title: In search of lost time: When people undertake a new exercise program, where does the time come from? A randomized controlled trial.
abstract: OBJECTIVE
  The objective of this study was to investigate changes in use of time when undertaking a structured exercise program.
  
  
  METHODS
  This study used a randomized, multi-arm, controlled trial design.
  
  
  METHODS
  A total of 129 insufficiently active adults aged 18-60 years were recruited and randomly allocated to one of three groups, a Moderate or Extensive six-week exercise group (150 and 300 additional minutes of exercise per week, respectively) or a Control group. Prescribed exercise was accumulated through both group and individual sessions. Use of time was measured at baseline and end-program using the Multimedia Activity Recall for Children and Adults, a computerized 24-h recall instrument. Daily minutes of activity in activity domains and energy expenditure zones were determined.
  
  
  RESULTS
  Relative to changes in the control group, daily time spent in the physical activity [F (2, 108)=20.21, p<0.001] and Active Transport [F (2, 108)=3.71, p=0.03] time use domains significantly increased in the intervention groups by 21-45 min/day. Comparatively, the intervention groups spent significantly less time watching television [F (2, 108)=5.02, p=0.008; -50-52 min/day], relative to Controls. Additionally, time spent in the moderate to vigorous energy expenditure zone had significantly increased in the intervention groups by end-program [F (2, 108)=6.35, p=0.002; 48-50 min/day], relative to Controls.
  
  
  CONCLUSIONS
  This study is the first to comprehensively map changes in time use across an exercise program. The results suggest that exercise interventions should be mindful not only of compliance but also of "isotemporal displacement" of behaviors.
authors.affiliation: Centre for Research on Exercise, Physical Activity and Health, School of Human Movement Studies, The University of Queensland, St Lucia, Brisbane, Queensland, Australia; Health and Use of Time (HUT) Group, Sansom Institute for Health Research, University of South Australia, Australia. Electronic address: s.gomersall1@uq.edu.au.
authors.forename: Sjaan R
authors.initials: SR
authors.lastname: Gomersall
authors.affiliation: Exercise for Health and Human Performance, Sansom Institute for Health Research, University of South Australia, Australia.
authors.forename: Kevin
authors.initials: K
authors.lastname: Norton
authors.affiliation: Health and Use of Time (HUT) Group, Sansom Institute for Health Research, University of South Australia, Australia.
authors.forename: Carol
authors.initials: C
authors.lastname: Maher
authors.affiliation: International Centre for Allied Health Evidence (iCAHE), School of Health Science, University of South Australia, Australia.
authors.forename: Coralie
authors.initials: C
authors.lastname: English
authors.affiliation: Health and Use of Time (HUT) Group, Sansom Institute for Health Research, University of South Australia, Australia.
authors.forename: Tim S
authors.initials: TS
authors.lastname: Olds
mesh_terms: D000293:Adolescent; D000328:Adult; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D057185:Sedentary Behavior; D013690:Television; D013997:Time Factors; D014186:Transportation; D018910:Video Games; D055815:Young Adult
keywords: Energy expenditure; Exercise; Physical activity; Randomized controlled trial; Use of time