The best running shoe may be none at all, US researchers said.
Runners who don't wear shoes may be less likely to do serious injury to their feet, because they hold their feet differently, researchers at Harvard University found.
Writing in the journal Nature, they said runners who wore shoes tended to hit the ground with their heels first, whereas barefoot runners put the balls of their feet down first.
"People who don't wear shoes when they run have an astonishingly different strike," Professor Daniel Lieberman said.
"By landing on the middle or front of the foot, barefoot runners have almost no impact collision, much less than most shod runners generate when they heel-strike.
"Most people today think barefoot running is dangerous and hurts, but actually you can run barefoot on the world's hardest surfaces without the slightest discomfort and pain.
"All you need is a few callouses to avoid roughing up the skin of the foot."
Prof Lieberman and his colleagues at Harvard, the University of Glasgow, and Kenya's Moi University studied runners who had always run barefoot, those who had always worn shoes and runners who had abandoned shoes.
Barefoot runners had a springier step overall, and used their calf and foot muscles more efficiently, they found.
Demonstrations can be seen at http://www.barefootrunning.fas.harvard.edu.
People used to running in shoes should not start barefoot trotting right away, Prof Lieberman cautioned.
"If you've been a heel-striker all your life, you have to transition slowly to build strength in your calf and foot muscles," he said.
But he noted that evolution was on his side.
"Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s," he said.
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