Extensibility and stiffness of the hamstrings in patients with nonspecific low 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 department of rehabilitation medicine.

Participants: Forty subjects, a patient group (20) and a healthy control group (20).

Interventions: Subjects laid supine on an examination table with a lift frame, with left leg placed in a sling at the ankle. Straight leg raising, pulling force, and activity of hamstring and back muscles were recorded with electrodes. 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 back muscles measured in an experimental straight-leg raising set-up.

Results: The patient group showed a significant restriction in range of motion (ROM) and extensibility of the hamstrings compared with the control group. No significant difference in hamstring muscle stiffness can be assessed between both groups.

Conclusion: The restricted ROM and the decreased extensibility of the hamstrings in patients with nonspecific LBP is not caused by increased muscle stiffness of the hamstrings, but determined by the stretch tolerance of the patients.