The variation of action potential and impedance in human skeletal muscle during voluntary contraction.
We used an insulated acupuncture needle to deliver a 20 kHz alternative current to detect the changes on the electromyogram (EMG) and deep muscle impedance. We found that impedance increased (with a duration of 224.1 +/- 75.3 msec) and then decreased (with a duration of 293.4 +/- 97.3 msec) after motor unit action potential (MUAP) firing during isometric voluntary contraction (VC) of the tibialis anterior muscle (TAM). We divided the positive peak into pattern I (with a latency range of > or = 30 msec and < or = 75 msec) and pattern II (with a latency range of > 75 msec and < or = 140 msec). These patterns of change corresponded to the contraction times of tension caused by the electrical stimulation and VC. These impedance changes may be caused by a change in the extracellular and intracellular fractions, and may reflect the variance of tension intensity in the muscle tissue.
Liao
T J
TJ
Department of Oriental Medicine, Meiji College of Oriental Medicine, Kyoto, Japan.
Nishikawa
H
H
D000200:Action Potentials; D000328:Adult; D017097:Electric Impedance; D004558:Electric Stimulation; D004576:Electromyography; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009132:Muscles / Q000502:physiology*; D014836:Volition