title: Assessing Fatigability in the Lab and in Daily Life in Older Adults With Osteoarthritis Using Perceived, Performance, and Ecological Measures.
abstract: Fatigue in older adults is associated with functional decline and reduced participation in daily life; however, it is not well characterized. Examining fatigue within activity performance, or "fatigability," is a recommended approach to begin to understand fatigue and its underlying mechanisms. This study examined the construct validity of lab-based measures of fatigability and compared these measures with fatigability in daily life (termed ecological fatigability).
  
  
  
  Participants with osteoarthritis and fatigue (n = 163) underwent laboratory assessments, completed questionnaires, and wore accelerometers for 7 days while tracking symptoms and behaviors. Lab-based fatigability measures were quantified using the 6-minute walk test. Perceived fatigability was assessed by asking participants before and after the test to report: (i) fatigue severity and (ii) perceived exertion. Performance fatigability was calculated using change in walking speed divided by total distance walked. Ecological fatigability was calculated from the 7-day assessment in which fatigue severity was reported five times a day and physical activity was continuously measured. Additional ecological measures (eg, self-pacing) were examined.
  
  
  
  Lab-based perceived and performance fatigability measures were highly inter-correlated, moderately correlated with gait speed and metabolic measures, and weakly correlated with physical activity. Although ecological fatigability was weakly correlated with lab-based measures, participants with high fatigability on lab-based measures demonstrated more self-pacing behaviors than participants with low fatigability.
  
  
  
  Lab-based fatigability measures are related to physical capacity measured both in the lab and daily life. Lab-based fatigability measures provide important information regarding daily life fatigability useful for future intervention development.
authors: Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor. sumurphy@umich.edu.|Veterans Affairs Ann Arbor Health Care System, Geriatric Research, Education and Clinical Center, Michigan.
authors: Susan L
authors: SL
authors: Murphy
authors: Department of Physical Medicine and Rehabilitation, University of Michigan, Ann Arbor.
authors: Anna L
authors: AL
authors: Kratz
authors: Mrs. T.H. Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles. sumurphy@umich.edu.
authors: Stacey L
authors: SL
authors: Schepens Niemiec
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D017079:Exercise Tolerance / Q000502:physiology; D005221:Fatigue / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008297:Male; D010003:Osteoarthritis / Q000150:complications* / Q000503:physiopathology* / Q000523:psychology; D012649:Self Concept; D011795:Surveys and Questionnaires; D000072797:Walking Speed
keywords: Exertion; Fatigue; Frail; Physical activity