Last week a Kenyan man broke the world record for running a marathon. Dennis Kimetto ran the Berlin Marathon in two hours, two minutes and 57 seconds, beating the previous world record holder by 26 seconds. The feat set speculation abuzz (once again) that someday, someone might run a marathon in under two hours.
Of course, not everyone is convinced that's within reach. Last year, when Wilson Kipsang set the previous record by running finishing Berlin’s 2013 race in 2:03:23, Scott Douglas wrote in Runners’ World: "Sorry to be a nattering nabob of negativity, but a sub-2:00 marathon on a record-eligible course won’t happen for many, many years."
The issue is that each record is harder to beat. To update Douglas’s calculations using Kimetto’s times: A marathon is 26.2 miles and Kimetto was able to shave 0.99 seconds off each mile. But to reach sub-2:00, a runner would have to beat Kimetto by 177 seconds. That’s a whopping 6.76 seconds per mile. Kyle Wagner for Deadspin explains:
To a casual runner, it doesn't sound like a whole lot, just under seven seconds per mile over the course of a marathon. You can drop or gain whole minutes from mile to mile in a 10k. But at elite marathon pace, already run at sub-five-minute speed, asking for even a few seconds per mile can break a race, or a runner.
Still, it could happen eventually, given improvements in training, course design and some luck of genetics. Wagner asked David Epstein, author of The Sports Gene what the perfect long-distance runner would look like:
"You'd start with really long legs," says Epstein, "a giant chest cavity with huge lungs with surface area to put a lot of oxygen into the blood, a stiff and long Achilles tendon, a massively strong heart, tremendous blood volume." And then you come to finer points, like distal elongation (where the lower legs are even longer than the upper legs), or tiny calves and ankles that don't weigh down the pendulum-like motion of running.
The next record-setting marathoner could well be a Kenyan man. A study by Japanese researchers shows that Kenyan athletes have highly elastic tendons (though Wagner pointed out that the researchers compared the athletes to non-athletes, which makes the findings less surprising). Those Kenyan atheletes also have very thin lower legs.
A woman breaking the record is less likely, despite the theory that women are better at longer distances. The fastest women are very fast, but there are comparatively fewer of them that run as quickly as the fastest men.
If the record is broken, the odd, unpredictable influence of luck will certainly be at play. Kimetto began running competitively a few years ago and is 30 years old. But as we get better at keeping elite athletes healthy for longer, more athletes in their prime can try.