title: Muscle fibre type shifting in the vastus lateralis of patients with COPD is associated with disease severity: a systematic review and meta-analysis.
abstract: BACKGROUND
  Skeletal muscle dysfunction is a common feature in chronic obstructive pulmonary disease (COPD) which is associated with intrinsic muscular abnormalities. One of the most consistently reported alterations is a shift from fibre type I to II in the vastus lateralis of these patients. Surprisingly, the relationship between this shift and the severity and phenotype of COPD remains unclear. A study was conducted to determine whether vastus lateralis muscle fibre type proportions are associated with COPD disease severity and to provide reference values for the proportions of fibre types in the vastus lateralis in COPD.
  
  
  METHODS
  A systematic review and a meta-analysis were conducted in which muscle fibre type data and markers of disease severity were collected from the literature.
  
  
  RESULTS
  The forced expiratory volume in 1 s (FEV(1)), the ratio of FEV(1) to forced vital capacity (FVC) and body mass index were positively associated with the proportion of type I fibres in COPD. A proportion of 51% for vastus lateralis fibre type I and 13% for fibre type IIX were calculated from the combined data as normal values for patients with typical GOLD stage 3-4 COPD aged 60-70 years. Based on these reference values, a proportion of fibre type I <27% and of fibre type IIX >29% were defined as pathologically abnormal.
  
  
  CONCLUSIONS
  This review sheds new light on the relationship between skeletal muscle abnormalities and important hallmarks of the disease in severe COPD, and identifies absence of data in GOLD stages 1-2. This review also provides reference values on fibre type composition for diagnostic purposes in COPD.
authors.affiliation: Department of Respiratory Medicine, NUTRIM, Maastricht University, P O Box 616, 6200 MD Maastricht, The Netherlands. h.gosker@pul.unimaas.nl
authors.forename: Harry R
authors.initials: HR
authors.lastname: Gosker
authors.forename: Maurice P
authors.initials: MP
authors.lastname: Zeegers
authors.forename: Emiel F M
authors.initials: EF
authors.lastname: Wouters
authors.forename: Annemie M W J
authors.initials: AM
authors.lastname: Schols
mesh_terms: D015415:Biomarkers; D015992:Body Mass Index; D002248:Carbon Monoxide / Q000097:blood; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D018656:Muscle Fibers, Fast-Twitch / Q000473:pathology*; D018657:Muscle Fibers, Slow-Twitch / Q000473:pathology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010100:Oxygen / Q000097:blood; D011379:Prognosis; D029424:Pulmonary Disease, Chronic Obstructive / Q000473:pathology*; D012132:Respiratory Muscles / Q000473:pathology*; D014797:Vital Capacity / Q000502:physiology
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide; D018995:Myosin Heavy Chains; D010100:Oxygen