Effects of age on muscle as measured by electrical impedance myography

Electrical impedance myography ( EIM) is a painless and non-invasive technique for the assessment of muscle which we apply here to the effects of normal aging. The paper presents a cross-sectional analysis of EIM data from the quadriceps and tibialis anterior of 100 healthy subjects ( 44 men, 56 women, ages 18 - 90 years). The principal EIM parameter, the spatially averaged phase theta(avg), shows a roughly quadratic reduction with increasing age, declining more steeply beyond 60 years. The correlation was stronger in men ( quadriceps: r(2) = 0.68 for men, 0.52 for women; tibialis anterior: r(2) = 0.74 for men, 0.38 for women; p < 0.001 throughout). Additionally, four subjects ( age greater than 75 years) were asked to return for repeat testing several years after their initial assessment. These longitudinal results qualitatively confirm the cross-sectional data, though with greater reductions in theta(avg) at high age. The findings of this study support the potential use of EIM as a simple and effort-independent test of muscle health in the elderly.