Computed Tomography-Based Muscle Attenuation and Electrical Impedance Myography as Indicators of Trunk Muscle Strength Independent of Muscle Size in Older Adults

Abstract

Objective—To examine the associations of computed tomography (CT) -based x-ray attenuation and paraspinal electrical impedance myography (EIM) measures of trunk muscles with absolute and relative (normalized by body weight) trunk extension strength, independent of muscle cross- sectional area (CSA). Design—A cross-sectional study of mobility-limited community dwelling older adults (34 women, 15 men, mean age 78.2±7.2 years) recruited from within an existing prospective research cohort. Trunk extension strength, CT-based trunk muscle CSA and attenuation at L4 level, and paraspinal EIM measures were collected. Results—Attenuation was positively correlated with absolute and relative strength for multiple muscle groups (r = 0.32 to 0.61, p < 0.05). Paraspinal EIM phase was positively correlated with paraspinal attenuation (r = 0.30, p = 0.039) and with relative strength (r = 0.30, p = 0.042). In multivariable linear regressions adjusting for sex and CSA, attenuations of the anterior abdominal muscles (semipartial r2 = 0.11, p = 0.013) and combined muscles (semipartial r2 = 0.07, p = 0.046) were associated with relative strength. Conclusions—While attenuation was associated with relative strength, small effect sizes indicate limited usefulness as clinical measures of muscle strength independent of muscle size. However, there remains a need for additional studies in larger and more diverse groups of subjects.