Electromyographical Study of the Lower Limb Fracture During Sport Activities: Analysis from the Viewpoint of Electromyographical Kinesiology

A variety of avulsion fractures have been reported in young people during sports activities. These usually occur at the insertion or origin of biarticular muscles. In the present study, an attempt was made to analyze the mechanisms of these fractures using electromyography, electrogoniometry, and motion analysis of different sporting activities. Particular consideration was given to the stress imposed on biarticular muscles. Results showed that the avulsion site reflected the "limiting factor joint" of the resultant force output. The greatest stresses were concentrated at the hip joint (origin of the rectus femoris, tensor fascia latae and sartorius) during running, and at the knee joint (insertion of the rectus femoris) during jumping. EMG analysis of the knee extensors during kicking showed that only the rectus femoris exhibited marked discharge and little or no activity was observed in vastus medialis especially in unskilled subjects. The greatest stresses were concentrated at the hip joint and the avulsion site typically occurred at the origin of the rectus femoris.