A Scientist Correctly Predicted the First Sub-2 Marathon—8 Years Ago. This Is His Next Prediction.
Caio Victor Sousa could make a great living as a psychic if he wanted. The good news for the rest of us is that he decided to go into science instead.
In 2018, Sousa and a group of researchers sat down to attempt to predict the answer to a question that felt almost absurd at the time: when would a human run a marathon in under two hours? Working with historical race data stretching back to 1920, they built a mathematical model and came up with an answer. The year, they said, would be 2026. The runner would most likely be East African, around 27 years old.
On April 26, 2026, Sabastian Sawe crossed the finish line at the London Marathon in 1:59:30. Sawe is Kenyan. He’s 31. So in the world of predictive science, this is just about as spot on as it gets.
“How do I feel about the prediction being right?” Sousa, a PhD, assistant professor of health and human sciences at Loyola Marymount University, and lead author of that 2018 study, told Runner’s World. “Honestly, great.”
The sub-2-hour marathon has long been the sport’s moon landing, a barrier so seemingly ridiculous that serious scientists, Sousa wrote in his study, once called it a “physiological impossibility.” However, with their study, Sousa and his co-authors weren’t merely looking into a crystal ball to predict magic. They were tracking the math of human progress and watching where the stars would indeed align.
The study, published in the Open Access Journal of Sports Medicine, specifically identified the three physiological factors that would define whoever broke the barrier: VO2 max (the maximum amount of oxygen the body can use during intense exercise), running economy (how efficiently a runner uses that oxygen), and anaerobic threshold (the point at which the body shifts to producing lactate). At the elite level, Sousa said, all three are so deeply intertwined that ranking them on which one is more important is almost beside the point. But if you want to know which one matters most for the rest of us who are simply trying to improve our own personal PRs, he has an answer.
"Running economy is the most actionable physiological target," he said. "Improving it allows you to sustain faster speeds at submaximal effort and delays your anaerobic threshold. A better running economy paired with a higher anaerobic threshold will almost certainly translate to a faster marathon, regardless of whether VO2max changes."
As for Sawe's record, Sousa said it can be credited to all of the things above, and a teeny, tiny bit to technology, including Sawe’s carbon-plated Adidas shoes, which can improve running performance by up to 3 percent, the researcher said. And, again, while fancy footwear is cool, Sousa said it's not the story. "The credit," he said, "is 100 percent to Sawe."
The other major factor at play that likely pushed Sawe past the limits we all thought possible is simply the sheer desire to win. Yomif Kejelcha finished in 1:59:41, just seconds behind Sawe, with Jacob Kiplimo running only slightly behind at 2:00:28. That means three men ran faster than anyone ever had, on the same course, on the same morning. "Competitiveness matters too; running with or against someone is a powerful motivator," Sousa said. "Sawe might not have done it without Kejelcha and Kiplimo."
The only bad news, Sousa predicts, is that it's very unlikely for anyone to exceed this showing for some time. "This kind of performance doesn't happen easily," Sousa said. "You need the fastest athletes, healthy and ready to race, but conditions also have to align. Elevation changes, sharp curves, rain, and heat can all slow times." London, he said, had everything needed for a fast race.
As for where the absolute human limit sits, Sousa wouldn't give a specific time, but did offer that he doesn't "think anyone will break 1:55 or 1:56—but if it happens, I'll be thrilled."
There is one area with room for new gains, and that’s with the women’s category. While Sousa noted in his 2018 study that women have increased marathon participation more than men at every level, and have been improving faster for decades, the time gap between women and their male running counterparts is real. That, he explained, is because women have less muscle mass on average, which generally produces lower VO2 max, running economy, and anaerobic threshold, making a two-hour time hard to reach. But still, Sousa is not willing to call it impossible, or even unlikely. He just won't put a year on it. "Marathon performance is also shaped by biomechanical, environmental, and tactical factors," he said. "So it's entirely possible." One day.
For most of us reading this, a 2-hour marathon is something we dream about for other people. But, again, there are plenty of takeaways from Sousa's work for the rest of us—especially the part of bringing all the right pieces together.
"Marathons aren't about the fastest runner," he said. "They're about overcoming a challenge that, ultimately, you face alone. You can have training partners and race-day support, but when you're out there, it's just you—your fast shoes, your nutrition strategy, your accumulated training, your sleep, your habits, your lifestyle, your experience. A marathon time reflects all of that."
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Stacey Leasca is an award-winning journalist with two decades of newsroom experience. Her photos, videos, and words have appeared in National Geographic, Travel + Leisure, Time, Los Angeles Times, Food & Wine, Glamour, Men's Health, Afar, and many more. Stacey also served as an adjunct professor of journalism at the University of Southern California teaching feature writing and visual journalism. She is also a Ph.D. Candidate with a specialty in building resiliency to misinformation.
