Dynamic electrical characteristics of the muscle with the fatigue during exercise

Abstract

Although there is an invasive method, the procedure to quantitate the muscle fatigue today is not fully established. This study analyzes the muscle fatigue by measuring cross electric property of the muscle with working load noninvasively. We measured the electrical impedance of the muscle to obtain the relationship between the electrical property and the fatigue during exercise. Several Ag/AgCl electrodes are placed the biceps brachii muscle crossing the arm. The baseline drift due to the sweat glands on the skin was effectively eliminated by subtracting one of the exercised arm from one of the resting arm, and the interelectrode impedance was measured. The fatigue of the arm was loaded by flexing exercise with a 2 kg iron array. The rate of flexing was once per second. The impedance was acquired every 30 seconds. The flexing was constant but ceased while acquiring the impedance value for 5 seconds. As a result impedance increased at the beginning, and then decreased after 90 seconds, or started decreasing after the beginning of the exercise. These phenomena were well reproducible. The initial increase of the impedance was concluded as with the fatigue which may triggered the increase of the lactic acid in the muscle. The decrease of the impedance in the latter part was probably due to the influence of increased blood flow, which was simultaneously measured in this study.