title: Sonographic Measurement of the Quadriceps Muscle in Patients With Chronic Obstructive Pulmonary Disease: Functional and Clinical Implications.
abstract: OBJECTIVE
  The purpose of this study was to determine the association between functionality as assessed by the 6-minute walking test (6MWT), maximal voluntary contraction of the quadriceps (MVCQ), and quadriceps thickness and echo intensity as measured by sonography, in patients with chronic obstructive pulmonary disease (COPD).
  
  
  METHODS
  Maximal voluntary contraction of the quadriceps and the thickness and echo intensity of the rectus femoris and vastus intermedius were evaluated in 20 patients with COPD. Functionality was assessed by the 6MWT. Differences between the evaluated muscles were determined by the Student t test. Pearson and Spearman rank correlation coefficients were used to analyze relationships between variables of interest, according to data characteristics. Finally, multivariate regression models were applied.
  
  
  RESULTS
  There was a positive correlation between MVCQ and rectus femoris and vastus intermedius thickness (r = 0.427; P = .030; r = 0.469; P= .018, respectively) and a negative correlation between MVCQ and rectus femoris and vastus intermedius echo intensity (r= -0.500; P= .012; r= -0.482; P= .016). No correlation was found between MVCQ and the 6MWT (r = 0.319; P = .085). Multivariate regression analysis showed that the rectus femoris echo intensity, vastus intermedius echo intensity, and vastus intermedius thickness explained 70% of the variance in the distance walked during the 6MWT.
  
  
  CONCLUSIONS
  These results indicate that, in patients with COPD, both quadriceps force and exercise capacity are associated with quantitative (thickness) and qualitative (echo intensity) characteristics of the quadriceps. Consequently, comprehensive assessments of peripheral muscles should simultaneously include both measurements.
authors.affiliation: Department of Physical Therapy, Faculty of Medicine, University of Chile, Santiago, Chile.|Laboratory of Biomechanics and Kinesiology, San José Hospital, Santiago, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Cruz-Montecinos
authors.affiliation: Pulmonary Rehabilitation Laboratory, San José Hospital, Santiago, Chile.|Department of Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Carlos
authors.initials: C
authors.lastname: Guajardo-Rojas
authors.affiliation: Department of Physical Therapy, Faculty of Medicine, University of Chile, Santiago, Chile.|Pulmonary Rehabilitation Laboratory, San José Hospital, Santiago, Chile.
authors.forename: Eloísa
authors.initials: E
authors.lastname: Montt
authors.affiliation: Department of Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Felipe
authors.initials: F
authors.lastname: Contreras-Briceño
authors.affiliation: Department of Physical Therapy, Faculty of Medicine, University of Chile, Santiago, Chile.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Torres-Castro
authors.affiliation: Department of Pulmonary Diseases, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Orlando
authors.initials: O
authors.lastname: Díaz
authors.affiliation: Department of Physiotherapy, School of Health Sciences, University of Malaga, and Andalucía Tech, Department of Physical Therapy and Disability, Research Institute of Biomedicine at Malaga, Group of Clinimetry, Malaga, Spain acuesta@uma.es.|School of Clinical Science, Faculty of Health Sciences, Queensland University of Technology, Brisbane, Queensland, Australia acuesta@uma.es.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cuesta-Vargas
mesh_terms: D000368:Aged; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D014463:Ultrasonography
keywords: chronic obstructive pulmonary disease; echo intensity; musculoskeletal ultrasound; quadriceps; rectus femoris; sonography; vastus intermedius