick with it. And if she could stop doing that extra little lift of her chest at toe-off, maybe she could even run those faster times–2:11?–she talked about in the press conference afterwards.
Meanwhile, if you think you may be sitting back a bit like Kosgei in 2018, don’t buy those effing shoes. Better movement can be learned, and that lasts a lot longer than any footwear. Here are some of my key hip extension lessons–click the image to try them for free.
Wondering who Jae Gruenke is and on what basis she does running technique analyses? Read this.