Humans Could Theoretically Run 40 MPH

Usain Bolt crossed the finish line of the 2009 World Championships in Berlin having just set a world record that still stands today: 9.58 seconds for 100 meters. At his peak during that race, Bolt hit 27.8 mph—faster than most city speed limits.

But here's the wild part: that's not even close to our theoretical limit.

The 40 MPH Question

In 2010, researchers at Southern Methodist University asked a deceptively simple question: what's actually limiting human speed? The answer surprised them.

Dr. Peter Weyand and his team discovered that our muscles can actually generate enough force to propel us much faster than we currently run. The limiting factor isn't muscle power—it's how quickly we can apply that force to the ground.

When sprinters run, each foot only contacts the ground for about one-tenth of a second. During that tiny window, they need to push down hard enough to launch themselves forward. The faster you go, the shorter that contact time becomes.

What's Holding Us Back

The research found that at top speed, elite sprinters only apply about half the force their muscles are capable of generating. The problem? They simply run out of time. Their foot leaves the ground before they can deliver the full force.

Weyand's calculations suggested that if humans could somehow apply force faster—the way some four-legged animals do—we could theoretically hit 35 to 40 mph.

For context, that would mean:

• Outrunning a house cat (30 mph top speed)
• Keeping pace with a charging elephant (25 mph)
• Nearly matching a greyhound (45 mph)

Why We'll Probably Never Get There

The problem is biomechanical. Our Achilles tendons, leg bones, and joints simply aren't built to handle the ground forces that 40 mph running would require. At those speeds, the impact would be roughly five times body weight—every single step.

Evolution optimized humans for endurance, not bursts of speed. We're persistence hunters, built to jog for hours until prey collapses from exhaustion. Sprinting at cheetah speeds was never part of the design.

The Bolt Benchmark

Usain Bolt remains the fastest human ever timed. At 6'5", he was considered too tall to be a great sprinter—conventional wisdom said shorter legs could turnover faster. Bolt proved everyone wrong by combining exceptional stride length with surprisingly quick leg turnover.

Since his retirement in 2017, no one has come particularly close to his records. The 100-meter world record of 9.58 seconds and the 200-meter record of 19.19 seconds both still stand.

So while 40 mph remains a tantalizing theoretical ceiling, 27.8 mph appears to be near the practical limit for the human body as it currently exists. Unless someone figures out how to redesign our legs, Bolt's records might stand for a very long time.