Hamstring injuries and re-injury are one of the severest lesions that can occur in a number of sports, including soccer, Australian football, track and field events, rugby and, in general, in all sports activities involving sprinting and acceleration. However, it is important to distinguish between the lesions of the three muscles that constitute the hamstring - the biceps femoris, semitendinosus and semimembranosus. Indeed, these three muscles representing the hamstring complex have a very different injury etiology and consequently require different prevention strategies. This fact may explain, at least in part, the high incidence of re-injuries. In soccer, hamstring injuries cause an important loss of time in training and competitions (i.e. on average 15-21 matches per club per season are missed due to hamstring injuries). The high incidence of hamstring lesions has led to a strong research interest in hamstring injury. However, although the research on prevention of such injuries has increased, paradoxically, the epidemiological data do not show a parallel diminution of injuries and/or re-injuries. On the contrary, there is an increase in hamstring injuries.