Seated balance during pitch motion with and without visual input.

The study of seated balance and postural control, specifically in relation to wheelchair propulsion, has been an area of interest for quite some time. In biomedical and rehabilitation research this has led to the potential of treatment and prevention of spinal cord and musculoskeletal injuries. To date, little study has been done which analyzes the activity of lower trunk muscles for seated balance, as opposed to upper limb and shoulder muscles. For the purpose of this study, motorized rotational movement in the forward and backward directions was simulated and the corresponding lower back and abdominal muscle activity was recorded by surface electromyography (EMG). A comparison of how muscle activity was affected by visual input was also conducted. This pilot study was performed on two healthy individuals, recording two of their abdominal muscles, and two lower back muscles. Electrodes were placed on the right and left rectus abdominis, external oblique, thoracic erector spinae, and lumbar erector spinae. Each trial consisted of twelve randomized tests that were performed twice on each subject. The results showed that the speed of rotational motion was the dominant factor in abdominal muscle activity. The results also suggested that motion of the subject with respect to the visual display had an inhibitory effect on the motion perception. Furthermore, challenges to wheelchair patients on a slightly rough terrain were highlighted. Finally, the results also suggested that visual effects during rotational motion had a small effect on the subject, which was possibly caused by placing focus on something else rather than on balance issues.