title: The Extracellular to Intracellular Water Ratio in Upper Legs is Negatively Associated With Skeletal Muscle Strength and Gait Speed in Older People.
abstract: Skeletal muscles contain a large volume of water that is classified into intracellular (ICW) and extracellular (ECW) water fractions. Nuclear magnetic resonance-based biomarkers suggest that increased water T2 heterogeneities, as well as elevated water T2 relaxation in the quadriceps occurs in the elderly when compared with young adults. However, nuclear magnetic resonance is difficult to apply to a large-scale study or a clinical setting for sarcopenia and frailty screening. Segmental bioelectrical impedance spectroscopy is a unique tool used to assess the segmental ratio of ECW/ICW in the limbs. We evaluated 405 community-living people aged between 65 and 90 years. ECW and ICW in the upper legs were assessed by segmental bioelectrical impedance spectroscopy. Isometric knee extension strength, gait speed, and skeletal muscle mass were measured. Thigh ECW/ICW was negatively correlated with knee extension strength and gait speed (r = -.617 and -.431, respectively, p < .001) and increased with age (p < .001). Thigh ECW/ICW was a significant predictor of knee extension strength and gait speed independent of age, sex, body mass index, and skeletal muscle mass. Relative expansion of ECW against ICW in the thigh muscles is a factor in decreased muscle quality and a biomarker of muscle aging.
authors.affiliation: Department of Nutritional Science, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, Tokyo, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Graduate School of Science and Technology, Kyoto Institute of Technology, Kyoto, Japan.|Senior Citizen's Welfare Section, Kameoka City Government, Kameoka, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Department of Business Administration and.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Yokoyama
authors.affiliation: Department of Health and Sports Sciences, Kyoto Gakuen University, Kameoka, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Watanabe
authors.affiliation: Department of Health and Sports Sciences, Kyoto Gakuen University, Kameoka, Japan.
authors.forename: Motoko
authors.initials: M
authors.lastname: Miyake
authors.affiliation: Faculty of Nursing, Doshisha Women's College of Liberal Arts, Kyotanabe, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Yamagata
authors.affiliation: Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tokyo, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Health and Sports Sciences, Kyoto Gakuen University, Kameoka, Japan.
authors.forename: Misaka
authors.initials: M
authors.lastname: Kimura
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001834:Body Water; D045604:Extracellular Fluid; D005260:Female; D006801:Humans; D007424:Intracellular Fluid; D008297:Male; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000502:physiology*; D013848:Thigh; D000072797:Walking Speed
keywords: Bioelectrical impedance spectroscopy; Muscle quality; Muscle strength; Water fraction