Echo Intensity Reliability for the Analysis of Different Muscle Areas in Athletes

Lanferdini, FJ, Manganelli, BF, Lopez, P, Klein, KD, Cadore, EL, and Vaz, MA. Echo intensity reliability for the analysis of different muscle areas in athletes. J Strength Cond Res 33(12): 3353-3360, 2019-Skeletal muscles' echo intensity (EI) is used as a parameter to evaluate muscle damage and muscle quality after exercise or training. However, recent muscle EI studies have used regions of interest (ROIs) of different sizes for assessing muscle damage and muscle quality, which may lead to different results if the different ROIs from the same muscle are not reliable. Although a maximum rectangular ROI (RET-ROI), included in the muscles' anatomical cross-sectional area, can be used to represent the maximum muscle ROI (MAX-ROI), no studies were found that investigated the reliability of the evaluations of different ROIs for the EI of superficial vs. deep muscles of the thigh. In addition, no studies have evaluated different ROIs in cyclists, at different days and analyzed by different raters. The aim of this study was to evaluate the EI reliability of rectus femoris (RF) and vastus intermedius (VI) muscles of cyclists. Twenty cyclists visited the laboratory 4 times for the evaluation of RF and VI muscles transversal ultrasound images. Echo intensity was determined from grayscale mean values by 2 examiners who performed the analysis with 3 different ROIs: MAX-ROI, RET-ROI, and 1-cm ROI (1CM-ROI). The between-ROI EI data reliability showed a strong correlation in both RF (r ≥ 0.79) and VI (r ≥ 0.87) muscles. Bland-Altman tests demonstrated high agreement among RF ROI muscle areas (p > 0.05), with no agreement between the VI areas (p < 0.05). Only the RF muscle MAX-ROI, RET-ROI, and 1CM-ROI areas are similar for EI analysis, with no similarities for the same VI muscle areas.