Right now, no one on Earth has run a mile faster than 3:43.13. That jaw-dropping time was set by Moroccan legend Hicham El Guerrouj on July 7, 1999 and it still stands untouched. To run that fast, El Guerrouj had to average 55.46 seconds per 400m lap, holding a mind-bending pace of 16.13 mph. Many still regard him as the greatest miler in history, with unmatched form, strength, endurance, and relentless drive. And yet, even he couldn’t dip under 3:40.

So what would it actually take to run a mile in 3:39?

To break 3:40, a runner would need to average 54.6 seconds per lap 0.78 seconds quicker than El Guerrouj’s pace. It might not sound like much, but trimming over three seconds from the world record would be one of the most incredible feats in sports history.

Let’s put that in perspective.

Back in 1954, Roger Bannister became the first man to run a mile under four minutes, a milestone many thought impossible. But shortly after, more runners broke the barrier, and now over 1,500 athletes have done it. However, as performances improve, every second becomes harder to take off. Just 337 runners have gone under 3:55. Drop it to 3:50, and only 63 athletes make the cut. And when we narrow it to sub-3:45? Only three runners in history have ever done it. All Olympic champions. All record-breakers. And even they never touched 3:39.

Meanwhile, the marathon world has seen a recent explosion in record-breaking times, thanks in part to advanced shoes like the Nike Vaporfly and better global training systems. But the mile? It’s barely moved. Why?

Is there less international talent in the middle distances? Have we lost the hunger? Or are we brushing up against the edge of what’s humanly possible?

When we look at a mathematical model comparing world records from 400m to 3000m, a curious pattern emerges. If you apply a flat pace of 60 seconds per lap across events, the best-ever times hover around 20 seconds faster than that benchmark. For the 400m, the theoretical goal is 40 seconds flat. For the 800m, 1:40. And for the mile? Just over 3:40.

The closest any athlete has come to meeting this “minus-20” pace is David Rudisha’s 1:40.91 800m world record 19.09 seconds faster than the 60-second pace. No record in any distance has ever beaten this 20-second threshold. It might just be the invisible line separating the possible from the impossible. And if that’s true, then 3:39 may forever be out of reach.

But records aren’t just about pacing. They also depend on an athlete’s physiology.

Let’s start with VO2 max, the measure of how much oxygen your body can use per minute. Most people fall between 30–40 mL/kg/min. Elite runners? Around 50–60. But the absolute legends? They’re up in the 80s. El Guerrouj reportedly had a VO2 max of 80 proof of his extraordinary aerobic capacity.

Then there’s lactate threshold, the speed at which lactate begins flooding the bloodstream. For top-level milers who run well over 25 km/h, this threshold has to be sky-high. They train for it with brutal intervals, like 400s at near-50-second pace, to build tolerance.

And finally, running economy how efficiently you use energy at race pace. This can’t be pinned down to a single stat, but it’s influenced by everything from stride mechanics to muscle fiber composition. The best milers make speed look effortless, even while clocking sub-56-second laps.

So, could someone combine an elite VO2 max, an insane lactate threshold, and near-perfect running economy?

In theory—maybe. But in practice, after more than two decades without progress beyond El Guerrouj’s mark, the idea of a 3:39 mile looks like science fiction. For now.