Neurophysiologic influences on hamstring flexibility: A pilot study

Objective: To examine the potential contribution of neurologic influences on hamstring length during passive range of motion. Design: Prospective study. Settings: Academic sports medicine center. Patients: 15 subjects undergoing arthroscopic surgery for unilateral knee injuries without previous injury to the contralateral knee. Interventions: Subjects received: 1) spinal anesthesia with bupivacaine, 2) epidural anesthesia with lidocaine, 3) general anesthesia, or 4) femoral nerve block of injured leg only. Main Outcome Measures: Noninjured leg popliteal angle preoperatively, intraoperatively under anesthesia, and postoperatively after recovery from anesthesia. Results: The overall mean popliteal angle was 132.5 +/- 3.1 degrees preoperatively, 134.31 +/- 11.6 degrees intraoperatively, and 130.7 +/- 10.2 degrees postoperatively. Overall, the intraoperative angle was significantly greater than the postoperative angle (p = 0.02). The mean change in popliteal angle was 8.1 +/- 2.2 degrees (Group 1), -0.4 +/- 1.9 degrees (Group 2), 0.9 +/- 1.4 degrees (Group 3), and -2.4 +/- 3.8 degrees (Group 4). There was no significant change in pre- to postoperative popliteal angle in relation to postoperative pain. Females had a greater mean popliteal angle (139.84 degrees) compared with males (128.84 degrees) (p = 0.04). Clinical Relevance: Understanding the neuromuscular influences on muscle flexibility will assist in the development of new rehabilitative and injury preventative techniques. Conclusion: The present pilot study implicates neural contributions to muscle flexibility. Further studies are needed to delineate the relative contributions of neural and muscular components and to facilitate new techniques in the rehabilitation and prevention of injury.