It is difficult to think of any activity that does not require some degree of turning. Despite the prevalence of turning in daily activities and the challenge it poses to mobility-impaired individuals such as those with Parkinson’s disease, there is far less known about the multi-segmental control of turning than the control of standing and straight walking especially in elderly individuals and patient populations. The purpose of this thesis was to examine the coordination of body segment reorientation in healthy older adults and people with Parkinson’s disease (PD) during on-the-spot turns when standing and turns initiated when walking. The coordination of body segments was examined for small and large magnitude turns in both populations. PD participants were examined when “off” and “on” dopamine-replacement medication to determine the effects of medication on multi-segmental coordination when turning. The effect of walking velocity on the multi-segmental coordination of turning also was examined in healthy elderly participants for three different walking velocities. This research revealed differences in coordination patterns for standing versus walking turns and for healthy older adults versus persons with PD. Healthy older adults reorient their head, shoulder, and pelvis in unison, followed by mediolateral foot displacement, during standing turns. This coordination pattern was observed for both small and large turns. By contrast, turns initiated by healthy older adults while walking displayed a top-down temporal sequence similar to that reported for healthy young adults, i.e., the head turns first, followed by the shoulder and pelvis, and finally mediolateral displacement of the foot. This is a robust behavior which was not affected by the magnitude of the turn or walking velocity. PD participants (“off” and “on” medication) displayed temporal coordination patterns similar to age-matched healthy older adults for both standing and walking turns. However, PD participants (“off” and “on” medication) differed from healthy older adults with respect to the velocity and magnitude of reorientation of body segments, i.e., spatial parameters of coordination. The peak angular velocity of each body segment was significantly smaller for PD participants than the healthy older adults during both standing and walking turns; this was observed for both small and large magnitude turns. The magnitude of reorientation of each body segment was measured at the onset of mediolateral foot displacement; this measure revealed significantly smaller head and shoulder rotations for PD participants versus healthy older adults during standing turns, but not walking turns. Medication had no significant effect on the temporal or spatial parameters of body segment coordination during standing and walking turns. Medication increased the magnitude of head turn during the 90° standing turns; however, the magnitude of head turn remained smaller than that of healthy older adults. Multi-segmental coordination patterns differ for turns performed when standing (on-the-spot turn) versus when walking. The temporal parameters of these coordination patterns are not influenced by the magnitude of the turn or the velocity of walking and remain intact in Parkinson’s disease. Parkinson’s disease modifies the spatial parameters of coordination; reducing the velocity and early magnitude of reorientation of each body segment. These spatial parameters are not affected by dopaminergic medication.

It is difficult to think of any activity that does not require some degree of turning. Despite the prevalence of turning in daily activities and the challenge it poses to mobility-impaired individuals such as those with Parkinson’s disease, there is far less known about the multi-segmental control of turning than the control of standing and straight walking especially in elderly individuals and patient populations. The purpose of this thesis was to examine the coordination of body segment reorientation in healthy older adults and people with Parkinson’s disease (PD) during on-the-spot turns when standing and turns initiated when walking. The coordination of body segments was examined for small and large magnitude turns in both populations. PD participants were examined when “off” and “on” dopamine-replacement medication to determine the effects of medication on multi-segmental coordination when turning. The effect of walking velocity on the multi-segmental coordination of turning also was examined in healthy elderly participants for three different walking velocities. This research revealed differences in coordination patterns for standing versus walking turns and for healthy older adults versus persons with PD. Healthy older adults reorient their head, shoulder, and pelvis in unison, followed by mediolateral foot displacement, during standing turns. This coordination pattern was observed for both small and large turns. By contrast, turns initiated by healthy older adults while walking displayed a top-down temporal sequence similar to that reported for healthy young adults, i.e., the head turns first, followed by the shoulder and pelvis, and finally mediolateral displacement of the foot. This is a robust behavior which was not affected by the magnitude of the turn or walking velocity. PD participants (“off” and “on” medication) displayed temporal coordination patterns similar to age-matched healthy older adults for both standing and walking turns. However, PD participants (“off” and “on” medication) differed from healthy older adults with respect to the velocity and magnitude of reorientation of body segments, i.e., spatial parameters of coordination. The peak angular velocity of each body segment was significantly smaller for PD participants than the healthy older adults during both standing and walking turns; this was observed for both small and large magnitude turns. The magnitude of reorientation of each body segment was measured at the onset of mediolateral foot displacement; this measure revealed significantly smaller head and shoulder rotations for PD participants versus healthy older adults during standing turns, but not walking turns. Medication had no significant effect on the temporal or spatial parameters of body segment coordination during standing and walking turns. Medication increased the magnitude of head turn during the 90° standing turns; however, the magnitude of head turn remained smaller than that of healthy older adults. Multi-segmental coordination patterns differ for turns performed when standing (on-the-spot turn) versus when walking. The temporal parameters of these coordination patterns are not influenced by the magnitude of the turn or the velocity of walking and remain intact in Parkinson’s disease. Parkinson’s disease modifies the spatial parameters of coordination; reducing the velocity and early magnitude of reorientation of each body segment. These spatial parameters are not affected by dopaminergic medication.