title: Perceived fatigability and metabolic and energetic responses to 6-minute walk test in older women.
abstract: OBJECTIVE
  To determine the relationship between perceived fatigability and oxygen consumption, carbon dioxide production, respiratory exchange ratio and the energy cost of walking in older women.
  
  
  METHODS
  Observational, cross-sectional study.
  
  
  METHODS
  Forty-eight community-dwelling older women were recruited from senior centres in Natal, Rio Grande do Norte, Brazil.
  
  
  METHODS
  Participants were evaluated in two different sessions. In the first session, sociodemographic and clinical factors were assessed and accelerometers were delivered. In the second session, the 6-minute walking test (6MWT) was performed and expired gases were analysed. Self-reported levels of fatigue were evaluated on a numerical scale from 1 ('extremely energetic') to 7 ('extremely tired'). Severity scores for perceived and performance fatigability were calculated as the ratio of change in performance and fatigue, respectively, with walking distance. The O2 cost of walking was based on the oxygen consumption rate and the 6MWT walking speed.
  
  
  RESULTS
  No correlation was found between the severity of perceived fatigability and metabolic measures. However, the severity of perceived fatigability was significantly correlated with greater O2 cost (r=0.579, P<0.01), physical activity (r=-0.654, P<0.01), walking distance (r=-0.712, P<0.01) and severity of performance fatigability (r=0.690, P<0.01).
  
  
  CONCLUSIONS
  Perceived fatigability was not directly associated with metabolic measures; however, greater severity of perceived fatigability was associated with an increase in the O2 cost of walking. Important relationships were also found between greater severity of perceived fatigability and poor functional fitness, high level of energy expenditure and lower level of physical activity.
authors.affiliation: Universidade Federal Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil. Electronic address: julianaferso@gmail.com.
authors.forename: J F deS
authors.initials: JF
authors.lastname: Barbosa
authors.affiliation: Department of Physiotherapy, Universidade Federal Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
authors.forename: S S
authors.initials: SS
authors.lastname: Bruno
authors.affiliation: Universidade Federal Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
authors.forename: N S O
authors.initials: NS
authors.lastname: Cruz
authors.affiliation: University of Sydney, Postgraduate Programme in Physical Therapy, Sydney, Australia.
authors.forename: J S
authors.initials: JS
authors.lastname: de Oliveira
authors.affiliation: Department of Physiotherapy, Universidade Estadual do Centro Oeste, Guarapuava, Rio Grande do Sul, Brazil.
authors.forename: J A
authors.initials: JA
authors.lastname: Ruaro
authors.affiliation: Department of Physiotherapy, Universidade Federal Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil.
authors.forename: R O
authors.initials: RO
authors.lastname: Guerra
mesh_terms: D061725:Accelerometry; D000368:Aged; D001938:Brazil; D002245:Carbon Dioxide / Q000378:metabolism; D003430:Cross-Sectional Studies; D004734:Energy Metabolism; D005080:Exercise Test; D005221:Fatigue / Q000175:diagnosis*; D005260:Female; D015577:Geriatric Assessment / Q000379:methods*; D006801:Humans; D010101:Oxygen Consumption / Q000502:physiology; D016138:Walking / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide
keywords: Ageing; Energy metabolism; Fatigue; Physical activity