Presumed reflex responses of human first dorsal interosseus muscle to naturally occurring twitch contractions of physiological tremor.
Surface EMG activity from the first dorsal interosseus, time-locked to twitch contractions in the same muscle, was investigated using the technique of spike-triggered averaging. A decrease in surface EMG activity was observed during the rising phase of twitch force, consistently followed by two bursts of activity with roughly constant onset latencies. One burst occurred at 45 msec from the onset of the single motor unit potential used to trigger the averager and was near the peak of the twitch contraction. The other burst occurred at 77 msec during the falling phase of the twitch contraction. If it is assumed that the chance synchronization of motor units contributes to physiological tremor [1, 5, 20], then the observed relative strengths of the two bursts of EMG activity indicate that their net action could enhance tremor.
D004558:Electric Stimulation; D004576:Electromyography; D006225:Hand; D006801:Humans; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction; D009132:Muscles / Q000294:innervation*; D011999:Recruitment, Neurophysiological; D012018:Reflex / Q000502:physiology*