Extensibility and stiffness of the hamstrings in patients with nonspecificlow back pain

Objective: To investigate the extensibility and stiffness of the hamstrings in patients with nonspecific low back pain (LBP). Design: An experimental design. Setting: A university laboratory for human movement analysis in a departmen t of rehabilitation medicine. Participants: Forty subjects, a patient group (20) and a healthy control gr oup (20). Interventions: Subjects laid supine on an examination table with a lift fra me, with left leg placed in a sling at the ankle. Straight leg raising, pul ling force, and activity of hamstring and back muscles were recorded with e lectrodes. Patients indicated when they experienced tension or pain. Main Outcome Measures: The lift force, leg excursion, pelvic-femoral angle, first sensation of pain, and the electro-myogram of the hamstrings and bac k muscles measured in an experimental straight-leg raising set-up. Results: The patient group showed a significant restriction in range of mot ion (ROM) and extensibility of the hamstrings compared with the control gro up. No significant difference in hamstring muscle stiffness can be assessed between both groups. Conclusion: The restricted ROM and the decreased extensibility of the hamst rings in patients with nonspecific LBP is not caused by increased muscle st iffness of the hamstrings, but determined by the stretch tolerance of the p atients.