AN ABSTRACT OF THE DISSERTATION OF

Stamatis Agiovlasitis for the degree of Doctor of Philosophy in Exercise and Sport Science presented on August 15, 2007. Title: Three-dimensional Motion of the Center of Mass and Energetic Cost Across a Variety of Walking Speeds: A Comparison Between Adults With and Without Down Syndrome.

Abstract approved:

____________________________________________________________

_________ Jeffrey A. McCubbin

It has been previously suggested that the walking pattern of individuals with Down syndrome is inefficient. This is thought to result from increased instability, particularly in the medio-lateral direction, due to the characteristic joint laxity and muscle hypotonia of individuals with DS. Therefore, this work was an attempt to gain insight into the efficiency of gait in adults with DS by studying their mechanical and metabolic characteristics during treadmill walking. The first study examined the threedimensional motion of the center of mass (COM) and the spatio-temporal characteristics of adults with and without DS at a variety of walking speeds. Fifteen adults with DS and 15 adults without DS walked on a treadmill at six and seven randomly presented dimensionless speeds (Froude numbers), respectively, during which kinematic data were collected. The range of medio-lateral COM position was greater in participants with DS, but the ranges of vertical COM position and anteriorposterior COM velocity did not differ between the groups. Participants with DS walked with faster steps across all speeds. Their step length was shorter only during

slow walking and their step width did not differ from adults without DS. Participants with DS were more variable in medio-lateral and vertical COM position, anteriorposterior COM velocity, and in all spatio-temporal parameters than their controls. The second study examined whether the net VO2 and the net VO2 per unit distance across the same walking speeds are different between adults