title: Dose-response effects of a Web-based physical activity program on body composition and metabolic health in inactive older adults: additional analyses of a randomized controlled trial.
abstract: BACKGROUND
  Low physical activity is a major risk factor for several age-related diseases. Recently, we showed in a randomized controlled trial that a 12-week Web-based intervention (Philips DirectLife) to increase physical activity was effective in increasing physical activity levels and metabolic health in an inactive population aged 60-70 years.
  
  
  OBJECTIVE
  The goal of this paper was to assess how many participants successfully reached the physical activity level as targeted by the intervention and what the effects of the intervention on body composition and metabolic health in these successful individuals were to provide insight in the maximum attainable effect of the intervention.
  
  
  METHODS
  Among the 235 participants in a randomized controlled trial of the Actief en Gezond Oud (AGO) study, we assessed the effects of the intervention on metabolic parameters in those who had successfully reached their personalized physical activity target compared with the entire intervention group. Furthermore, we studied the dose-response effect of increase in physical activity on metabolic outcome within the intervention group.
  
  
  RESULTS
  Of the intervention group, 50 of 119 (42.0%) participants successfully reached the physical activity target (corresponding to a 10% increased daily physical activity on average). This group showed markedly higher effects of the intervention compared to the entire intervention group, with greater decreases in body weight (2.74 vs 1.49 kg), waist circumference (3.74 vs 2.33 cm), insulin resistance (HOMA index: 0.23 vs 0.20), and in cholesterol/HDL ratio (0.39 vs 0.20) and Framingham risk score (0.90% vs 0.54%). We found that men compared to women were more likely to be successful. The dose-response analysis showed that there was a significant association between increase in minutes spent in moderate-to-vigorous activity and body weight loss, BMI reduction, waist circumference reduction, HDL cholesterol increasing, and cholesterol/HDL ratio lowering.
  
  
  CONCLUSIONS
  Of the intervention group, 42.0% (50/119) reached their daily physical activity end goal, which was associated with a markedly better effect on body composition and metabolic health compared to the effect in the entire intervention group. In this population, men are more likely to be successful in increasing physical activity. Findings demonstrate that improving the effect of such physical activity interventions requires finding new ways to increase the proportion of the population reaching the targeted goal.
  
  
  BACKGROUND
  Dutch Trial Registry: NTR 3045; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=3045 (Archived by WebCite at http://www.webcitation.org/6KPw52dCc).
authors.affiliation: Department of Gerontology and Geriatrics, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: David P
authors.identifier: http://orcid.org/0000-0003-1360-8878
authors.initials: DP
authors.lastname: Vroege
authors.forename: Carolien A
authors.identifier: http://orcid.org/0000-0002-4999-841X
authors.initials: CA
authors.lastname: Wijsman
authors.forename: Karen
authors.identifier: http://orcid.org/0000-0002-7216-3162
authors.initials: K
authors.lastname: Broekhuizen
authors.forename: Anton J M
authors.identifier: http://orcid.org/0000-0001-9314-123X
authors.initials: AJ
authors.lastname: de Craen
authors.forename: Diana
authors.identifier: http://orcid.org/0000-0001-8526-7748
authors.initials: D
authors.lastname: van Heemst
authors.forename: Frans J G
authors.identifier: http://orcid.org/0000-0002-7243-0179
authors.initials: FJ
authors.lastname: van der Ouderaa
authors.forename: Willem
authors.identifier: http://orcid.org/0000-0001-7136-6382
authors.initials: W
authors.lastname: van Mechelen
authors.forename: P Eline
authors.identifier: http://orcid.org/0000-0002-2875-4723
authors.initials: PE
authors.lastname: Slagboom
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0003-0935-7973
authors.initials: M
authors.lastname: Catt
authors.forename: Rudi G J
authors.identifier: http://orcid.org/0000-0002-0672-8372
authors.initials: RG
authors.lastname: Westendorp
authors.forename: Evert A L M
authors.identifier: http://orcid.org/0000-0001-9227-8234
authors.initials: EA
authors.lastname: Verhagen
authors.forename: Simon P
authors.identifier: http://orcid.org/0000-0003-3106-3568
authors.initials: SP
authors.lastname: Mooijaart
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D001823:Body Composition / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D020407:Internet; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D015431:Weight Loss
keywords: Internet; aging; metabolism; physical activity