Abnormal joint torque patterns in the paretic upper limb of subjects with hemiparesis. New York: Harper and Row (1970).ĭewald JP, Beer RF. Movement Therapy in Hemiplegia: A Neurophysiological Approach. Differences between flexion and extension synergy-driven coupling at the elbow, wrist, and fingers of individuals with chronic hemiparetic stroke. Asterisks indicate that synergy-driven torque for a given primary torque direction was significantly lower value than that for SABD ( p-values range from < 0.0001 to 0.02 exact values are reported in the text). This was calculated by averaging the magnitude of all secondary torques generated during the performance of a given primary torque direction. (B) The mean synergy-driven torque generated by each primary torque direction for the paretic limb. These findings are related to the WFTS device and positioning and are not believed to have scientific relevance. Normalized torques in wrist flexion and extension for the non-paretic and control data that are not near maximum resulted because maximal torque values often occurred during combined rather than the wrist and finger flexion or extension. Non-paretic and control data were similar with no meaningful variations. Asterisks indicate significant differences between paretic and non-paretic limbs ( p-values range from < 0.0001 to 0.01) from our planned comparisons on the limb-by-secondary torque interactions. For the paretic limb, red bars highlight SABD and flexion directions, and blue bars highlight SADD and extension directions for the paretic limb. (A) Group mean ± SEM shoulder, elbow, wrist, and finger joint torques produced by the paretic (red/blue), non-paretic (gray), and control (white) limbs during the generation of SABD, SADD, EF, EE, WF, WE, FF, and FE MVT. Results provide indirect evidence linking the influence of brainstem motor pathways to abnormal motor behaviors post-stroke, and they demonstrate the need to examine whole-limb behavior when studying or seeking to rehabilitate the paretic upper limb.Īssociated reaction brainstem motor pathways extension synergy flexion synergy rehabilitation stroke upper limb. Associated reactions in the wrist/finger flexors were stronger than those of other paretic muscles and were the only ones whose response depended on whether the non-paretic contraction was at a proximal or distal joint. Synergy-driven contractions were strongest when elicited via proximal joints and weakest when elicited via distal joints. For some participants, joint torque and muscle activation generated during maximal voluntary contractions were lower than during maximal synergy-induced contractions (i.e., contractions about a different joint), particularly for wrist and fingers.

Isometric joint torques and surface EMG were recorded from shoulder, elbow, wrist, and finger joints and muscles. Twelve participants with moderate-to-severe hemiparetic stroke and six without stroke performed maximal isometric torque generation in eight directions: shoulder abduction/adduction and elbow, wrist, and finger flexion/extension. If upregulation of brainstem motor pathways occurs following stroke-induced corticofugal tract damage, then we would expect a pattern of muscle dependency in the observed behaviors consistent with such neural reorganization. Here we formally investigated these observations and interpreted them within the context of the neural mechanisms thought to underlie stereotypical movement patterns.

distal muscles and associated reactions in the paretic limb occurred during maximal efforts with the non-paretic limb, the strength of which seemed to vary depending on which muscles in the non-paretic limb were contracting. It seemed that: paretic wrist/finger muscles were activated maximally during contractions of muscles at a different joint differences in the magnitude of synergy expression occurred when elicited via contraction of proximal vs. During our recent work on differences in synergy expression among proximal and distal joints, we serendipitously observed some notable characteristics of synergy-driven muscle activation.

Accumulating evidence indicates that these synergies emerge because of upregulation of diffusely projecting brainstem motor pathways following stroke-induced damage to corticofugal pathways. Individuals with moderate-to-severe post-stroke hemiparesis cannot control proximal and distal joints of the arm independently because they are constrained to stereotypical movement patterns called flexion and extension synergies.

Flexion synergy pattern after stroke