Local fat content and muscle quality measured by a new electrical impedance myography device: correlations with ultrasound variables

The present study investigated the relationship between local fat percentage (SKfat) and muscle quality (MQ) estimated by a new hand-held electrical impedance myography (hEIM) device or derived from ultrasound and strength assessments. The right anterior thigh of 90 healthy participants (mean±SD; age=22.9±2.9 years; 46 men: BMI=23.9 ± 2.4 kgm-2; 46 women: BMI=21.1 ± 1.9 kgm-2) was scanned by hEIM and ultrasound. Correlations between SKfat, local subcutaneous fat (SUBfat), and echo intensity (EIus) were explored. Correlations between MQ, EIus, quadriceps femoris anatomical cross-sectional area (ACSAQF), knee extensors maximum voluntary isometric torque (T), T/ACSAQF, EIus/SUBfat, and ACSAQF/SUBfat were also assessed. SKfat correlated with SUBfat (r=0.88; p<0.001) and EIus (r=0.64; p<0.001). MQ correlated with EIus (r=-0.66; p<0.001), ACSAQF (r=0.37; p<0.001), EIus/SUBfat (r=0.37; p<0.001), and ACSAQF/SUBfat (r=0.81; p<0.001). Multiple regression analysis showed that SUBfat, EIus, and sex explained 86% of SKfat variance, whereas ACSAQF/SUBfat, sex and EIus explained 75% of MQ variance. In conclusion, high hEIM local fat percentage relates to greater subcutaneous fat and intramuscular non-contractile tissue content. High hEIM muscle quality relates to greater muscle-size:subcutaneous-fat ratio and contractile tissue content. Sex influences the prediction of both parameters. This hEIM device seems to be useful to estimate local thigh composition.