title: Distinguishing four components underlying physical activity: a new approach to using physical activity questionnaire data in old age.
abstract: BACKGROUND
  It is evident that physical activity has many benefits, but it often remains unclear which types of activity are optimal for health and functioning in old age. The aim of this methodological study was to propose a method for distinguishing four components underlying self reported physical activity of older adults: intensity, muscle strength, turning actions and mechanical strain.
  
  
  METHODS
  Physical activity was assessed by the validated LAPAQ questionnaire among 1699 older adults of the Longitudinal Aging Study Amsterdam. Based on expert consultation and literature review, the four component scores for several individual daily and sports activities were developed. Factor analysis was performed to confirm whether the developed components indeed measured different constructs of physical activity.
  
  
  RESULTS
  Based on the factor analyses, three components were distinguished: 1. intensity and muscle strength loaded on the same factor, 2. mechanical strain and 3. turning actions. Analyses in gender, age and activity level subgroups consistently distinguished three factors.
  
  
  CONCLUSIONS
  Future research using these components may contribute to our understanding of how specific daily and sports activities may have a different influence on health and physical functioning in old age.
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, the Netherlands. l.verweij@vumc.nl
authors.forename: Lisanne M
authors.initials: LM
authors.lastname: Verweij
authors.forename: Natasja M
authors.initials: NM
authors.lastname: van Schoor
authors.forename: Joost
authors.initials: J
authors.lastname: Dekker
authors.forename: Marjolein
authors.initials: M
authors.lastname: Visser
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D013314:Stress, Mechanical; D011795:Surveys and Questionnaires / Q000592:standards*