Two types of sensorimotor strategies for whole-body movement in individuals with stroke: a pilot study.

PURPOSE: This study compared the sensory-motor interactions and strategies for whole-body movement in individuals with stroke who had damaged motor system area or sensory system area in the brain. METHODS: Participants with hemiparesis were asked to perform sit-to-stand movements while their vision was restricted, which can affect completion of the task. The participants were divided into two groups. The first group had no history of lesions in the sensory system area but did have a history of lesions in the motor system area (no damaged sensory-system: NDS). The second group had a history of lesions in the sensory system area of the brain (damaged sensory-system: DS). Center-of-pressure (COP) trajectories were measured to evaluate balance control in participants with and without vision, and numbers of sub-movements (i.e. numbers of segmented movements which reflect the degree of use of the feedback loops) were measured to evaluate feedforward and feedback control. Movement times were also measured. RESULTS: When vision was restricted, NDS participants showed increased variability in mediolateral COP trajectories during movement and utilized mainly feedforward control. In contrast, DS participants showed reduced variability in mediolateral COP trajectories during movement and utilized additional feedback control. CONCLUSIONS: These results demonstrate two types of strategies for whole-body movements in individuals with stroke. These differences may be attributed to whether the individual can compensate for vision with somatic senses and whether appropriate processing of somatosensory information has been lost. Individuals with hemiparesis created dexterous and flexible strategies to execute tasks successfully, depending on the characteristics of their sensorimotor disorders.

Sensorimotor Strategies in Individuals With Poststroke Hemiparesis When Standing Up Without Vision.

This study investigated the sensorimotor strategies for dynamic balance control in individuals with stroke by restricting sensory input that might influence task accomplishment. Sit-to-stand movements were performed with restricted vision by participants with hemiparesis and healthy controls. The authors evaluated the variability in the position of participants' center of mass and velocity, and the center-of-pressure position, in each orthogonal direction at the lift-off point. When vision was restricted, the variability in the mediolateral center-of-pressure position decreased significantly in individuals with hemiparesis, but not in healthy controls. Participants with hemiparesis adopted strategies that explicitly differed from those used by healthy individuals. Variability may be decreased in the direction that most requires accuracy. Individuals with hemiparesis have been reported to have asymmetrical balance deficits, and that meant they had to prioritize mediolateral motion control to prevent falling. This study suggests that individuals with hemiparesis adopt strategies appropriate to their characteristics.

Influence of constrained visual and somatic senses on controlling centre of mass during sit-to-stand.

This study aimed to investigate the manner in which healthy individuals execute robust whole body movements despite unstable body structure from the perspective of perception-action coupling. Twelve healthy adults performed sit-to-stand (STS) movements under conditions of constrained visual and somatic senses. During this movement, centre of mass (COM) of the body in the anterior-posterior, upward-downward and right-left directions was computed. The conditions of perceptual constraint were set as vision-restricted, somatosensory-restricted, vision- and somatosensory-restricted, and normal conditions. To evaluate COM control under these perceptual constraints, the variability in position and velocity of COM were assessed. The variabilities in COM velocity in the anterior-posterior and upward-downward directions decreased around the lift-off period only when both vision and somatic senses were constrained, whereas the variability of the COM position in the right-left direction increased under the somatosensory-restricted condition. Our findings suggested that control of COM velocity was enhanced in the major moving directions (anterior and upward directions) around the lift-off period during STS when both modalities of perception with regard to postural orientation were constrained. These motor regulations with perceptual constraints facilitate better adaptation to changes in body and environmental situations in daily life.

The contribution of quasi-joint stiffness of the ankle joint to gait in patients with hemiparesis.

BACKGROUND: The role of ankle joint stiffness during gait in patients with hemiparesis has not been clarified. The purpose of this study was to determine the contribution of quasi-joint stiffness of the ankle joint to spatiotemporal and kinetic parameters regarding gait in patients with hemiparesis due to brain tumor or stroke and healthy individuals. METHODS: Spatiotemporal and kinetic parameters regarding gait in twelve patients with hemiparesis due to brain tumor or stroke and nine healthy individuals were measured with a 3-dimensional motion analysis system. Quasi-joint stiffness was calculated from the slope of the linear regression of the moment-angle curve of the ankle joint during the second rocker. FINDINGS: There was no significant difference in quasi-joint stiffness among both sides of patients and the right side of controls. Quasi-joint stiffness on the paretic side of patients with hemiparesis positively correlated with maximal ankle power (r=0.73, P<0.01) and gait speed (r=0.66, P<0.05). In contrast, quasi-joint stiffness in controls negatively correlated with maximal ankle power (r=-0.73, P<0.05) and gait speed (r=-0.76, P<0.05). INTERPRETATION: Our findings suggested that ankle power during gait might be generated by increasing quasi-joint stiffness in patients with hemiparesis. In contrast, healthy individuals might decrease quasi-joint stiffness to avoid deceleration of forward tilt of the tibia. Our findings might be useful for selecting treatment for increased ankle stiffness due to contracture and spasticity in patients with hemiparesis.