title: Characteristics and determinants of endurance cycle ergometry and six-minute walk distance in patients with COPD.
abstract: BACKGROUND
  Exercise tolerance can be assessed by the cycle endurance test (CET) and six-minute walk test (6MWT) in patients with Chronic Obstructive Pulmonary Disease (COPD). We sought to investigate the characteristics of functional exercise performance and determinants of the CET and 6MWT in a large clinical cohort of COPD patients.
  
  
  METHODS
  A dataset of 2053 COPD patients (43% female, age: 66.9 ± 9.5 years, FEV1% predicted: 48.2 ± 23.2) was analyzed retrospectively. Patients underwent, amongst others, respiratory function evaluation; medical tests and questionnaires, one maximal incremental cycle test where peak work rate was determined and two functional exercise tests: a CET at 75% of peak work rate and 6MWT. A stepwise multiple linear regression was used to assess determinants.
  
  
  RESULTS
  On average, patients had impaired exercise tolerance (peak work rate: 56 ± 27% predicted, 6MWT: 69 ± 17% predicted). A total of 2002 patients had CET time of duration (CET-Tend) less than 20 min while only 51 (2.5%) of the patients achieved 20 min of CET-Tend . In former patients, the percent of predicted peak work rate achieved differed significantly between men (48 ± 21% predicted) and women (67 ± 31% predicted). In contrast, CET-Tend was longer in men (286 ± 174 s vs 250 ± 153 s, p < 0.001). Also, six minute walking distance (6MWD) was higher in men compared to women, both in absolute terms as in percent of predicted (443 m, 67%predicted vs 431 m, 72%predicted, p < 0.05). Gender was associated with the CET-Tend but BMI, FEV1 and FRC were related to the 6MWD highlighting the different determinants of exercise performance between CET and 6MWT.
  
  
  CONCLUSIONS
  CET-Tend is a valuable outcome of CET as it is related to multiple clinical aspects of disease severity in COPD. Gender difference should temper the interpretation of CET.
authors.affiliation: Department of Research & Education, CIRO+, Centre of Expertise for Chronic Organ Failure, Hornerheide 1, 6085 NM Horn, Eindhoven, Netherlands. vasilisandrianopoulos@ciro-horn.nl.
authors.forename: Vasileios
authors.initials: V
authors.lastname: Andrianopoulos
authors.forename: Scott S
authors.initials: SS
authors.lastname: Wagers
authors.forename: Miriam T J
authors.initials: MT
authors.lastname: Groenen
authors.forename: Lowie E
authors.initials: LE
authors.lastname: Vanfleteren
authors.forename: Frits M E
authors.initials: FM
authors.lastname: Franssen
authors.forename: Frank W J M
authors.initials: FW
authors.lastname: Smeenk
authors.forename: Ioannis
authors.initials: I
authors.lastname: Vogiatzis
authors.forename: Emiel F M
authors.initials: EF
authors.lastname: Wouters
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Spruit
mesh_terms: D000368:Aged; D015331:Cohort Studies; D016208:Databases, Factual; D016552:Ergometry / Q000379:methods*; D005080:Exercise Test / Q000379:methods; D005260:Female; D005541:Forced Expiratory Volume; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012129:Respiratory Function Tests; D013997:Time Factors; D014797:Vital Capacity; D016138:Walking / Q000502:physiology*