Altered trunk position sense and its relation to balance functions in people post-stroke.

Objective: To determine whether trunk position sense is impaired in people with poststroke hemiparesis.

Background: Good trunk stability is essential for balance and extremity use during daily functional activities and higher level tasks. Dynamic stability of the trunk requires adequate flexibility, muscle strength, neural control, and proprioception.

Strength and coordination in the paretic leg of individuals following acute stroke.

The goal of this study was to determine whether acute stroke survivors demonstrate abnormal synergy patterns in their affected lower extremity. During maximum isometric contractions with subjects in a standing position, joint torques generated simultaneously at the knee and hip were measured, along with associated muscle activation patterns in eight lower limb muscles. Ten acute stroke survivors and nine age-match controls participated in the study.

Greater reliance on impedance control in the nondominant arm compared with the dominant arm when adapting to a novel dynamic environment.

This study investigated differences in adaptation to a novel dynamic environment between the dominant and nondominant arms in 16 naive, right-handed, neurologically intact subjects. Subjects held onto the handle of a robotic manipulandum and executed reaching movements within a horizontal plane following a pseudo-random sequence of targets. Curl field perturbations were imposed by the robot motors, and we compared the rate and quality of adaptation between dominant and nondominant arms.

Quantification of the dynamic properties of EMG patterns during gait.

A technique for analyzing and comparing the dynamic properties of electromyographic (EMG) patterns collected during gait is presented. A gait metric is computed, consisting of both magnitude (amplitude) and phase (timing) components. For the magnitude component, the processed EMG pattern is compared to a normative EMG pattern obtained under similar walking conditions, where the metric is incremented if the muscle is firing during expected active regions or is silent during expected inactive regions.

Alterations in muscle activation patterns during robotic-assisted walking.

Objective: The goal of this study was to compare the muscle activation patterns in various major leg muscles during treadmill ambulation with those exhibited during robotic-assisted walking.

Background: Robotic devices are now being integrated into neurorehabilitation programs with promising results. The influence of these devices on altering naturally occurring muscle activation patterns utilized during walking have not been quantified.

Evidence for force-feedback inhibition in chronic stroke.

The presence of force-feedback inhibition was explored during reflex responses in five subjects with known incidence of stroke. Using constant velocity stretches, it was previously found that after movement onset, active reflex force progressively increases with increasing joint angle, at a rate proportional to a fractional exponent of the speed of stretch. However, after the reflex force magnitude exceeds a particular level, it begins rolling off until maintaining a steady-state value.

Elbow impedance during goal-directed movements.

The mechanical properties and reflex actions of muscles crossing the elbow joint were examined during a 60-deg voluntary elbow extension movement. Brief unexpected torque pulses of identical magnitude and time-course (20-Nm extension switching to 20-Nm flexion within 30 ms) were introduced at various points of a movement in randomly selected trials. Single pulses were injected in different trials, some before movement onset and some either during early, mid, late or ending stages of the movement.

Frequency response characteristics of ankle plantar flexors in humans following spinal cord injury: relation to degree of spasticity.

Frequency response characteristics of the ankle plantar flexors were studied in adults both with and without spinal cord injury (SCI) to determine how the muscle contractile properties change after SCI. and to see if there is a relation between the severity of spasticity and how the properties change. Ten controls and ten complete, chronic spinal cord injured subjects were tested, where the tibial nerve was stimulated electrically in a stochastic manner with the ankle fixed isometrically at various joint angles.