Influence of body mass normalization on the correlations between muscle cross-sectional area and physical performance outcomes in older women.

Abstract

Normalization is a method used to account for body mass in clinical practice and research. It is unclear if thismethod will improve the correlation between muscle cross-sectional area (CSA) and physical performance. We examinedthe correlations between quadriceps muscle morphology parameters and physical performance outcomes in older women.Material and methods: Twenty older women participated in this study. Ultrasound imaging was used to measure quadricepsmuscle CSA and echo intensity. Muscle CSA was expressed as an absolute value (cm2) and as a relative value normalized tobody mass (cm2/kg). Physical performance was assessed from timed up-and-go and 6-min walk tests. Relative CSAwas significantly related to timed up-and-go scores (r=-0.489, p=0.029) and 6-min walking speed (r=0.606, p=0.005), whereasabsolute CSA was not significantly associated with these performances (r=-0.231, p=0.327 and r=0.373, p=0.105). There wasa significant correlation between absolute CSA and body mass (r=0.456, p=0.043). There were also significant correlationsbetween echo intensity and timed up-and-go scores (r=0.556, p=0.011) and 6-min walking speed (r=-0.484, p=0.031). Our study showed that relative CSA correlated better than absolute CSA with physical performance. These findingssupport the need to normalize measurements of muscle CSA to body mass in older adults.