Date of Award

Fall 2019

Document Type

Thesis Restricted

Degree Name

Master of Science (MS)



Committee Chairperson

Dr. Melissa Whidden

Committee Member

Dr. William A. Braun

Committee Member

Dr. David Stearne


Postural balance involves complex coordination and integration of multiple sensory, motor, and biomechanical components. Impairment/distortion of the visual field can affect the ability of the body to maintain balance. Increased influences on balance can result in activation of the motor cortex to enhance the responsiveness of the muscles in the lower body. The purpose of this study was to examine the effects of visual field distortion on muscle activation in the lower extremity during a clinical balance assessment (CTSIB-M). Twenty-one college-aged individuals (age 21.2 ± 2.4 yrs.) completed a stationary balance assessment with three different visual interventions (eyes-open, eyes-closed, and visual impairment). The balance assessment was conducted on a firm surface with each testing period lasting a duration of 30 secs. Surface electromyography was collected throughout each of the testing periods on muscle activation for the soleus, tibialis anterior, and medial gastrocnemius. Analysis revealed a significant increase in sway index for the eyes-closed condition (p<.001) and visual impairment condition (p=.012) as compared to the eyes-open condition. Also, a significant difference was reported between the eyes-closed and visual impairment conditions (p=.038). The eyes-open, eyes-closed, and composite scores for sway index were all significantly different from the age-matched norms (p<.001). No statistical differences were reported between the muscle activation for any of the muscle groups across the three conditions. These observed differences in muscle activation and sway index factors suggest that visual restrictions on interference affects stationary balance but does not directly correlate to an increase in muscle activation.