Factors associated with recurrent hamstring injuries.

A history of muscle injury represents a predominant risk factor for future insult in that muscle group. The high frequency of re-injury and persistent complaints after a hamstring strain comprise major difficulties for the athlete on return to athletic activities. Some of the risk factors associated with the possible recurrence of the injury are, in all probability, already implicated in the initial injury. One can distinguish between those events peculiar to the sport activity modalities (extrinsic factors) and other contributing factors based on the athletes individual features (intrinsic factors). For both categories, the persistence of mistakes or abnormalities in action represent an irrefutable component contributing to the re-injury cycle. Additional factors leading to chronicity can come from the first injury per se through modifications in the muscle tissue and possible adaptive changes in biomechanics and motor patterns of sporting movements. We emphasise the role of questionable approaches to the diagnosis process, drug treatment or rehabilitation design. To date, the risk factors examined in the literature have either been scientifically associated with injury and/or speculated to be associated with injury. In this context, quantifying the real role of each factor remains hypothetical, the most likely ones corresponding to inadequate warm-up, invalid structure and the content of training, muscle tightness and/or weakness, agonist/antagonist imbalances, underestimation of an extensive injury, use of inappropriate drugs, presence of an extensive scar tissue and, above all, incomplete or aggressive rehabilitation. Such a list highlights the unavoidable necessity of developing valid assessment methods, the use of specific measurement tools and more rigorous guidelines in the treatment and rehabilitation. This also implies a scientific understanding as well as specifically qualified medical doctors, physiotherapists and trainers acting in partnership.