Vibrations and sounds from evoked muscle twitches.

Muscle sounds are related to force production, fatigue, and pathology of muscle. However, sound data are frequently contaminated by tremor and motivational artifacts. Also, sound data are frequently reported in transducer-dependent units such as millivolts. To eliminate tremor and motivational artifacts and to obtain data in fundamental, nontransducer-dependent units, an accelerometer was used to record vibrations from human hand muscle twitches evoked by percutaneous stimulation. Reliable and reproducible waveforms were obtained from normal adult volunteers by recording from abductor pollicis brevis (APB) or abductor digiti quinti hand (ADQH) muscle after median or ulnar nerve stimulation, respectively. Latencies from the stimulus to the onset of the acceleration waveform were 5.7 +/- 0.6 and 5.1 +/- 0.6 ms, peak-to-peak amplitudes were 6.5 +/- 2.4 and 7.2 +/- 2.0 m/s2 for the APB and ADQH muscles, respectively.