1Heiderscheit BC, ¹Thelen DG, ¹Hoerth D, ²Swanson S; ¹University of Wisconsin-Madison; Madison, WI and ²Orthopedic Specialty Hospital; Salt Lake City, UT, USA. heider@surgery.wisc.edu.

PURPOSE: The purpose of this study was to describe the joint and muscle kinematic patterns when an individual injured his hamstring muscles while sprinting. Hamstring muscle strain injuries are common among competitive athletes; however, the mechanisms of hamstring strain injuries are not well understood. For example, there is disagreement on whether the injury occurs during the stance or swing phase of running. SUBJECT: A 30-year-old male (170 cm height; 70.5 kg mass) professional skier injured his right hamstring muscles while serving as a subject in a pilot investigation. The individual did not have a history of hamstring injury, but experienced a left hip dislocation two years prior. Six months following surgical treatment of the left hip dislocation, the subject began a rehabilitation program that progressed to sprinting and plyometric activities by 9 months post-surgery. At 13 months post-surgery, the subject returned to competitive skiing without incident. Seventeen months post-surgery, the subject returned to the clinic to participate in an unrelated pilot investigation. During data collection, the subject experienced a strain injury to the right hamstring muscles. METHODS: Three-dimensional whole body kinematics were recorded (200 Hz) during treadmill sprinting (5.36 m∙s^-1) at a 15% incline. Data were captured for three strides (2 s) prior to an observable indication of the injury. A 14 segment, three-dimensional musculoskeletal model was used with the measured kinematics to estimate joint and hamstring muscle-tendon lengths and velocities prior to, during and following the injury. ANALYSES: Lower extremity joint angles and angular velocities were calculated, as well as musculotendon lengths and velocities of each hamstring muscle. RESULTS: Right hamstring injury was first evident during the early swing phase of the right leg as the subject reached for the treadmill bars to dismount the belt. Review of the kinematics of the lower extremity joints and hamstring muscles did not reveal any causal events in the preceding three strides. Observable changes in the kinematics (decreased peak hip flexion, increased knee extension, increased peak hamstring muscle lengths) occurred during late swing following the injury, ~0.15 seconds after the initial reaction. CONCLUSIONS: The first overt indication of right hamstring muscles injury was a response to the injury during initial swing of the right leg, indicating the injury to have occurred during the preceding stance or terminal swing. Evaluation of the preceding kinematics of the lower extremity joint and hamstring muscles did not reveal a noticeable cause of the injury. FUNDING SOURCE: None.

Copyright 2004 by the American Physical Therapy Association

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