The etiology of hamstring injury fall into two categories. The sprinting type injury and the stretching type injury. Hamstring injuries affect a wide variety of sports from track & field to soccer, rugby, GAA, gymnasts, and martial arts. Despite recent research into rehabilitation, recurrence and time to return to play, injury recurrence is high. It is thought that the injury mechanism resulting from sprinting is caused by overload of the biceps femoris and semitendonis intramuscular tendon while decelerating, during the terminal swing phase of the gait cycle. Injuries affecting dancers and gymnasts, result in the proximal free tendon(semimembranous) being put in a position of extreme stretch. This can occur at fast or slow movements that involve simulatenous hip flexion and knee extension.