Erfassung des muskelfunktionszustandes durch bestimmung der muskelfaserleitgeschwindigkeit

In 20 healthy subjects (10 males and 10 females) aged between 24 and 45 years, the conduction velocity of excitation along muscle fibers (CV) was measured in biceps brachii muscle using level averaging of interference EMG recorded by branched and monopolar surface electrodes. The CV in children was investigated in 90 healthy infants aged up to 5 years. 43 newborns with brachial plexus palsy (BPP) (moderate and severe) was investigated, too. The measured CV, recorded with both monopolar and branched electrodes were significant equal (p > 0.05) at all different muscle tension (10, 25, 50 and 75% of MVC) and for all investigated healthy subjects. The CV was significant higher (p < 0.05) at 50 and 75% compared to 10 and 25% of MVC. In branched averaged potentials (AvPs) the terminal positive phase was suppressed. The monopolar AvPs were with waveform similar to those of motor units potentials and the parameters of the different potential's phases (including the terminal positive one) may give additional information for functional state of muscles. CV of healthy infants increased gradually with their age (from 1.56 ± 0.22 m/s to 3.26 ± 0.30 m/s). The value of CV depended significantly on the age. In newborns BPP the CV was higher in paretic arm and remains significantly higher (sever BPP) during the recovering period of one year. These findings may be explained with recovering predominantly of fast and large MUs, which have a higher CV. In conclusion, the level-triggered averaging of the interference EMG recorded from the skin surface by branched electrodes is an adequate noninvasive method for the measurement of the propagation velocity of excitation along the muscle fibers and for evaluation of changed muscle functional state.