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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.

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METHODS: 15 males (have at least 1 year of RT, 24.47±1.64 years, 180.4±4.82cm, weight were 82.27±10.83kg, 1RM were 154.73±23.32kg) volunteered to participate in this study. Subjects were asked to the laboratory for 5 separate visits. The 1RM was determined by two 1RM tests. In the next three sessions, respectively, subjects performed the squat with the Smith machine with the three intensities, including 40%1RM, 60%1RM, and 80%1RM. Each intensity consisted of 3 sets 5 repetitions and 4-min rest between sets. Oxygen uptake(VO2) was measured from 15 minutes before exercise to 60 minutes after exercise, continuously. The duration of EPOC was recorded until 2 subsequent measurements fell below 5.0 ml•kg-1•min-1. EPOC was converted to energy expenditure as 1L of O2=19.6 KJ. The data were statistically using ANOVA, and the significance level was set at P≤0. 05. RESULTS: a)The magnitude of EPOC with 40%1RM, 60%1RM, and 80%1RM squat were 61.40±12.72 KJ,90.54±16.80 KJ, 109.4±21.52 KJ, respectively. The magnitude of EPOC between 40%1RM,60%1RM, and 80%1RM was all had significantly different (P≤0. 05). b)The duration of EPOC with 40%1RM, 60%1RM and 80%1RM squat were 178.0±80.55s(90s,345s),239.0±86.81s(150s,480s), 332.0±274.7s(120s,1260s), respectively. The duration of EPOC of 60%1RM squat was significantly greater than 40%1RM(P=0.0159). There was no significant difference in other results. CONCLUSIONS: a) Under the condition of controlling the number of exercise groups and times, the magnitude of EPOC increased with the increase of exercise intensity b) the duration of EPOC of 40%1RM, 60%1RM and 80%1RM was less than 15 minutes after 3 sets 5 repetitions.

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The original version of this article unfortunately contained a mistake. The Figure 1 image and legend were published erroneously.The corrected Figure 1 and legend are shown in the next page.