# Humans May Be Biologically Capable of Running 40 MPH

The fastest human alive, Usain Bolt, can run 28 MPH. But a new study proposes a theoretical maximum of 40 MPH for the human body under ideal conditions:

This provides a new twist on the old school of thought that speed limits depended on how much force a runner could exert against the ground. Past studies showed that sprinters can apply up to 1,000 pounds of force with a single limb during each sprinting step, and so researchers thought that humans simply could not push beyond that point.[...]

One-legged hopping produced ground forces greater than those applied during normal running by 30 percent or more, and active leg muscles also generated about 1.5 to 2 times greater force during one-legged hopping. That shows how humans don't exert the maximum possible force during the act of forward sprinting, the researchers say.

Going one step farther, the researchers also found that the "critical biological limit" depends upon how quickly runners can exert ground force while sprinting. Elite runners have foot-ground contact times of less than one-tenth of a second, and max out ground forces within one-twentieth of one second when their foot first hits the ground.

http://www.popsci.com/science/article/2010-01/scientists-investigate-how-break-biological-speed-limits-humans | Photo: US Department of State

Perhaps more interesting is the similar study that showed human beings may have already maxed out their potential to throw a baseball--with the handful of players who have touched 103/104 mph on the radar gun having scraped the upper limits of even theoretical human ability.

Why? The link below explains it better, but the gist of it is that past a certain point, adding muscle and force doesn't help at all; it's the limits of tendons and ligaments that make for the upper limit.

http://www.slate.com/id/2116402/
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Brilliant, Orealy! I was going to make exactly the same point. I especially like how your guess of 70% of the maximum force equals 28 mph as well as (40 mph * sine of 45 degrees).
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Surely hopping can transfer more force simply because the transmission is a right angle, where sprinting is not. Hopping is pushing 100% "up" , while sprinting requires both forward and up (unless you want to do it on your nose). I'm guessing 70 % forward , 30% up.
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