Impedance Alterations in Healthy and Diseased Mice During Electrically Induced Muscle Contraction

Abstract

Abstract-Alterations in the health of muscles can be evaluated through the use of electrical impedance myography (EIM). To date, however, nearly all work in this field has relied upon the measurement of muscle at rest. To provide insight into the contractile mechanisms of healthy and disease muscle, we evaluated the alterations in the spectroscopic impedance behavior of muscle during the active process of muscle contraction. The gastrocnemii from a total of 13 mice were studied (5 wild type, 4 muscular dystrophy animals, and 4 amyotrophic lateral sclerosis animals). Muscle contraction was induced via monophasic current pulse stimulation of the sciatic nerve. Simultaneously, multisine EIM (1 kHz to 1 MHz) and force measurements of the muscle were performed. Stimulation was applied at 3 different rates to produce mild, moderate and strong contractions. We identified changes in both single and multifrequency data, as assessed by the Cole impedance model parameters. The processes of contraction and relaxation were clearly identified in the impedance spectra and quantified via derivative plots. Reductions in the center frequency f c were observed during the contraction consistent with increasing muscle fiber diameter. Different EIM stimulation rate-dependencies were also detected across the 3 groups of animals.

Guidelines to electrode positioning for human and animal electrical impedance myography research

“…The amplitude ratio and phase lag between the current and voltage signals defines the so-called “electrical impedance” at that particular frequency (typically in the kHz-MHz range)9101112. The practical relevance of EIM as a non-invasive and painless biomarker has been demonstrated extensively in the recent years in a variety of disorders, including spinal muscular atrophy1314, amyotrophic lateral sclerosis1516, and Duchenne muscular dystrophy1718.…”

Assessment OF aged mdx mice by electrical impedance myography and magnetic resonance imaging

“…As anticipated, mdx mice were significantly weaker and had more collagen content and smaller muscle fibers when compared with WT mice, in concordance with previous studies. 3,27 Both EIM parameters and T2 mapping had similarly strong correlations with these muscle strength and composition parameters, suggesting that all of these factors help explain the observed differences between WT and mdx animals.…”

Electrical Impedance Myography and Its Applications in Neuromuscular Disorders

“…In fact, current standard approaches such as needle EMG or nerve conduction studies only measure up to the point of muscle fiber depolarization, ignoring entirely the contractile process itself. Supporting this application, recent animal studies have shown impedance alterations in muscle contraction are diseasedependent [110]. Further development and application of impedance for the measurement of muscle contraction in real time could serve as a useful research tool with potential long-term clinical value.…”