The Effect of a Type and Location of Touch to One’s Own Body on Postural Stability

The primary purpose of this thesis is to inspect the role of one’s body touch on postural stability. Chapter one provides background about body stability and introduces center of pressure measures used for evaluation of postural stability. Chapter two provides a literature review related to maintenance of upright posture, measures of postural stability, the role of vision in control of upright posture, and the role of unilateral and bilateral finger touch in improving postural stability. Further, chapter two describes the purpose of the study and the hypothesis of the two studies. Chapter three describes the design of the two studies, the setting and the study participants. Further, details are given about the instrumentation, the postural stability outcomes used in the reviews, and finger force measurements. Lastly, the statistical analyses used in the two studies are presented. Chapter four describes the results of the first study focused on the investigation of the effect of light and forceful fingertip contact with one’s contralateral shoulder on the body sway while standing upright. Ten healthy subjects participated in this study. Body sway was measured under three conditions: (1) standing with the right index fingertip close to the left shoulder, (2) standing with the right index fingertip lightly touching the left shoulder, and (3) standing with the right index fingertip forcefully touching the left shoulder. The three conditions were performed with eyes open and closed. The mean distance and velocity of the center of pressure movements were measured. Besides, four subjects participated in the pilot study during which we measured the magnitude of the force of the light and forceful touch applied to the contralateral shoulder. Standing with light or forceful fingertip contact with one’s contralateral shoulder was not associated with decrease of postural sway. Standing with eyes closed was associated with the increased body sway in all experimental conditions. The study outcome provided a foundation for future studies exploring ways to enhance balance control in individuals with balance impairments. Chapter five describes the results of the second study focused on the investigation of the effect of bilateral light touch location on postural stability. Ten healthy subjects participated in this study. Body sway was measured when the participant stood on the force platform in four experimental conditions: with arms along the body, and applying bilateral touch to the shoulders, to the head, and the lower back. The four experimental conditions were performed with eyes open and closed. The mean distance and velocity of the center of pressure movements were measured. Standing with a bilateral touch of contralateral shoulders was associated with the smallest body sway as compared to the other three conditions (p<0.05). Standing with eyes closed was associated with the increased body sway in all experimental conditions. The results of the study suggest that the application of bilateral touch to the contralateral shoulders could increase body stability when no external support is available. The study outcome provides a foundation for future studies exploring ways to enhance balance control in individuals with balance impairments. Chapter six describes the study limitations, clinical implications, conclusions and future directions of research