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No one checks the weather forecast more obsessively than a marathoner who matches a race. We all dream (like OutsideMartin Fritz Huber said so poetically in a final column) “that perfect meteorological cocktail: the low wind of the 50’s, the dry, wind that follows you magically like a forest sprite.”

But what are the exact ingredients of this ideal cocktail? Numerous studies have been done over the years to try to get the best temperature, but even the world’s leading scientists have failed to reach a consensus. Eliud Kipchoge made his first attempt at a two-hour marathon in 2017, for example, when the initial temperature of 52 degrees Fahrenheit was said to be too hot, according to some calculations, but according to scientists who organized the race. And what about the roles of humidity, wind, and even solar radiation?

a new study in Medicine and Science Sports and Exercise, From a team led by Andreas Flouris of the University of Thessaly in Greece, tries to address all of these questions at once by applying machine learning to a massive database that serves the results of nearly a century of racing. As a result, the knowledge provides a surprisingly practical guide to finding out what you can expect to slow down in a given set of bad weather conditions.

The researchers collected the results of major competitions in the marathon, 10,000-meter, 5,000-meter and 3,000-meter slips, as well as 50K and 20K race rides. These include the Olympics, World Championships, Diamond League track meetings, Golden Label World Athletics road races and other pre-1936 events. ) and well-trained runners (25th, 50th, 100th and 300th places) were compared to the records of the time of the competition. This approach has obvious limitations: time will be influenced by tactical races and other factors such as altitude (e.g., the 1968 Mexico City Olympics). But in a large data set, this gives you an idea of ​​how much the weather in a given year affects the weather.

The four main elements of the weather were air temperature, relative humidity, wind speed, and solar radiation (adapted to cloud cover). These can be considered independently, or in composite indices such as Wet-Bulb Globe Temperature (WBGT), which is a weighted average that takes up four parameters.

There is a wealth of mathematical analysis in the study, using different approaches (including a machine learning method called the resolution tree regression algorithm) to sift through all the data and look for meaningful models. I won’t go through it all (the paper can be read for free if you’re interested in delving deeper into the net), but there are a few quotes I want to take out.

The simplest question is how often athletes do it in good or bad weather. Using the WBGT-based World Athletics rankings, the researchers found that 27% of the races studied were conducted in cool conditions, 47% in neutral conditions, 18% in moderate heat, 7% in high heat, and 1% in extreme heat. We probably expect the number of competitions with unpleasant heat to increase in the coming years, but for now that means you have about 50-50 chances to serve that perfect weather cocktail for any race.

The machine learning algorithm calculated how important each weather parameter was to performance. Not surprisingly, air temperature was the biggest factor, scoring 40 percent of the “feature importance score”. They were followed by relative humidity (26 percent), solar radiation (18 percent), and wind speed (16 percent). According to a study I wrote last year, this suggests that cloud cover is just as important as the lack of wind to walk fast. This, of course, depends on other factors: cloud cover is more important on a hot day than on a cool one, and headwinds will slow you down no matter what the temperature.

As for the mild meteorological spot, the overall conclusion was that a WBGT between 45.5 and 59 degrees Fahrenheit is best. This is interesting because the World Athletics guidelines are “neutral” conditions because they are a WBGT between 50 and 64.4 degrees. To walk fast, the best temperatures seem to be a little cooler than you think. If you dare outside this area, expect a slowdown of about 0.3 to 0.4 percent per WBGT. Of course, few of us have easy access to WBGT measurements. If you look only at the air temperature, the sweet spot is between 50 and 63.5 degrees, which is a little warmer than I expected.

However, there are more nuances when looking at individual events. Shorter races seem to cause less heat: the 5,000-meter temperature peak is 59 degrees; It is 50 degrees for 10,000 meters; and it’s 45.5 degrees for the marathon, which is getting cold. (Running races is another story: it’s a more efficient movement than running, which means more of the energy you burn is lost as heat, which is why most of the heat sickness at elite track meetings is thought to occur to race runners.)

Finally, the practical part. Here’s a chart prepared by the authors for marathons of various paces that shows how much you should expect to slow down depending on air temperature, WBGT, or heat index.

(Photo: Medicine & Science in Sports & Exercise)

These calculations are based on very elite runners who are different from you and me. They move fast, which generates a lot of heat and can lead to cooler temperatures. In contrast, they do not carry much insulation, which may prefer warmer temperatures. Of course, you can make some rough extrapolations from this chart: if the weather conditions suggest that a two-hour marathoner will slow down for two minutes, you can calculate that a four-hour marathoner can slow down in a four-minute front row. “But keep in mind that your mileage may change.”

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