title: The contribution of peripheral muscle function to shuttle walking performance in patients with chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  The contribution of muscle strength and mass to incremental and endurance walking performance in chronic obstructive pulmonary disease (COPD) is unknown. This study analyzes the relationship between field incremental and endurance walking performance and indices of peripheral muscle mass and strength.
  
  
  METHODS
  Eighty-five stable COPD patients (53 males; mean [SD] age = 67 [9] years; mean [SD] forced expiratory volume in 1 second [FEV1] = 35 [14] [% predicted]) were studied prior to participation in pulmonary rehabilitation. Isometric quadriceps and handgrip strength were measured. Total body and lower limb lean muscle mass were estimated using dual energy x-ray absorptiometry. Exercise performance was measured using the incremental shuttle walk test (ISWT) and the endurance (ESWT) shuttle walk test.
  
  
  RESULTS
  ISWT was related to muscle strength (r = 0.467, P </= .001) but not to whole body or lower limb lean mass. There was no association between muscle strength or mass and ESWT. In a multivariate linear regression analysis, the only variables significantly contributing to ISWT were age (P < .001), FEV1 (% predicted) (P < .001) and quadriceps strength (P < .001). Variables contributing to ESWT were FEV1 (% predicted) (P < .001) and ISWT performance (P < .001).
  
  
  CONCLUSIONS
  We conclude that muscle strength is related to incremental but not endurance shuttle walking performance. Muscle mass and strength are not synonymous in their effects on exercise performance in patients with COPD.
authors.affiliation: Institute for Lung Health, Department of Respiratory Medicine, Glenfield Hospital, Leicester, UK. michael.steiner@uhl-tr.nhs.uk
authors.forename: Michael C
authors.initials: MC
authors.lastname: Steiner
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Singh
authors.forename: Michael D L
authors.initials: MD
authors.lastname: Morgan
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000368:Aged; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D015331:Cohort Studies; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D018908:Muscle Weakness / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000534:rehabilitation*; D016138:Walking / Q000502:physiology*