Archive for New York City Marathon

running shoes

Posted in Books, Running, Statistics with tags , , , , , , , , , , on August 12, 2018 by xi'an

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!

New York City Marathon snapshot

Posted in Running with tags , , , , , on November 5, 2017 by xi'an

graphics for the New York City marathon

Posted in Running with tags , , on November 1, 2015 by xi'an

Central Park, New York, Sep. 25, 2011As the first runners are starting the race in Staten Island, here are six graphics published in the NYT about the NYC marathon, pointed out to me by my friend Darren. The first one is a great moving histogram that I cannot reproduce here, following the four batches of runners. And the unbearably slow last runner! The second graph is an almost linear increase in the number of women running the race (which, by extrapolation, means that the NYC marathon will be an all-female race by 2068!). The third graph is a square version of a pie chart, which shows that the second largest contingent after the US runners is made of French runners (7%), way above Canadian runners (2.7%). The fifth graph shows spikes in the age repartition of the runners, at 30, 40, 50, and 60: since it is unlikely to be a reporting bias, unless id’s are not controlled when registering, which would be strange given the awards are distributed by five year block age groups, this may be due to people making a big case of changing decade by running the marathon or by runners who take advantage a new age group to aim for the podium. The latest explanation is very unlikely as it would only apply to elite runners and as it should also induce a spike at 35, 45, etc. (Incidentally, I checked the winner’s time in my category, 55-60, and last year a Frenchman won in 2:48:19, which means I would have to run at about the speed of my latest half-marathon to achieve this speed…) The last graph is also quite interesting as it follows the winning times for male and female runners against the current world record across years, showing that the route is not the most appropriate to break the record, in contrast with Berlin where several records got broken.

走ることについて語るときに僕の語ること [book review]

Posted in Books, Running with tags , , , , , , , , , , , on April 19, 2014 by xi'an

The English title of this 2007 book of Murakami is “What I talk about when I talk about running”. Which is a parody of Raymond Carver’s collection of [superb] short stories, “What we talk about when we talk about love”. (Murakami translated the complete œuvres of Raymond Carver in Japanese.) It is a sort of diary about Murakami’s running practice and the reasons why he is running. It definitely is not a novel and the style is quite loose or lazy, but this is not a drawback as the way the book is written somehow translates the way thoughts drift away and suddenly switch topics when one is running. At least during low-intensity practice, when I often realise I have been running for minutes without paying any attention to my route. Or when I cannot recall what I was thinking about for the past minutes. During races, the mind concentration is at a different level, first focussing on keeping the right pace, refraining from the deadly rush during the first km, then trying to merge with the right batch of runners, then fighting wind, slope, and eventually fatigue. While the book includes more general autobiographical entries than those related with Murakami’s runner’s life, there are many points most long-distance runners would relate with. From the righteous  feeling of sticking to a strict training and diet, to the almost present depression catching us in the final kms of a race, to the very flimsy balance between under-training and over-training, to the strangely accurate control over one’s pace at the end of a training season, and, for us old runners, to the irremediable decline in one’s performances as years pass by… On a more personal basis, I also shared the pain of hitting one of the slopes in Central Park and the lack of nice long route along Boston’s Charles river. And shared the special pleasure of running near a river or seafront (which is completely uncorrelated with the fact it is flat, I believe!) Overall, what I think this book demonstrates is that there is no rational reason to run, which makes the title more than a parody, as fighting weight, age, health problems, depression, &tc. and seeking solitude, quiet, exhaustion, challenge, performances, zen, &tc. are only partial explanations. Maybe the reason stated in the book that I can relate the most with is this feeling of having an orderly structure one entirely controls (provided the body does not rebel!) at least once a day.  Thus, I am not certain the book appeals to non-runners. And contrary to some reviews of the book, it certainly is not a training manual for novice runners. (Murakami clearly is a strong runner so some of his training practice could be harmful to weaker runners…)

another road-race in Central Park

Posted in Running, Travel with tags , , , , , , on September 30, 2011 by xi'an

It seems that every Sunday I run in Central Park, I am doomed to hit a race! This time it was not the NYC half-marathon (and I did not see Paula Radcliffe as she was in Berlin) but an 18 miles race in preparation for the NYC marathon. I had completed my fartlek training of 6x4mn and was recovering from a anaerobic last round when I saw some runners coming, so went with them as a recuperation jog for a mile or so. They had done the first 4 miles in 27’28”, which corresponds to a 4’16” pace per kilometer, so I must have missed the top runners. Actually, I think the first runners were at least 4 minutes faster, as they were coming when I left for the last 4mn. (But it was good for recovery!) Checking on the webpage of the race, the winner finished in 1:37’45”, which gives a marathon time of 2:21’40” unless I am confused.