Jane Fonda once uttered the phrase "No pain, no gain", but this phrase could actually you to develop a painful stress fracture, a common overuse injury seen in athletes and people who frequently exercise.According to the American Academy of Orthopedic Surgeons (AAOS), stress fractures occur when the muscles are too fatigued to absorb the shock caused when a person increases the amount or intensity of a physical activity too quickly. This transfers the added stress to the bones, which are not equipped to handle the day-to-day impact of high-intensity activity. This can cause the bone to develop tiny cracks, called stress fractures. These fractures are extremely painful--left untreated, it can cause a complete bone break, necessitating surgery.Although stress fractures are more likely to aff