| Disorders of the lumbar spine are highly prevalent and impose a large socioeconomic burden. The lumbar multifidus (LM) is a muscle which serves a unique stabilizing role in the lumbar spine. Neuromuscular impairments in LM morphology and function have been reported to result from lumbar spine disorders, and lumbar stabilization exercises are commonly prescribed to address these impairments. Therefore, the purpose of this dissertation was to enhance the understanding of stabilization exercise and the role of the LM among nonoperative and postoperative populations with lumbar spine disorders.;A preliminary step in this process was to systematically review the literature with respect to the rater reliability of quantitative estimates of trunk muscle morphology and function using rehabilitative ultrasound imaging (RUSI). Seven-hundred fifty-six studies were considered with 24 studies included in the review. The results indicated that RUSI measures of trunk muscles demonstrate good rater reliability.;The construct validity of prognostic factors thought to predict a favorable clinical outcome for patients with LBP undergoing a lumbar stabilization exercise program was then investigated. A cross-sectional design was used to examine the relationship between the factors and RUSI measures of LM activation among 40 individuals with nonspecific LBP. The construct validity of the prognostic factors was supported by the univariate and multivariate relationships identified between the prognostic factors and LM activation, with the presence of the prognostic factors identifying those individuals with greater functional impairments.;In the primary study, we performed a parallel group randomized clinical trial investigating the efficacy of two exercise approaches following lumbar disc surgery as well as the relationship between change in LM muscle function and clinical outcome. Thirty-eight subjects were randomized to receive motor control exercises emphasizing LM function or general trunk stabilization exercises initiated after 2 postoperative weeks. Study outcomes included pain, disability, global change, and sciatica frequency and bothersomeness. No significant between group differences were identified. However, there was a relationship between improved LM function on the side of surgery and global improvement. This finding may highlight the importance of maximizing LM function following lumbar disc surgery. |
