title: The long-term efficacy of two computer-tailored physical activity interventions for older adults: main effects and mediators.
abstract: OBJECTIVE
  Low-cost (e.g., computer-tailored) interventions with sustained effects are needed to increase and maintain physical activity in older adults. This study examined the long-term efficacy of 2 computer-tailored physical activity interventions for older adults and its psychosocial and environmental mediators.
  
  
  METHODS
  A clustered randomized controlled trial (N = 1,971) was conducted that included 3 research arms: (a) basic computer-tailored print intervention, targeting psychosocial mediators; (b) environmentally computer-tailored print intervention, targeting psychosocial and environmental mediators; and (c) no-intervention control group. Interventions were developed using the intervention mapping approach and consisted of 3 computer-tailored letters delivered over 4 months. Questionnaires assessed the study outcomes (i.e., total weekly days and total weekly minutes of physical activity) at baseline and 12 months. Potential mediators (i.e., awareness, attitude, self-efficacy, intention, social influence, intrinsic motivation, self-regulation, and perceived environment) were assessed at baseline and at 3 or 6 months.
  
  
  RESULTS
  Multilevel regression analyses revealed that both interventions significantly changed total weekly days of physical activity compared with the control group, but only the environmentally computer-tailored print intervention significantly changed weekly minutes of physical activity. Multiple mediation models showed that the effects of both interventions on weekly days of physical activity were mediated by changes in awareness and intention.
  
  
  CONCLUSIONS
  Computer-tailored interventions were effective in inducing long-term behavioral changes in physical activity behavior of older adults. Awareness and intention were found to be important mediators of changing daily physical activity and should be included in future computer-tailored intervention studies.
authors.affiliation: Department of Psychology, Open University of the Netherlands, Heerlen, the Netherlands. mm.vanstralen@vumc.nl
authors.forename: Maartje M
authors.initials: MM
authors.lastname: van Stralen
authors.forename: Hein
authors.initials: H
authors.lastname: de Vries
authors.forename: Aart N
authors.initials: AN
authors.lastname: Mudde
authors.forename: Catherine
authors.initials: C
authors.lastname: Bolman
authors.forename: Lilian
authors.initials: L
authors.lastname: Lechner
mesh_terms: D000368:Aged; D015444:Exercise / Q000523:psychology*; D015438:Health Behavior; D058015:Health Communication; D006293:Health Promotion; D006801:Humans; D033182:Intention; D008875:Middle Aged; D009042:Motivation; D009043:Motor Activity; D011795:Surveys and Questionnaires; D013813:Therapy, Computer-Assisted