Gastrocnemius injury during running: a case report.

Incidence rate of running related injuries is high but forces acting on the body during injury are hardly known. During a data collection session in the investigator's laboratory, one subject sustained a medial gastrocnemius muscle strain injury while running across a force platform. This case report aimed to investigate the causes of this acute running injury by comparing the running speed, external forces, joint kinetics and kinematics, and muscle-tendon complex length of the injured trial to five preceding noninjured trials. The injured trial was characterized by faster running speed, higher external loading rate, increased muscle-tendon complex length and shortening rate, and indifferent patterns in ground reaction forces, joint angles, moments and powers. Both kinetic and kinematic data suggest that the injury occurred during the early stance phase, which is in agreement with the subject's description. These data are unique and invaluable to the understanding of internal and external loads during acute traumatic running injuries. The findings suggest that the injury occurred soon after touchdown and may be caused by a faster than usual running speed and inappropriate body posture at touchdown, which lead to altered muscle length and actions to attenuate impact shock.