We already knew that human beings are built for long-distance running, a trait most useful for tiring out prey while out on a hunt. But apparently the human body–or at least the frame–can handle speed, too. As much as 40mph, in fact. According to a recent study, “the stance phase limit to running speed is imposed, not by the maximum forces that the limbs can apply to the ground, but rather by the minimum time needed to apply the large, mass-specific forces necessary”
In other words, “The only limiting factor is not how much brute force is required to push off the ground as previously thought, but how fast our muscle fibers can contract to ramp up that force.” Human beings can generate enough force to run faster, we’re just too slow to make much use of that force.
Take Usain Bolt. Top speed: 27.3mph. At that speed, one leg produces nearly a ton of force in the tenth of a second his foot is in contact with the ground.
The problem? He’s capable of generating even more force, but his foot isn’t on the ground long enough. Or rather, his muscles don’t contract fast enough–keeping his foot on the ground longer would reduce his momentum. If his muscles contracted quicker, he’d be (even) faster.
The animal advantage isn’t in their muscles, however; it’s in their gait. The bending of a dog’s or a cheetah’s spine lets the feet remain in contact with the ground longer without reducing forward momentum. The result? More force is generated.
Of course, most of us probably don’t need to worry about how fast our muscles are contracting. I know I probably just need to keep working on my form and increasing my strength and endurance.
But I do plan to reduce the amount of time my feet are on the ground tomorrow… by taking the day off.