title: The HEART Mobile Phone Trial: The Partial Mediating Effects of Self-Efficacy on Physical Activity among Cardiac Patients.
abstract: BACKGROUND
  The ubiquitous use of mobile phones provides an ideal opportunity to deliver interventions to increase physical activity levels. Understanding potential mediators of such interventions is needed to increase their effectiveness. A recent randomized controlled trial of a mobile phone and Internet (mHealth) intervention was conducted in New Zealand to determine the effectiveness on exercise capacity and physical activity levels in addition to current cardiac rehabilitation (CR) services for people (n = 171) with ischemic heart disease. Significant intervention effect was observed for self-reported leisure-time physical activity and walking, but not peak oxygen uptake at 24 weeks. There was also significant improvement in self-efficacy.
  
  
  OBJECTIVE
  To evaluate the mediating effect of self-efficacy on physical activity levels in an mHealth delivered exercise CR program.
  
  
  METHODS
  Treatment evaluations were performed on the principle of intention to treat. Adjusted regression analyses were conducted to evaluate the main treatment effect on leisure-time physical activity and walking at 24 weeks, with and without change in self-efficacy as the mediator of interest.
  
  
  RESULTS
  Change in self-efficacy at 24 weeks significantly mediated the treatment effect on leisure-time physical activity by 13%, but only partially mediated the effect on walking by 4% at 24 weeks.
  
  
  CONCLUSIONS
  An mHealth intervention involving text messaging and Internet support had a positive treatment effect on leisure-time physical activity and walking at 24 weeks, and this effect was likely mediated through changes in self-efficacy. Future trials should examine other potential mediators related to this type of intervention.
authors.affiliation: National Institute for Health Innovation, University of Auckland , Auckland , New Zealand.
authors.forename: Ralph
authors.initials: R
authors.lastname: Maddison
authors.affiliation: National Institute for Health Innovation, University of Auckland , Auckland , New Zealand.
authors.forename: Leila
authors.initials: L
authors.lastname: Pfaeffli
authors.affiliation: Auckland City Hospital , Auckland , New Zealand.
authors.forename: Ralph
authors.initials: R
authors.lastname: Stewart
authors.affiliation: Epidemiology and Biostatistics, University of Auckland , Auckland , New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kerr
authors.affiliation: National Institute for Health Innovation, University of Auckland , Auckland , New Zealand.
authors.forename: Yannan
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: National Institute for Health Innovation, University of Auckland , Auckland , New Zealand.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Rawstorn
authors.affiliation: National Institute for Health Innovation, University of Auckland , Auckland , New Zealand.
authors.forename: Karen
authors.initials: K
authors.lastname: Carter
authors.affiliation: National Institute for Health Innovation, University of Auckland , Auckland , New Zealand.
authors.forename: Robyn
authors.initials: R
authors.lastname: Whittaker
keywords: behavior; exercise; mobile phones; self-efficacy