title: Quadriceps weakness is related to exercise capacity in idiopathic pulmonary fibrosis.
abstract: OBJECTIVE
  In COPD, it has been shown that peripheral muscle dysfunction is a factor determining exercise intolerance. We examined the hypothesis that exercise capacity of patients with idiopathic pulmonary fibrosis (IPF) is, at least in part, determined by peripheral muscle dysfunction.
  
  
  METHODS
  Maximum oxygen uptake (V(O2)max) was evaluated in 41 consecutive patients with IPF, along with potential determinants of exercise capacity, both in the lungs and in the peripheral muscles.
  
  
  RESULTS
  Patients had reduced V(O2)max (893 +/- 314 mL, 46.0% predicted) and reduced quadriceps force (QF) [65% predicted]. Significant correlates of V(O2)max reduction were vital capacity (VC) [r = 0.79], total lung capacity (r = 0.64), diffusion capacity (r = 0.64), QF (r = 0.62), maximum expiratory pressure (r = 0.48), and Pa(O2) at rest (r = 0.33). In stepwise multiple regression analysis, VC and QF were independent predictors of V(O2)max. Furthermore, in subgroup analysis, QF was a significant contributing factor for V(O2)max in patients who discontinued exercise because of dyspnea and/or leg fatigue.
  
  
  CONCLUSIONS
  We conclude that QF is a predictor of exercise capacity in IPF. Measures that improve muscle function might improve exercise tolerance.
authors.affiliation: Department of Respiratory Medicine and Allergy, Tosei General Hospital, 160 Nishioiwake-cho, Seto, Aichi, 489-8642 Japan. nishiyama_o@yahoo.co.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishiyama
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Taniguchi
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kondoh
authors.forename: Tomoki
authors.initials: T
authors.lastname: Kimura
authors.forename: Tomoya
authors.initials: T
authors.lastname: Ogawa
authors.forename: Fumiko
authors.initials: F
authors.lastname: Watanabe
authors.forename: Shinichi
authors.initials: S
authors.lastname: Arizono
mesh_terms: D000368:Aged; D015331:Cohort Studies; D018450:Disease Progression; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology*; D011237:Predictive Value of Tests; D011379:Prognosis; D011658:Pulmonary Fibrosis / Q000175:diagnosis* / Q000534:rehabilitation; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index