57’32″…

20 years ago…

Argentan half-marathon

Today is the day of the Argentan half-marathon which I will not run this year as I have not yet fully recovered from my Achilles tendinitis. (If running too many days in a row, as I indulged in while in Salzburg, inflammation is back!) Frustrating, as this is my “race of the year” in the Norman countryside. But another break also occurred ten years ago, when I missed the 2009 and 2010 episodes. And somehow this is the “best year” to miss as I am switching to the next age group, V3 or grand-master!, in less than a month, and will thus end up as one of the youngsters in the next race I run! As an indicator, in the 5km trail I ran last Sunday in the Parc, I ended 4th (by one position and 6 seconds!) in my category and 2nd (by three positions and 16 seconds, plus a month!) in the following one.

running shoes

A few days ago, when back from my morning run, I spotted a NYT article on Nike shoes that are supposed to bring on average a 4% gain in speed. Meaning for instance a 3 to 4 minute gain in a half-marathon.

“Using public race reports and shoe records from Strava, a fitness app that calls itself the social network for athletes, The Times found that runners in Vaporflys ran 3 to 4 percent faster than similar runners wearing other shoes, and more than 1 percent faster than the next-fastest racing shoe.”

What is interesting in this NYT article is that the two journalists who wrote it have analysed their own data, taken from Strava. Using a statistical model or models (linear regression? non-linear regression? neural net?) to predict the impact of the shoe make, against “all” other factors contributing to the overall time or position or percentage gain or yet something else. In most analyses produced in the NYT article, the 4% gain is reproduced (with a 2% gain for female shoe switcher and a 7% gain for slow runners).

“Of course, these observations do not constitute a randomized control trial. Runners choose to wear Vaporflys; they are not randomly assigned them. One statistical approach that seeks to address this uses something called propensity scores, which attempt to control for the likelihood that someone wears the shoes in the first place. We tried this, too. Our estimates didn’t change.”

The statistical analysis (or analyses) seems rather thorough, from what is reported in the NYT article, with several attempts at controlling for confounders. Still, the data itself is observational, even if providing a lot of variables to run the analyses, as it only covers runners using Strava (from 5% in Tokyo to 25% in London!) and indicating the type of shoes they wear during the race. There is also the issue that the shoes are quite expensive, at $250 a pair, especially if the effect wears out after 100 miles (this was not tested in the study), as I would hesitate to use them unless the race conditions look optimal (and they never do!). There is certainly a new shoes effect on top of that, between the real impact of a better response and a placebo effect. As shown by a similar effect of many other shoe makes. Hence, a moderating impact on the NYT conclusion that these Nike Vaporflys (flies?!) are an “outlier”. But nonetheless a fairly elaborate and careful statistical study that could potentially make it to a top journal like Annals of Applied Statistics!

semi-marathon d’Argentan [1:27:27, 22/356, 2/65]

As a new anniversary of the beginning of this ‘og, here comes and goes my yearly half-marathon in Argentan, Normandy, which was the 33rd edition of the race and my 19th participation there…

“Ah, le fameux Robert de l’INSEE qui vient faire chier chaque année!”

This was not one of my best races, by far, and the [fake] news that this was going to be the last edition did not help. There were fewer runners than in the earlier races, meaning no protection on most of the route from what seemed like a constant headwind, as I ran by myself from the third kilometre. And I was tired from too much training (and not enough sleeping) the past week in Warwick. Or not enough training the previous week in Vienna. Anyway, this was not a great race and the local V2 [Grand Master] runner who greeted me with the above good-natured apostrophe when I passed him on the second km ended up one minute ahead of me. I could have even stopped at mid-race, were it not for a deficient watch operation, that kept me thinking I could keep with my earlier time [3:39 – 3:50 – 3:59 – 3:53 – 4:00 – 4:28 – 4:11 – 4:06 – 4:04 – 4:07 – 4:24 – 4:39 – 4:01 – 4:12 – 4:05 – 4:14 – 4:03 – 4:16 – 4:17 – 3:58 – 0:25] till the finish line when I found a 4mn difference with the official time! Despite the low participation of 356 runners, and with the support of runners from England, the town of Argentan has vowed to keep the race on for next years, calling for volunteers to man the route and the arrival hall. Till next time, then, hopefully!