Health Check: Barefoot running
Before we had training shoes, people ran barefoot.
But in the modern world many runners believe that cushioned, comfortable soles will help to absorb some of the impact of running around our parks and streets.
A new trend for barefoot running is emerging. Physical therapists like Rollo Mahon believe that it helps to keep make the body as efficient as possible.
He says that once your feet have toughened up a little then it's much nicer to run without shoes.
Evolutionary biologist Professor Daniel Lieberman, who's fascinated by the idea of barefoot running, went barefoot as he ran around the campus at Harvard University in the United States.
In the laboratory he analysed the gait of barefoot runners, compared with their friends who ran with shoes. The runners with training shoes tended to land first on their heel - sending the high-impact forces up through legs.
Without the protection of shoes, barefoot runners tend to land on their forefoot and take shorter strides - all of which makes their running style "less jarring".
In his paper in the journal Nature, Professor Lieberman hypothesises that this might mean fewer injuries for barefoot runners than those who run with shoes.