Faculty Advisor

Matt S. Stock, Ph.D.

Publication Date

Spring 2020

Abstract

Fast gait speed is being increasingly recognized as an important clinical tool in older adults. However, the underlying muscular and functional contributors to fast gait speed performance remain poorly understood.

PURPOSE: We sought to determine predictors of fast gait speed in older adults. We hypothesized that lower-extremity skeletal muscle size and quality would be strong predictors.

METHODS: Ninety community-dwelling older adults (33 men, 57 women; mean ± SD age = 74 ± 6 years) participated. B-mode ultrasonography was used to capture images of the vastus lateralis, rectus femoris, and gastrocnemius in the transverse plane. Each participant performed 30-second chair stand, heel-rise, functional reach, and grip strength tests. Fast gait speed was measured using the NIH Toolbox 4-Meter Walk Test. ImageJ software was used to quantify cross-sectional area (CSA), subcutaneous adipose tissue thickness, and echo intensity. Stepwise regression evaluated two prediction models, one using muscle morphology variables as independent variables, and another using muscle morphology variables and functional outcomes.

RESULTS: Most of the ultrasound variables exhibited weak-to-moderate correlations with fast gait speed (|r| range = 0.168 - 0.416). Model 1 indicated that the combination of medial gastrocnemius CSA and adipose tissue thickness explained 22.8% of the variance in fast gait speed. In Model 2, 30-second chair stand, heel-rise, and grip strength performance explained 45.5% of the variance.

CONCLUSION: While medial gastrocnemius morphology is important, measures of upper and lower-extremity muscle function are better predictors of fast gait speed. These results highlight a dissociation between skeletal muscle morphology and fast gait speed.

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