This paper assesses a specific connective tissue insufficiency induced hamstring injury occurring in the late swing/early stance phase of sprinting and jumping activities. A literature review related to hamstring injury demonstrates that eccentric muscle action is capable of producing very high forces within the series elastic component (SEC) of the hamstrings in this phase of sprinting. These high forces have been shown to be related to hamstring injury. The utilization of eccentric exercise training regimens can prevent this injury by strengthening the SEC, resulting in a musculotendinous structure theoretically capable of both generating and withstanding higher eccentric and concentric forces.A clinical approach utilizing an eccentric exercise regimen designed to strengthen the hamstrings in the late swing/early stance phase is outlined. A pilot study investigating the exercise indicates it is a valid method of preventing and rehabilitating the hamstring injury in terms of the positions at risk while sprinting, the angular velocities achieved, and the torques produced. J Orthop Sports Phys Ther 1989;10(9):343-349.