COMPARISON OF LABORATORY- AND FIELD-BASED ESTIMATES OF MUSCLE QUALITY FOR PREDICTING PHYSICAL FUNCTION IN OLDER WOMEN
C.R. Straight, A.O. Brady, M.D. Schmidt, E.M. Evans
J Aging Res Clin Practice 2013;2(3):276-279
Background: Muscle quality is related to physical function in older adults, however no study has investigated the utility of a field-based estimate for use in clinical settings. Objectives: This study investigated laboratory- and field-based measurements of muscle quality for predicting physical function in community-dwelling older women. Design: Cross-sectional. Setting: University research laboratory. Participants: Community-dwelling older women (n = 97, 73.9 ± 5.6 y). Measurements: Leg extension power using the Nottingham power rig, handgrip strength, body composition via dual-energy X-ray absorptiometry, and physical function (6-minute walk, 8-foot up-and-go, 30-second chair stand). Laboratory-based muscle quality (MQ-LAB) was defined as leg power (watts) normalized for lower-body mineral-free lean mass (kg) and field-based muscle quality (MQ-FIELD) was measured as handgrip strength normalized for body mass index. Results: MQ-LAB (r range = 0.42 to -0.63, all p < 0.01) and MQ-FIELD (r range = 0.37 to -0.50, all p < 0.01) had similar associations with measures of physical function. Using linear regression analysis, the percent improvement in physical function that could be expected from a 10% increase in muscle quality was similar for laboratory- and field-based estimates (2.7-4.4% vs. 2.6-3.8%, respectively). Conclusions: A field-based estimate of muscle quality provides a similar prediction of physical function to a laboratory-based approach in community-dwelling older women, and may be feasible for use in a clinical setting by practitioners.