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ABSTRACT:Objective: Many of the falls among people with Parkinson's disease (PD) occur during sudden, on-the-spot turning which requires systematic reorientation of axial segments towards the new direction. We examined whether a disturbance in the coordination of segmental reorientation is an important cause of turning difficulty in individuals with PD and is altered by dopaminergic medication. Methods: the sequence and timing of segmental reorientation during 45° and 90° on-the-spot turns was examined in fourteen individuals with PD while "off" and "on" medication and nineteen healthy controls (HC). Results: Regardless of the magnitude of the turn, HC reoriented their head, shoulder, and pelvis simultaneously followed by mediolateral foot displacement. PD patients displayed temporal coordination patterns similar to the HC. PD however, reduced the velocity and early magnitude of reorientation of each body segment which were both slightly improved by dopaminergic medication. Conclusion: Our finding that the HC and PD patients turn en bloc when the turn is predictable and there are no time constraints shows that the strategy of en bloc turning is not wrong if the movement parameters are unconstrained. However, in real life situations, which usually require quick and unpredictable turns, the en bloc strategy may be unsafe and more likely to result in falls. While in such situations HC are able to change the strategy from en bloc to sequential segmental turning, PD patients may not be able to do so and continue to turn en bloc. RÉSUMÉ: Maladie de Parkinson et coordination segmentaire au cours des changements de direction : I. les changements de direction sur place.Objectif : Plusieurs chutes chez les parkinsoniens surviennent pendant un changement de direction subit, sur place, qui requiert une réorientation systématique des segments axiaux vers une nouvelle direction. nous avons examiné si une perturbation de la coordination de la réorientation segmentaire est une cause importante des difficultés éprouvées par les parkinsoniens quand ils changent de direction et si la médication dopaminergique les modifient. Méthode : La séquence et la chronologie de la réorientation segmentaire au cours de changements de direction sur place à 45° et à 90°o nt été examinées chez 14 parkinsoniens sous médication en phase « off » et en phase « on » et chez 19 sujets témoins en bonne santé. Résultats : Quelle que soit l'ampleur du changement de direction, les sujets témoins réorientaient leur tête, leurs épaules et leur bassin simultanément et ceci était suivi d'un déplacement médio-latéral des pieds. Chez les parkinsoniens, la séquence temporelle de la coordination était semblable à celle des témoins. Cependant, au début du mouvement, la vitesse et l'ampleur de la réorientation de chaque segment corporel étaient diminuées chez les parkinsoniens. Ceci était amélioré légèrement par la médication dopaminergique. Conclusion : notre observation que les sujets témoins et les parkinsoniens tournent en bloc quand le changement de direction e...

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Objective: individuals with Parkinson's disease (PD) show poorer balance and greater incidence of falls while turning. We investigated whether a disturbance in timing and sequence of reorientation of body segments is a potential cause of turning difficulty in PD and is altered by levodopa. Methods: The sequence and timing of segmental reorientation during 45° and 90° walking turns were recorded in nineteen healthy controls and fourteen individuals with PD "off" and "on" medication. Results: both healthy elderly and PD patients "off" medication displayed a top-down sequence of segment reorientation, but differed with respect to the delay time between segments: PD "off" medication displayed a shorter delay between the onset of head and shoulder reorientation and longer delays for pelvis and foot reorientation. Furthermore, for all segments the peak angular velocities were lower for PD patients than healthy controls, with greater difference between the two groups during larger turns. While for both groups the velocity and magnitude of rotation of all segments were greater during larger turns, the relative timing of reorientation of segments remained the same during small and large turns. Medication had no significant effect on the timing and sequence of reorientation of segments and caused only a small and non-significant increase to segment velocities. Conclusion: This study further characterized the turning performance of individuals with PD. Our findings have clinical applications and therapeutic value for PD patients with difficulty turning. Understanding the specific deficiencies of turning performance of PD patients allows the therapists to opt for the most effective rehabilitation techniques. RÉSUMÉ: Maladie de Parkinson et coordination segmentaire au cours des changements de direction : I. les changements de direction sur place.Objectif : Plusieurs chutes chez les parkinsoniens surviennent pendant un changement de direction subit, sur place, qui requiert une réorientation systématique des segments axiaux vers une nouvelle direction. nous avons examiné si une perturbation de la coordination de la réorientation segmentaire est une cause importante des difficultés éprouvées par les parkinsoniens quand ils changent de direction et si la médication dopaminergique les modifient. Méthode : La séquence et la chronologie de la réorientation segmentaire au cours de changements de direction sur place à 45° et à 90°o nt été examinées chez 14 parkinsoniens sous médication en phase « off » et en phase « on » et chez 19 sujets témoins en bonne santé. Résultats : Quelle que soit l'ampleur du changement de direction, les sujets témoins réorientaient leur tête, leurs épaules et leur bassin simultanément et ceci était suivi d'un déplacement médio-latéral des pieds. Chez les parkinsoniens, la séquence temporelle de la coordination était semblable à celle des témoins. Cependant, au début du mouvement, la vitesse et l'ampleur de la réorientation de chaque segment corporel étaient diminuées chez les parkinsoniens. Ceci ...

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There are 3 significant challenges to sit-to-stand: (a) bringing the center of mass forward, (b) vertically raising the center of mass from the sitting to standing position, and (c) transition from a relatively large and stable base of support in sitting to a considerably smaller base of support when standing. The authors explored the challenges to stability control following sit-to-stand when the requirement for horizontal movement of the center of mass was influenced by foot position and their potential effect on the preceding phases of sit-to-stand. Eleven healthy young and 11 healthy elderly individuals performed the sit-to-stand with their feet further away and closer to the chair. Kinetic and kinematic data were recorded. Regardless of foot position, challenges in stability were greater in elderly participants than young participants despite their similar movement time and shear forces. The greater instability in elderly participants, despite their comparable movement characteristics, emphasizes the importance of stability control following sit-to-stand performance. For both young and elderly participants, the sit-to-stand duration and the shear forces were greater in the far condition. However, foot position did not affect the stability measures (i.e., duration of the stabilization phase and the total center of pressure path during the 1st second of the stabilization phase).

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