HUMANS living millions of years ago were endurance runners, but how did they do it without air-cushioned soles? The secret might have been to land on the balls of their feet.
Daniel Lieberman at Harvard University and colleagues compared the gait of endurance runners in the US and Kenya and found that more than two-thirds of those who grew up running barefoot or had trained themselves to do so as adults ran on their tiptoes, landing on the balls of the feet first (Nature, ). The trend is unusual: 80 per cent of endurance runners land heel-first.
The result suggests that our ancestors were toe-runners. This may simply reduce pain. In racetrack tests, the team showed that the impact on the foot is seven times as great in heel-first runners. 鈥淚t鈥檚 like someone hitting you on the heel with a hammer three times your body weight,鈥� says Lieberman.
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This is because the collision force depends on how much mass comes to a dead stop, Lieberman says. In a heel-first runner, the lower leg stops suddenly on impact in addition to part of the foot.
