Fig. 3
![Fig. 3](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40101-021-00270-0/MediaObjects/40101_2021_270_Fig2_HTML.png)
Simple linear regression for estimating quadriceps skeletal muscle volume (SMV) measured using magnetic resonance imaging (MRI). Simple linear regression relationship between quadriceps SMV using 50-kHz bioimpedance index (BI) (A), intracellular water index (ICW) (B), and muscle thickness index (C). A y = 36.1 × 50 kHz BI index + 545.7; R2 = 0.433; SEE = 198.5 cm3, 10.8%. B y = 78.4 × ICW index + 779.5; R2 = 0.551; SEE = 176.6 cm3, 9.6%. C y = 10.3 × muscle thickness index + 35.3; R2 = 0.543; SEE = 178.1 cm3, 9.7%