Running a marathon in under two hours has become a holy grail for the sport.
The apparent difficulty of breaking the two-hour mark has led some to suggest that today's distance runners have hit some kind of natural barrier in human ability that may never be overcome.
But researchers from the University of Colorado, Boulder, and the University of Houston suggest the goal is within reach, if the conditions are right, and if runners use special techniques.
They published their results Monday in the journal Sports Medicine.
The closest anyone has even come to the mark is Dennis Kimetto of Kenya, who set a record of 2 hours, 2 minutes and 57 seconds at the Berlin Marathon in 2014.
Since then, few runners have come even close to the time, and running organizations, fitness companies and running magazines have contemplated how the record might be broken, and in some cases, thrown their own efforts behind it.
Nike, for example, announced its Breaking2 initiative in December to help runners beat the time. Nike identified three athletes best poised to achieve the goal: Eliud Kipchoge of Kenya, Lelisa Desisa of Ethiopia and Zersenay Tadese of Eritrea.
Adidas is reportedly working on a similar project, and developing a shoe optimized to beat the time.
"People have been thinking about the magical sub-two-hour marathon for a long time," the study's lead author, Wouter Hoogkamer of the University of Colorado, said in a press release. "Our calculations show that a sub-two-hour marathon time could happen right now, but it would require the right course and a lot of organization."
What do they think it would take?
Start with lighter shoes.
Hoogkamer and colleagues said the runner would need shoes roughly 3.5 ounces lighter than the shoes Kimetto wore in setting the world record — just over 8 ounces each. Hoogkamer and colleagues showed in a previous study that simply reducing the weight of shoes to about 4.5 ounces each shaved almost a minute — 57 seconds to be exact — off a running time.
The design of the marathon course would also play a big role.
The would-be record-breaker would also have to run behind a pack of other runners in a straight line — a technique known as "drafting" that helps reduce wind resistance and propels runners forward — for about the first half of the race.
Drafting is typically seen more in cycling races than in running, where the formation has been known to dramatically reduce the amount of energy each athlete needs to expend.
The researchers cited a study from 1971 that showed an athlete can reduce wind resistance by 93 percent simply by running behind another runner. The current study suggests that reducing wind resistance by a mere 36 percent would be enough to earn a time of 1:59:59 for an athlete already capable of finishing a marathon with 02:03:00, which is three seconds longer than
It would also help if the first 13 miles of the marathon's total 26.22 miles took place on a loop that ran through some kind of environment that protected from winds, like a forest.
The second half of the race should follow a slight downhill slope, and the runners would have to continue using the drafting technique, shaving another 3 minutes off the record. Alternatively a 13 mph tailwind could help push the runners forward enough to cut down the total time.
The researchers note that some of these suggestions are not new, but say they are the first to calculate exactly how much time each measure would save.