This article is from the Aerobics Fitness FAQ, by firstname.lastname@example.org (Robles) with numerous contributions by others.
The heading of overuse injuries is a broad one, into which
the vast majority of exercise-related injuries fall. Generally
overuse injuries are chronic ones, meaning that no single event
causes them (as with a sprained ankle or a broken leg), but a long
series of events over weeks, months, or years of training gradually
weaken or irritate the area in question until exercise
becomes difficult or impossible, or other symptoms appear.
The vast majority of overuse injuries can be avoided by proper
attention to form and technique, appropriate rest, proper equipment
(especially footwear), and gradual increase of exercise frequency,
intensity, or duration.
The best cures for an overuse injury are rest followed by a
gradual return to activity coupled with an awareness of the problem
activity, and appropriate corrective measures (be they more gradual
return to exercise, appropriate strengthening, or avoidance of
certain forms of activity).