title: Rectus femoris (RF) ultrasound for the assessment of muscle mass in older people.
abstract: BACKGROUND
  Simple and reliable methods to evaluate muscle mass in older people are lacking.
  
  
  OBJECTIVE
  To evaluate ultrasound as a measure of RF muscle mass and quality in healthy subjects of different ages and gender, assessing its concordance with dual energy X-ray densitometry (DEXA) and association with muscle strength and walking capacity.
  
  
  METHODS
  We selected 54 adults of both genders, aged 20-55 years and 51 adults older than 60 years. Ultrasound images of the RF were obtained at the mid-thigh to measure its thickness and ultrasonographic density using a GE Logiq e equipment. Body composition was assessed by DEXA. Quadriceps isometric strength and 12 minutes' walk were also measured and gender specific t scores for older adults were calculated using the values obtained in adults.
  
  
  RESULTS
  RF ultrasound measurements correlated significantly with lean body mass assessed by DEXA (Double energy X-ray absorptiometry). The concordance between both measures was also adequate. Older people had lower muscle mass and worse ultrasound parameters than adults. Older males with a t score for quadriceps strength of -2 or less, had a significantly higher RF grayscale density. Older males with a 12 minutes' walk t score of -2 or less and old males and females with a walking speed of 1m/s or less had a lower RF thickness.
  
  
  CONCLUSIONS
  There is a good concordance between RF ultrasound and DEXA.
  
  
  CONCLUSIONS
  Assessment of RF using ultrasound appears to be a reliable and accurate method to evaluate muscle mass in older people.
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile.
authors.forename: Juan
authors.initials: J
authors.lastname: Berger
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile. Electronic address: dbunout@inta.uchile.cl.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bunout
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile.
authors.forename: Gladys
authors.initials: G
authors.lastname: Barrera
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile.
authors.forename: María Pía
authors.initials: MP
authors.lastname: de la Maza
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile.
authors.forename: Sandra
authors.initials: S
authors.lastname: Henriquez
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile.
authors.forename: Laura
authors.initials: L
authors.lastname: Leiva
authors.affiliation: Institute of Nutrition and Food Technology, University of Chile, Chile.
authors.forename: Sandra
authors.initials: S
authors.lastname: Hirsch
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D001823:Body Composition / Q000502:physiology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging* / Q000502:physiology; D014463:Ultrasonography; D016138:Walking / Q000502:physiology*
keywords: Rectus femoris; Sarcopenia; Ultrasound