Lumbopelvic kinematics, muscle activation and lumbar spine load sharing in the presence of diminished hip muscle performance

Unrestricted Weakness of the gluteal muscles has been associated with altered lower extremity biomechanics, but the link between diminished hip muscle performance and the lumbopelvic region has not been convincingly established. The objectives outlined in this dissertation were developed to elucidate the effects of diminished hip muscle performance on lumbopelvic kinematics. To accomplish the objectives, experimentations utilizing in-vitro human cadaver lumbosacral spinal specimens and in-vivo lumbopelvic mechanics via three-dimensional motion analysis were conducted.; The purpose of the in-vivo experiment (study #1) was to test the hypotheses that women with diminished hip extensor and hip abductor muscle performance will demonstrate greater rate and range of lumbopelvic motion as well as greater lumbopelvic muscle activity during a single-leg landing task when compared to subjects with stronger hip muscle performance. When compared to individuals with greater hip muscle strength, individuals with diminished muscle strength demonstrated increased lumbopelvic muscle activation, in addition to the greater rate and range of lumbopelvic motion. These findings indicate those with diminished hip muscle performance utilize a different neuromuscular control strategy which further supports the notion of increased spinal loading in weaker individuals.; The purpose of the in-vitro experiment (study #2) was to test the hypothesis that the lumbar facet joint and intervertebral disc will experience greater loading with simulated combined frontal and transverse plane motion than motion in any of the anatomic planes. Loads on the L4-L5 facet joint and L4 intervertebral disc were measured under pure moments and simulated frontal plane pelvic obliquity loading conditions. Results of this study showed facet force was highest in combined loading conditions, whereas there was no increase in intradiscal pressure for the same two conditions. These findings demonstrate the imbalance of load sharing properties between the lumbar intervertebral disc and facet joints, and suggest that musculoskeletal conditions influencing frontal plane spino-pelvic alignment may increase loading to spinal tissues, especially the facet joints.; The results from this dissertation demonstrated that women with diminished hip muscle performance use a kinematic and muscle activation profile that may increase loading on the lumbar spine. Further, direct measurements of spinal loading showed that altered spino-pelvic frontal plane alignment increased facet joint loading. These combined results support the potential for diminished hip muscle performance affecting spinal loading and suggest potential mechanisms for the development of low back problems. Other applications of this research may pertain to training, prevention or rehabilitation.