title: Contractile fatigue of the quadriceps muscle predicts improvement in exercise performance after pulmonary rehabilitation.
abstract: BACKGROUND
  We hypothesized that among patients with chronic obstructive pulmonary disease, those who develop quadriceps contractile fatigue (QCF) after exhaustive submaximal cycle exercise would have a greater response to exercise training than those who do not develop QCF (NQCF).
  
  
  METHODS
  Patients (N = 132) had measurement of QCF at baseline. Six-minute walk distance (6 MWD), maximal incremental cycle exercise testing, and quality of life measured by the Chronic Respiratory Questionnaire were obtained before and after pulmonary rehabilitation (PR).
  
  
  RESULTS
  Eighty of the 132 patients (60.6%) developed QCF following constant workload exhaustive cycle exercise. Patients who developed QCF had a significantly greater improvement in 6 MWD following PR (45.3 ± 45.2 m) than those who did not (27.5 ± 45.7 m; P= .032). When baseline differences between patients who developed QCF and NQCF were accounted for, the difference in 6 MWD remained significant. Patients who developed QCF were not more likely to identify leg fatigue as the factor limiting exercise (56.2% of QCF group stated that leg fatigue was the limiting factor compared with 47.9% in the NQCF group; P= .46). When baseline differences were accounted for, the symptom causing exercise termination was not a predictor of the response to PR.
  
  
  CONCLUSIONS
  Patients who were capable of developing QCF had a significantly greater improvement in 6 MWD after PR compared to NQCF. Symptoms causing exercise termination could not be used to predict the development of contractile fatigue or the response to PR.
authors.affiliation: Veteran Affairs Western New York Healthcare System (Dr Mador), and Division of Pulmonary, Critical Care and Sleep Medicine, State University of New York at Buffalo (Drs Mador, Mogri, and Patel), Buffalo, New York.
authors.forename: M Jeffery
authors.initials: MJ
authors.lastname: Mador
authors.forename: Mohammed
authors.initials: M
authors.lastname: Mogri
authors.forename: Anil
authors.initials: A
authors.lastname: Patel
mesh_terms: D000368:Aged; D000818:Animals; D005080:Exercise Test / Q000379:methods; D005081:Exercise Therapy / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue; D017063:Outcome Assessment, Health Care; D010101:Oxygen Consumption; D010807:Physical Endurance; D011237:Predictive Value of Tests; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000503:physiopathology / Q000523:psychology / Q000534:rehabilitation; D052097:Quadriceps Muscle / Q000503:physiopathology*; D011788:Quality of Life; D013147:Spirometry / Q000379:methods; D011795:Surveys and Questionnaires