Maximal calf circumference reflects calf muscle mass measured using magnetic resonance imaging

Background: Calf circumference (CC) has been used as a surrogate for calf muscle mass, which facilitates venous blood return to the heart through active skeletal muscle. However, the correlation between CC and calf muscle mass has not been extensively examined. This study aimed to examine the relationship between CC and calf muscle mass considering differences in sex and physique in elderly individuals. Methods: A total of 124 community-dwelling elderly individuals >= 60 years of age (61 men, mean [ +/- SD] age 74.3 +/- 5.7 years) were enrolled. Maximal CC was measured using a tape measure with the subject supine. The cross-sectional area of skeletal muscle tissues was measured using magnetic resonance imaging from the point of greatest calf circumference to 5 cm proximal and distal. Calf muscle mass was calculated by multiplying the area of each slice by slice thickness (5 mm). Results: CC was strongly correlated with calf muscle mass in male and female subjects (male: r = 0.908, P < 0.001; female: r = 0.892, P < 0.001). Multiple regression analysis revealed that CC and body mass index (BMI) were independent associate factors of calf muscle mass. The following estimation formulae were derived: (male) calf muscle mass (cm(3)) = 47.82 x CC (cm) - 12.50 x BMI (kg/m(2)) - 732.80; (female) calf muscle mass (cm(3)) = 32.23 x CC (cm) -4.85 x BMI (kg/m(2)) - 429.94. Conclusions: A strong correlation was found between CC and calf muscle mass according to magnetic resonance imaging. Sex differences and BMI should be considered for accurate estimation of calf muscle mass using CC.