title: Skeletal muscle quality assessed from echo intensity is associated with muscle strength of middle-aged and elderly persons.
abstract: Enhanced echo intensity (EI) on an ultrasound image of skeletal muscle indicates changes in muscle quality, including increases in intramuscular fibrous and adipose tissues. However, it is not known whether muscle quality assessed from the EI of computer-aided gray-scale analysis of an ultrasound image is associated with the muscle strength or body composition of a subject. The objectives of this study were to investigate whether muscle quality assessed from EI measured using gray-scale analysis is associated with muscle strength independently of age or muscle thickness (MT), and to examine the relationship between muscle EI and body composition. Ninety-two healthy women with a mean age of 70.4 ± 5.5 years (range, 51-87 years) dwelling in Kyoto, Japan, participated in the study. The MT, subcutaneous fat thickness (FT), and EI of the quadriceps femoris on the right extremity were assessed from transverse ultrasound images. Knee extensor isometric strength was used as a measure of the quadriceps femoris muscle strength. EI was significantly correlated with quadriceps strength independently of age or MT, and stepwise regression analysis revealed that MT and EI were independently associated with quadriceps strength. Importantly, EI showed no significant correlations with FT, percentage of body fat (%BF), or body mass index (BMI), while FT, BMI, and %BF did not significantly influence muscle strength. These data suggest that muscle quantity (i.e., MT) and muscle quality assessed from EI measured using computer-aided gray-scale analysis independently contribute to muscle strength in middle-aged and elderly persons.
authors.affiliation: Human Health Sciences, Graduate School of Medicine, Kyoto University, 53 Kawahara-cho Shogoin, Sakyo-ku, Kyoto 606-8507, Japan. y.fukumoto@fx5.ecs.kyoto-u.ac.jp
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Fukumoto
authors.forename: Tome
authors.initials: T
authors.lastname: Ikezoe
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Yamada
authors.forename: Rui
authors.initials: R
authors.lastname: Tsukagoshi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakamura
authors.forename: Natsuko
authors.initials: N
authors.lastname: Mori
authors.forename: Misaka
authors.initials: M
authors.lastname: Kimura
authors.forename: Noriaki
authors.initials: N
authors.lastname: Ichihashi
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D001823:Body Composition; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007564:Japan; D008875:Middle Aged; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging*; D012044:Regression Analysis; D014463:Ultrasonography