Close Look at Orthotics Raises a Welter of Doubts

Benno M. Nigg has become a leading researcher on orthotics — those shoe inserts that many athletes use to try to prevent injuries. And what he has found is not very reassuring. 

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Then what, Dr. Nigg asked in series of studies, do orthotics actually do?
They turn out to have little effect on kinematics — the actual movement of the skeleton during a run. But they can have large effects on muscles and joints, often making muscles work as much as 50 percent harder for the same movement and increasing stress on joints by a similar amount.
As for “corrective” orthotics, he says, they do not correct so much as lead to a reduction in muscle strength.