Date of Award

2015

Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)

Department

Physical Therapy

First Advisor

Susan H. N. Jeno

Keywords

Electromyography; Muscle, Skeletal -- physiology; Range of Motion, Articular; Rotation; Spine; Superficial Back Muscles

Abstract

Purpose/Hypothesis: Rotation of the spine, a complex movement that has yet to be fully understood, occurs regularly in activities of daily living (ADLs) and sport performance. Rotation (twisting) of the spine is a contributing factor in low back pain pathology and, by reports, has been associated with up to 60% of all back injuries. One of the largest muscles of the back, the latissimus dorsi (LD), is the only muscle to attach to the spine, pelvis, ribs, scapula, and humerus, and has the potential to impact the spine during many different activities. To date, there is limited research on the activity of the LD during spinal rotation or the effects of the muscle in rehabilitation programs for patients with low back pain (LBP). The purpose of this pilot study was to determine the LD muscle activity throughout spinal rotation during open and closed kinetic chain activities. Three hypotheses were established.

Malerials/Methods: Muscle activity of the LD was recorded by surface electrodes while the subjects performed rotation to the left and right in standing and in quadruped positions. Spinal rotation motion was initiated in the four test positions (standing rotation right/left, quadruped rotation right/left) by movement of the pelvis. Muscle activity was normalized to the maximal voluntary contraction (MVC) of the muscle. Significance was set at α=.05 level.

Results: The ipsilateral LD muscle produced significantly more muscle activity during spinal rotation while in fixed (quadruped) than the contralateral LD muscle (p

Discussion/Conclusion: The results of this study found the LD to be more active during the fixed positional movements. In the right fixed position, the left LD had significantly higher EMG activity than the MT and ES. However, this was not found to be true in the left fixed position. The data showed a significant difference between the activation of the right and left LD, which could be examined further in the future. Although the LD are active without the arms fixed, they demonstrate a significantly greater muscle activity when placed in a quadruped position. When in standing without the upper extremities fixed, other muscles have a greater function in rotation of the spine.

Clinical Relevance: This pilot study highlights the contributions of the LD muscle with spinal rotation and is the beginning of ongoing research efforts to address LD as part of the rotational movement strategy in individuals both with and without LBP. Many everyday movements require spinal rotation with the UEs fixed. Frequently, rehabilitation for LBP includes positions such as the quadruped position. LD is a muscle that should be considered when looking at spinal rotational movement systems.

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