title: Initial Validation of the Activity Choice Index Among Overweight Women.
abstract: OBJECTIVE
  This prospective study was designed to evaluate psychometric properties of the Activity Choice Index (ACI), a measure for assessing one's choice to engage in more effortful, physically active behaviors in the course of daily routines over less-demanding, sedentary behaviors, in a sample of overweight women.
  
  
  METHODS
  The sample included 192 overweight women (Mage = 37.6 ± 7 years; Mbody mass index = 31.6 ± 4.1 kg/m(2)) who were assessed at baseline and 12 months after beginning a weight management intervention.
  
  
  RESULTS
  The unidimensional factor structure was confirmed for the 6-item version of the ACI. Group invariance and temporal invariance were also established. Moreover, ACI scores were positively correlated with self-reported physical activity (as measured by the 7-Day Physical Activity Recall), daily pedometer steps, and 3-day average accelerometer counts.
  
  
  CONCLUSIONS
  This preliminary investigation provides evidence that a relatively brief self-report instrument for assessing lifestyle physical activity choices has strong psychometric characteristics although convergent evidence is limited. The ACI has potential utility for researchers and practitioners aiming to quantify, or track change in, physical activity in everyday, free-living conditions. This early investigation sets the stage for future research to further delineate and strengthen the measurement of the ACI construct.
authors.affiliation: a University of Illinois at Urbana-Champaign.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Mullen
authors.affiliation: b University of Lisbon.|c Lusophone University of Humanities and Technologies.
authors.forename: Marlene N
authors.initials: MN
authors.lastname: Silva
authors.affiliation: b University of Lisbon.
authors.forename: Luís B
authors.initials: LB
authors.lastname: Sardinha
authors.affiliation: b University of Lisbon.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Teixeira
mesh_terms: D061725:Accelerometry; D056044:Actigraphy; D000328:Adult; D002755:Choice Behavior; D005260:Female; D006801:Humans; D008875:Middle Aged; D050177:Overweight / Q000503:physiopathology; D005082:Physical Exertion / Q000502:physiology*; D011446:Prospective Studies; D011594:Psychometrics; D057185:Sedentary Behavior; D057566:Self Report; D011795:Surveys and Questionnaires; D016138:Walking / Q000502:physiology
keywords: Accelerometry; measurement; physical activity; physical activity assessment