Potential Utility of Electrical Impedance Myography in Evaluating Age-Related Skeletal Muscle Function Deficits

Abstract

Skeletal muscle function deficits associated with advancing age are due to several physiological and morphological changes including loss of muscle size and quality (conceptualized as a reduction in the intrinsic force-generating capacity of a muscle when adjusted for muscle size). Several factors can contribute to loss of muscle quality, including denervation, excitation-contraction uncoupling, increased fibrosis, and myosteatosis (excessive levels of inter- and intramuscular adipose tissue and intramyocellular lipids). These factors also adversely affect metabolic function. There is a major unmet need for tools to rapidly and easily assess muscle mass and quality in clinical settings with minimal patient and provider burden. Herein, we discuss the potential for electrical impedance myography (EIM) as a tool to evaluate muscle mass and quality in older adults. EIM applies weak, non-detectible (e.g., 400 μA), mutifrequency (e.g., 1 kHz–1 MHz) electrical currents to a muscle (or muscle group) through two excitation electrodes, and resulting voltages are measured via two sense electrodes. Measurements are fast (~5 s/muscle), simple to perform, and unaffected by factors such as hydration that may affect other simple measures of muscle status. After nearly 2 decades of study, EIM has been shown to reflect muscle health status, including the presence of atrophy, fibrosis, and fatty infiltration, in a variety of conditions (e.g., developmental growth and maturation, conditioning/deconditioning, and obesity) and neuromuscular diseases states [e.g., amyotrophic lateral sclerosis (ALS) and muscular dystrophies]. In this article, we describe prior work and current evidence of EIM’s potential utility as a measure of muscle health in aging and geriatric medicine.

Evaluation of Skeletal Muscle Dysfunction Associated With Acute Inflammation by Electrical Impedance Myography: A Case Report on Skeletal Muscle Dysfunction After Cardiac Surgery and Literature Review

“…To the best of our knowledge, this is the first report to evaluate EIM for inflammatory skeletal muscle dysfunction after surgery. Previous studies have shown that the impedance parameters measured by EIM are associated with age-related changes in skeletal muscle and neuromuscular diseases [ 2 ]. In this case, acute changes in skeletal muscle function caused by inflammatory reactions after thoracotomy were serially evaluated using ultrasonography and EIM to determine the efficacy of EIM.…”

“…EIM has been reported to be effective in aging and sarcopenia-induced changes in skeletal muscle function [ 2 ]. Because EIM is sensitive to minor morphological changes, such as cell density and size in tissues, it is useful not only for age-related changes but also for disease-genic changes [ 7 ].…”

“…Bioelectrical impedance technology has been used in the medical field to assess body composition, such as body water, skeletal muscle, and fat content [ 1 ]. Recently, a diagnostic technique called electrical impedance myography (EIM) has been proposed, which measures the intrinsic impedance of skeletal muscle using these techniques [ 2 ]. In EIM, a variety of numerical values are calculated, including the phase angle (PA) and the ratio of intracellular to extracellular fluid resistance ( R i / R e ), the beta parameter ( β ) that represents tissue uniformity, and the center frequency ( f c ).…”

“…In EIM, a variety of numerical values are calculated, including the phase angle (PA) and the ratio of intracellular to extracellular fluid resistance ( R i / R e ), the beta parameter ( β ) that represents tissue uniformity, and the center frequency ( f c ). These parameters have been shown to be related to muscle fiber mass and fascial function in skeletal muscles [ 2 ]. We investigated the effectiveness of skeletal muscle quality and quantitative assessment of the impedance parameters of the upper and lower limb measured by direct segmental multifrequency bioelectrical impedance analysis and found that R i /R e correlates with muscle mass and beta parameters with muscle mass indices and that each has an independent effect on muscle strength [ 3 ].…”

Interrater and Intrarater Reliability of Electrical Impedance Myography: A Comparison between Large and Small Handheld Electrode Arrays

“…There is gap in the literature in assessing if large or small sensors are sufficiently reliable for clinical application, or if their reliability may differ when measuring a single muscle group by different rates at different time. A recent review by Clark et al argued that there continues to be a lack of evidence to support the clinical application of EIM in assessing skeletal muscle function [ 22 ]. These issues must be addressed to facilitate clinical application of EIM.…”