Validity of ultrasound muscle thickness measurements for predicting leg skeletal muscle mass in healthy Japanese middle-aged and older individuals.
BACKGROUND
The skeletal muscle mass of the lower limb plays a role in its mobility during daily life. From the perspective of physical resources, leg muscle mass dominantly decreases after the end of the fifth decade. Therefore, an accurate estimate of the muscle mass is important for the middle-aged and older population. The present study aimed to clarify the validity of ultrasound muscle thickness (MT) measurements for predicting leg skeletal muscle mass (SM) in the healthy Japanese middle-aged and older population.


RESULTS
MTs at four sites of the lower limb and the bone-free lean tissue mass (LTM) of the right leg were determined using brightness-mode ultrasonography and dual-energy X-ray absorptiometry (DXA), respectively, in 44 women and 33 men, 52- to 78-years old. LTM was used as a representative variable of leg skeletal muscle mass. In the model-development group (30 women and 22 men), regression analysis produced an equation with R2 and standard error of the estimate (SEE) of 0.958 and 0.3 kg, respectively: LTM (kg) = 0.01464 × (MTSUM×L) (cm2) - 2.767, where MTSUM is the sum of the product of MTs at four sites, and L is length of segment where MT is determined. The estimated LTM (7.0 ± 1.7 kg) did not significantly differ from the measured LTM (7.0 ± 1.7 kg), without a significant systematic error on a Bland-Altman plot. The application of this equation for the cross-validation group (14 women and 11 men) did not yield a significant difference between the measured (7.2 ± 1.6 kg) or estimated (7.2 ± 1.6 kg) LTM and systematic error.


CONCLUSIONS
The developed prediction equation may be useful for estimating the lean tissue mass of the lower extremity for the healthy Japanese middle-aged and older population.
National Institute of Fitness and Sports in Kanoya, 1 Shiromizu, Kanoya, Kagoshima 891-2393, Japan. y-takai@nifs-k.ac.jp.
Yohei
Y
Takai
Megumi
M
Ohta
Ryota
R
Akagi
Emika
E
Kato
Taku
T
Wakahara
Yasuo
Y
Kawakami
Tetsuo
T
Fukunaga
Hiroaki
H
Kanehisa
D015502:Absorptiometry, Photon; D000368:Aged; D000885:Anthropology, Physical; D000886:Anthropometry / Q000379:methods*; D005260:Female; D006801:Humans; D007564:Japan; D007866:Leg / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000000981:diagnostic imaging* / Q000502:physiology; D012044:Regression Analysis; D015203:Reproducibility of Results; D014463:Ultrasonography