Correcting for subcutaneous fat: Does it improve the correlation between vastus lateralis echo intensity and physical performance in older women?

Numerous studies have corrected the echo intensity of the vastus lateralis for subcutaneous fat thickness. However, it is unclear if correction for subcutaneous fat improves the correlation between vastus lateralis echo intensity and physical performance. We aimed to examine the correlations between vastus lateralis muscle morphology parameters and physical performance outcomes in older women. Twenty healthy older women (67 ± 4 years) participated in this study. Muscle cross-sectional area, raw and corrected echo intensity and subcutaneous fat thickness were determined from ultrasound scans of the vastus lateralis. Physical performance was assessed from timed up-and-go and 6 min walk tests. Raw echo intensity was significantly related to timed up-and-go scores (r = 0.552, p = 0.012) and 6 min walk distance (r = -0.462, p = 0.040), whereas corrected echo intensity was not significantly associated with these performances (r = 0.433, p = 0.056 and r = -0.373, p = 0.105). There was a nonsignificant correlation between raw echo intensity and subcutaneous fat thickness (r = 0.353, p = 0.126). There were also nonsignificant correlations between muscle cross-sectional area and timed up-and-go scores (r = -0.189, p = 0.426) and 6 min walk distance (r = 0.298, p = 0.201). The results of our study showed that raw echo intensity correlated better than corrected echo intensity with physical performance. These findings question the need to correct the echo intensity of the vastus lateralis for subcutaneous fat thickness in older adults.