Influence of hip and lumbar extensor strength on lumbar moments during a squat lift: An evaluation of persons with and without low back pain.

BACKGROUND

Individuals with low back pain have been reported to exhibit weakness of the hip and lumbar extensor muscle groups. It is possible that persons with low back pain may perform a squat lift in a manner to accommodate diminished muscular capacity. The objective of the study was to evaluate the influence of hip and lumbar extensor strength on lumbar moments in persons with and without low back pain.

METHODS

Fifty individuals (25 with low back pain and 25 without low back pain) between the ages of 18-50 years participated. Strength of the lumbar and hip extensors was measured using a motor-driven dynamometer. Lumbar and hip extensor moments were quantified during the performance of a squat lift.

FINDINGS: On average lumbar extensor and hip extensor moments during the squat lift were significantly lower in those with low back pain. In addition, lumbar extensor and hip extensor strength were significantly lower in those with low back pain compared to healthy individuals. In persons with low back pain, significant positive associations were found between lumbar extensor strength and lumbar extensor moments (r = 0.40, p = 0.05) and hip extensor strength and lumbar extensor moments (r = 0.48, p = 0.02). Similar relationships were found in the healthy group.

INTERPRETATION: Individuals with low back pain performed the squat lift task in a manner that resulted in reduced lumbar moments. Lower lumbar extensor moments were associated with lower hip and lumbar strength, suggesting that muscular capacity may influence an individual's lifting strategy.