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Photo: Drew Geraets |
This year, however, many participants were
disappointed with their times. Warmer
than average temperatures and clear, sunny skies caused many runners to finish
well back from their goals. Since
several runners that I coach or advise ran the race, I was curious to see how
much of an effect the temperature had on their finish times. So, as I often do, I started crunching some
data.
Fortunately, I was able to stand on the shoulders
of some Big Running Data giants—a
2012 scientific paper by Nour El Helou and other researchers in France
already laid the groundwork for disentangling the effects of climate on
marathon race times. In their paper, El
Helou et al. analyzed ten years' worth of results from six World Marathon
Majors (London, Berlin, Paris, Boston, Chicago, and New York), resulting in a
data set of 60 marathons. These totaled
almost 1.8 million marathon finishers.
El Helou et al. ran statistical analysis on each year's results, trying
to find the correlation between ambient temperature during the race and the distribution
of the finish times.
El Helou et al.'s methods
Because El Helou et al. (correctly) hypothesized
that temperature would have varying effects on runners of different abilities,
they analyzed several levels of performance for the top one, 25th, 50th, and 75th
percentiles of male and female finishers.
So, for example, if the 2010 Chicago Marathon had 21,000 male finishers,
the authors looked at the finish time for 210th place—that's the "one
percentile" time. This marker is
more useful than looking at the winning time or 10th place, because those can
be affected by things like the quality of the elite field, the tactics employed
by the lead pack, and so on. After
extracting the various levels of performance for the 60 marathons in the data
set, El Helou et al. then consulted meteorological records to find the ambient
temperature midway through each of the 60 races.
Doing regression analysis allowed El Helou et al.
to correlate the ambient temperature with the distribution of finish times. The broad trend in the results was not
surprising: marathon times are slower when temperatures are too hot, and they
are also slower when temperatures are too cold.
What was surprising, at least
to me, was the optimal temperature for marathoning. El Helou et al.'s data robustly shows that
the ideal temperature for running a marathon is pretty chilly—39 degrees Fahrenheit
(3.8° C) for a 2:40 marathon! Race
times follow a parabolic curve, slowing significantly on either end of an
optimal temperature.
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