In this study, we examined the associations among the intra-/inter-examiner reproducibility of anterior central femoral muscle thickness (muscle thickness), femoral circumference, and anterior femoral muscle hardness (muscle hardness) measurement and knee extension muscle strength. The subjects were 20 healthy adults (mean age; male 20.1 ±0.3 years, female 20.2±0.4 years, total: 40 bilateral lower limbs). The muscle thickness,femoral circumference, and muscle hardness were measured twice, respectively, and the interclass correlation coefficient was calculated to investigate the intra-/inter-examiner reproducibility. Furthermore, the correlation between the knee extension muscle strength and each item was examined by calculating Pearsonʼs correlation coefficient. The interclass correlation coefficients of the reproducibility of the muscle thickness, fat thickness, and femoral circumference were ?0.9 regardless of sex, but the inter-examiner correlation coefficients of the muscle hardness in males and females were 0.763 and 0.787, respectively. Only the femoral circumference in males was correlated with the muscle strength (r=0.54,p<0.05). These results suggest that the reproducibility of data should be considered for muscle hardness measurement, and that the influence of fat thickness on the femoral circumference in females must be considered, although the femoral circumference in males reflects the knee extension muscle strength.
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