Impact of Voluntary Muscle Activation on Stretch Reflex Excitability in Individuals With Hemiparetic Stroke.

Objective: To characterize how, following a stretch-induced attenuation, volitional muscle activation impacts stretch reflex activity in individuals with stroke.

Methods: A robotic device rotated the paretic elbow of individuals with hemiparetic stroke from 70° to 150°, and then back to 70° elbow flexion at an angular speed of 120°/s. This stretching sequence was repeated 20 times.

Experimentally Modifiable Parameters and Their Relation to the Tonic Vibration Reflex in Chronic Hemiparetic Stroke.

The tonic vibration reflex (TVR), a reflexive muscle contraction resulting from muscle or tendon vibration, is a useful tool in assessing spinal motoneuron excitability, particularly in hyperexcitable conditions, such as in chronic hemiparetic stroke. The influence of experimental parameters, for example the type of vibratory stimulus and limb configuration, and their interactions on the TVR response in chronic stroke is unknown, yet this knowledge is crucial for designing experiments with reliable TVR responses. Therefore, we conducted a screening experiment of six potential driving factors affecting the TVR response, with a D-optimal split plot fractional design matrix consisting of thirty-two combinations for each of the four participants with chronic hemiparetic stroke.

Limb position drift results from misalignment of proprioceptive and visual maps.

Previous work (Brown et al., 2003a,b) has shown that limb position drifts when individuals make repetitive movements in the absence of visual feedback. The purpose of this study was to examine whether limb position drift might reflect a misalignment in visual and proprioceptive maps by examining the nature of information used to specify new movements from a drifted limb position.