Author and graduation date: Lyman Baird CONNOLLY, December, 1997

Committee members: Peter Francis (Chair), Robert J. Moore, Robert Pozos

Thesis title: An Electromyographic Analysis of Hamstring Tightness and Low Back Fatigue

Low back pain affects most people at some point in their lives; often it is associated with lifting. Lack of endurance of the back muscles has been implicated as a possible factor in musculoskeletal lower back problems. The goal of this study was to observe if there was a difference in low back EMG median frequency rates between two groups characterized by either flexible or inflexible hamstring muscles. The hamstrings play a role in determining the amount of sagittal motion of the pelvis as a subject bends forward to touch his or her toes. Studies have indicated less anterior tilt of the pelvis with tight hamstring muscles.

The first observation involved recording 100% MVIC of the erector spinae while the subject was executing a stoop lift of 70% lumbar flexion for 5 seconds. The test procedure consisted of lifting with 80% MVIC in 70% lumbar flexion for 30 seconds while in a stoop lift position. The final procedure was a low back EMG recording during toe touch. The hypothesis was that low back erector spinae muscles will fatigue less in the flexible hamstring group.

Independent t-test data determined that the two groups of subjects differed in hamstring flexibility and pelvic tilt during 100% lumbar flexion. The groups did not differ in pelvic tilt during 70% lumbar flexion.

It was concluded that anterior pelvic tilt may not have been affected by the level of hamstring inflexibility of the present groups. Alternatives for future research were discussed.

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