PubMed · 15406965
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A LUNDERVOLD. 1949. A technical error in electromyography.. https://pubmed.ncbi.nlm.nih.gov/15406965/
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The purpose of this short review is to consider the various hypotheses that are attributed to genesis of physiological tremor seen in the human jaw during isometric contractions.
In this paper we present an optimal wavelet packet (OWP) method based on Davies-Bouldin criterion for the classification of surface electromyographic signals. To reduce the feature dimensionality of the outputs of the OWP decomposition, the principle components analysis was employed. Then we chose a neural network classifier to discriminate four types of prosthesis movements. The proposed method achieved a mean classification accuracy of 93.75%, which outperformed the method using the energy of wavelet packet coefficients (with mean classification accuracy 86.25%) and the fuzzy wavelet packet method (87.5%).
OBJECTIVE: To elucidate mechanisms of impaired force production in post-stroke hemiparesis. METHODS: Knee extensor torque-velocity and activation-velocity relationships were examined in seventeen persons with post-stroke hemiparesis (age 57.5, +/-6.9) and thirteen non-disabled (age 63.0 +/-10.4) persons. RESULTS: Velocity-dependent concentric torque impairment was exaggerated in subjects with hemiparesis relative to control subjects (p<.001). Muscle power was also less in the group with hemiparesis (p<.001), and plateaued at velocities > or =90deg/s (p>.05). In the control group agonist EMG during concentric actions exhibited a positive linear relationship as velocity increased (R(2)=.93, p<.05). The group with hemiparesis produced 34-60% less agonist EMG than controls (p<.02) and modulation was absent (p>.05). Antagonist EMG was either greater in the control (biceps femoris, p<.006) or similar between groups (semimembranosus, p=.95). Under eccentric testing conditions, torque normalized to peak isometric torque (p=.44) and rectus femoris activation (p=.33) were similar between groups, indicating a relative preservation of eccentric torque producing capacity post-stroke. CONCLUSIONS: Certain clinical perspectives assert that weakness following central nervous system injury stems from spastic antagonist restraint. Instead, absence of an antagonist restraint strongly suggests that impaired agonist activation is the principal determinant of hemiparetic weakness. SIGNIFICANCE: These findings have important implications for promoting optimal recovery of motor function in neuro-rehabilitation.