Acute effects of hamstring-stretching exercises on the kinematics of the lumbar spine and hip during stoop lifting

BACKGROUND: Hamstring-stretching exercises are frequently used to change lumbar spine and hip movements in the clinic. However, little research into the effects of hamstring flexibility on lumbar spine and hip movements during lifting tasks has been reported. OBJECTIVE: We investigated effects of hamstring-stretching exercises on the kinematics of the lumbar spine and hip during stoop lifting. METHODS: We recruited 16 males with a reduced range of motion (ROM) in active knee extension (AKE). The angle of the lumbar spine and hip was measured during stoop lifting using a 3D motion-capture system. The ROM of AKE and the angle of the lumbar spine and hip during stoop lifting between pre- and post-stretching were analyzed using a paired t-test. RESULTS: We found that hamstring-stretching exercises increased the ROM of AKE significantly. After hamstring-stretching exercises, there was a significant increase in hip flexion and decreases in both lumbar flexion and the lumbar/hip flexion ratio during the preparation phase of stoop lifting. In the lifting phase, only the movement range of the hip was increased significantly. CONCLUSIONS: Hamstring-stretching exercises may be useful for decreasing lumbar flexion and increasing hip flexion in people who perform repetitive stoop lifting in the workplace or during daily activities.