title: Anatomical cross-sectional area of the quadriceps femoris and sit-to-stand test score in middle-aged and elderly population: development of a predictive equation.
abstract: BACKGROUND
  Although the sit-to-stand (STS) test score has been shown to relate to the strength and size of the quadriceps femoris (QF) for elderly population, it is unknown whether this relationship is influenced by a posture (i.e., the trunk being allowed to stoop or not) during the STS test. The present study investigated the relationship between STS test score and QF anatomical cross-sectional area (ACSA) in the middle-aged and elderly population with regard to the difference in the posture during STS test, and aimed to develop an accurate predicting equation of the QF ACSA from the STS test score.
  
  
  METHODS
  105 males (40-81 years) and 113 females (41-79 years) participated in the present study, then the subjects were divided at random as validation and cross-validation groups. Mid-thigh QF ACSA was determined by magnetic resonance imaging. Subjects performed a 10-repeated STS as fast as possible in two conditions: (1) with the trunk being allowed to stoop during the sitting phases, and (2) kept upright throughout the test. A power index of the STS test score was calculated based on an equation obtained in a previous study using the time taken for each test condition, the thigh and shank lengths, and body mass. In the validation group (n = 109), a stepwise multiple linear regression analysis was performed to create a predictive model of the ACSA with sex, age, the STS time, and power for both conditions as independent variables. The formulated predictive equation was examined in the cross-validation group (n = 109).
  
  
  RESULTS
  In the validation group, a stepwise regression analysis revealed that STS power with upright trunk condition, sex, and age but not with the stooping condition, were selected as variables to predict QF ACSA (R (2) = 0.64, P < 0.001). There was no systematic error for the relationship between predicted and measured values in the cross-validation group.
  
  
  CONCLUSIONS
  These results indicate that STS test score with upright trunk condition is one of the indices of QF muscle size of the middle-aged and elderly population. The estimated predicting equation should be useful in clinical and practical settings for the health promotion.
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan. a-saito@aoni.waseda.jp.
authors.forename: Akira
authors.initials: A
authors.lastname: Saito
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.|Graduate School of Engineering and Science, Shibaura Institute of Technology, 307 Fukasaku, Minuma-ku, Saitama, Japan.|Research Fellow of Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, Japan.
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Ema
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Inami
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.|Research Fellow of Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, Japan.
authors.forename: Sumiaki
authors.initials: S
authors.lastname: Maeo
authors.affiliation: Graduate School of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Otsuka
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.|Institute of Advanced Active Aging Research, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Higuchi
authors.affiliation: School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu, Shinjuku-ku, Tokyo, Japan.
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Shibata
authors.affiliation: Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Kawakami
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D053580:Muscle Strength / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D052097:Quadriceps Muscle / Q000033:anatomy & histology* / Q000502:physiology
keywords: Aging; Magnetic resonance imaging; Multiple regression analysis; Muscle size; Trunk motion