Muscle Quality Is Strongly Associated With Physical Function In Middle-aged And Older Adults

Abstract

There is an association between age related declines in muscle strength and muscle mass. This combination may result in loss of function and consequently increases in impairment and disability. Loss of function, increased impairment and disability results in higher rates of falls, chronic diseases, dependency, institutionalization, and mortality. Thus, the need to quantify and identify the underlying mechanisms that contribute to impairment and disability may provide insight to appropriate interventions and public health knowledge. PURPOSE: Explore the association in lower-limb muscle quality and physical function in a cross-sectional study of 93 adults (66.5±14.32 yrs.) METHODS: One repetition maximum (1RM) strength and peak power were determined using the pneumatic bilateral leg press. Physical function was assessed by a ten chair stand (10CH), 400M walk (400M), stair climb (STCL), and Short Physical Performance Battery (SPPB). Computed tomography was used to assess mid-thigh body composition. Muscle Quality was calculated from absolute strength and power results and adjusted for total muscle CSA to yield estimates of specific strength (SS) (N/cm2) and specific peak power (SP) (W/cm2) at 40% and 70% of the 1RM. RESULTS: There were high correlations for muscle quality and 1RM, 40%, and 70% of 1RM in all measures of function. The strongest correlations were 10CH and 40% and 70% SP (-0.494 and -0.517); 400M and 40% SP (-0.310); STCL and 40% and 70% SP (-0.503 and -0.542); SPPB and 40% and 70% SP (-0.587 and -0.594). Controlling for gender did not affect these relationships. CONCLUSION: Muscle quality is strongly associated with physical function. Normalizing force or power to cross-sectional thigh muscle area may be a better index of physical function than absolute maximal force production or thigh muscle area alone. Supported by the U.S. Department of Agriculture, under agreement No. 58-1950-7-707 and NIA AG-1884.