[Objective] To develop a formula to estimate the skeletal muscle mass index (SMI) of young women using simple measurable items.
[Methods] The study included 117 female students (18.8 ± 0.8 years old) who signed the consent in advance and were able to undergo the following measurements: height, weight, body fat percentage, body fat mass, appendicular muscle mass, grip strength, and calf circumference. Height was measured with a stadiometer, whereas weight and composition were measured using bioelectrical impedance analysis. To generate a more precise SMI estimation formula, the calf circumference index (CCI) [body fat mass (kg)/(calf circumference [m])2 ]was invented, and multiple regression analysis was performed using variables selected by a stepwise method. SMIs were used as response variables and explanatory variables were selected from body mass index (BMI), body fat mass, grip strength, calf circumference, and CCI.
[Results] The mean SMI was 7.2 ± 0.6 kg. Although a significant correlation was observed in terms of all variables, CCI (p < 0.001) had the highest correlation coefficient. A highly precise SMI estimation formula based on BMI and CCI was developed using the following regression model formula (R2 = 0.89):
SMI = 3.003 + 0.297BMI -0.020CCI
[Conclusion] The SMI estimation formula developed herein can be calculated using a simple measurement method, facilitating self-evaluation of skeletal muscle mass. This information is expected to allow prevention of sarcopenia in young women at an early stage.
