Muscle Injuries: Pathophysiology and New Classification Models

Muscle lesions, a high percentage of all acute sports injuries, are frequent in high-demand athletes. Hamstrings, rectus femoris, and medial head of the gastrocnemius are the most commonly involved. They all contain a great percentage of type II fibers, a pennate architecture, and cross two joints and are injured during the eccentric phase of muscle contraction. This chapter describes pathophysiology of acute muscle injuries and, specifically, acute strains. These lesions have a significant impact on the athletes and their teams, but it is often difficult to predict short-term outcome and long-term prognosis. Predisposing factors and mechanisms of injury are described, and a new model of classification is showed. The object is to aid in the prevention, proper diagnosis, and management of these lesions.