Date of Award


Document Type

Scholarly Project

Degree Name

Doctor of Physical Therapy (DPT)


Physical Therapy

First Advisor

Susan H.N. Jeno


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


Purpose/Hypothesis: Rotation of the spine is a common movement used to complete daily activities and participate in sports. As a contributing factor to back injuries, the performance of spinal rotation is an important consideration for the rehabilitation of current and prevention of future back injuries. Muscles involved in spinal rotation have been researched, though limited findings exist for one of the largest back muscles, the Latissimus Dorsi (LD). The LD muscle contributes to many movements of the trunk and limbs given its multiple attachment sites including the pelvis, ribs, scapula, and humerus. Influence of the LD on spinal rotation has not been thoroughly researched yet, but results will play a role in the patient's plan of care when treating back pain. The purpose of this study was to increase understanding of muscle activity during spinal rotation and compare muscle activity in fixed and non-fixed positions.

Materials/Methods: Muscle activity was recorded using EMG surface electrodes while subjects performed left and right rotation in both standing and quadruped positions. Ten spinal rotation test positions (standing non~ fixed rotation right/left, quadruped rotation right/left, and standing rotation right and left with arms fixed on the wall at 45°, 90° and 120° of shoulder flexion) were initiated by movement of the pelvis. Using Maximal Voluntary Contraction (MVC) to normalize muscle activity, findings were analyzed for significance at a=.05.

Results: When significant differences were found, the perspective muscle showed increased muscle firing compared to other muscles listed. Significance was found in the right LD between non-fixed right and left rotation and fixed right rotation. During non-fixed right and left rotation as well as fixed right rotation, the right MT showed significance. Left MT showed significant differences were shown when comparing non-fixed right rotation to fixed tight and left rotation. The MT was also significant with non-fixed left rotation compared with fixed right and left rotation. Significance was found in the right ES when comparing right rotation at 45° to left rotation at 45° and 90°, as well as right and left rotation at 120°. Significance was shown with right ES when comparing 1ight rotation at 90° to 1ight and left rotation at 120°. As for the left ES, results were significant when comparing left rotation at 45° to left rotation at 90° and 120°.

Discussion/Conclusion: The findings suggest the LD contiibutes significantly to fixed position contralateral spinal rotation when compared to MT and ES. In fixed positioning, the LD may be mechanically advantaged with a positive length tension relationship to contribute to spinal rotation as established with the trends correlating with increased LD muscle activity during 90 and 120 degree fixed spinal rotation. Whereas in non-fixed positioning, the LD may be at a disadvantaged due to length tension relationship and or the lack of stability from the upper exu·emities. to contribute to spinal rotation compared to ES.

Clinical Relevance: This pilot study looks at the effects of the LD, MT, and ES during spinal rotation. This study is a part of ongoing research to assess the rotational movement strategies in individuals without low back pain. During daily activities, many movements require spinal rotation movements such as putting dishes away in cupboards, taking out laundty, reaching for groceries at the store, and looking behind us when driving to check for upcoming traffic. Our findings suggest clinicians should consider the LD as a possible contributor to spinal rotation. Treatment of patients with back pain should involve thorough examination and specific interventions addressing LD strength and mobility.