"Orthotics" is the name for the shoe inserts many athletes use in an attempt to prevent injuries. But analysis shows that, while shoe inserts or orthotics could theoretically be helpful as a short-term method of preventing injury, it is not entirely clear how to make inserts that work.
The notion that orthotics correct mechanical-alignment problems does not hold up to study. However, orthotists argue that this does not take into account the benefits that patients perceive; according to them, it does make patients feel better.
According to the New York Times:
"... [W]hat ... 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 ... they do not correct so much as lead to a reduction in muscle strength."