The runners were observed on a treadmill machine (跑步机).

　　Sometimes they wore running shoes. Other times they ran barefoot (赤脚的)．

　　Researchers from the JKM Technologies company in Virginia, the University of Virginia and the University of Colorado did the study.

　　They found that running shoes create more stress that could damage knees, hips and ankle joints than running barefoot. They observed that the effect was even greater than the effect reported earlier for walking in high heels.

　　The study appeared in the official scientific journal of the American Academy of Physical Medicine.

　　The other study appeared in the journal Nature. It compared runners in the United States and Kenya. The researchers

　　were

　　from

　　Harvard

　　University

　　in Massachusetts,

　　Moi

　　University

　　in

　　Kenya

　　and

　　the University of Glasgow in Scotland.

　　They divided the runners into three groups.

　　One group had always run shoeless.

　　Another group had always run with shoes. And the third group had changed to shoeless running.

　　Runners who wear shoes usually come down heel first. That puts great force on the back of the foot. But the study found that barefoot runners generally land on the front or middle of their foot. That way they ease into their landing and avoid striking their heels.

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