title: Impact of a physical activity intervention on adolescents' subjective sleep quality: a pilot study.
abstract: BACKGROUND
  The aim of this pilot study was to examine the impact of a brief physical activity intervention on adolescents' subjective sleep quality. Cross-sectional studies indicate that physically active adolescents have better subjective sleep quality than those with more sedentary habits. However, less is known about the effectiveness of physical activity interventions in improving adolescents' subjective sleep quality.
  
  
  METHODS
  In a three-week physical activity intervention, four Icelandic upper secondary schools were randomized to either an intervention group with pedometers and step diaries or a control group without pedometers and diaries. Out of 84, a total of 53 students, aged 15-16 years, provided complete data or a minimum of two days step data (out of three possible) as well as sleep quality measures at baseline and follow-up. Subjective sleep quality, the primary outcome in this study, was assessed with four individual items: sleep onset latency, nightly awakenings, general sleep quality, and sleep sufficiency. Daily steps were assessed with Yamax CW-701 pedometers.
  
  
  RESULTS
  The intervention group ( n = 26) had significantly higher average step-count ( p = 0.03, partial η2= 0.093) compared to the control group ( n = 27) at follow-up. Subjective sleep quality improved ( p = 0.02, partial η2= 0.203) over time in the intervention group but not in the control group.
  
  
  CONCLUSIONS
  Brief physical activity interventions based on pedometers and step diaries may be effective in improving adolescents' subjective sleep quality. This has important public health relevance as the intervention can easily be disseminated and incorporated into school curricula.
authors.affiliation: 1. Department of Psychology, School of Business, Reykjavik University, Iceland.|2. Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy at University of Gothenburg, Sweden.
authors.forename: Birna
authors.initials: B
authors.lastname: Baldursdottir
authors.affiliation: 1. Department of Psychology, School of Business, Reykjavik University, Iceland.|3. ICSRA (Icelandic Centre for Social Research and Analysis), Reykjavik University, Iceland.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Taehtinen
authors.affiliation: 1. Department of Psychology, School of Business, Reykjavik University, Iceland.|3. ICSRA (Icelandic Centre for Social Research and Analysis), Reykjavik University, Iceland.|7. Department of Health & Behavior Studies, Teachers College, Columbia University, New York, NY, USA.
authors.forename: Inga Dora
authors.initials: ID
authors.lastname: Sigfusdottir
authors.affiliation: 2. Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy at University of Gothenburg, Sweden.|5. Department of Biomedicine and Public Health, School of Health and Education, University of Skövde, Sweden.|6. Department of Community Medicine, UiT The Arctic University of Norway, Tromsø, Norway.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Krettek
authors.affiliation: 1. Department of Psychology, School of Business, Reykjavik University, Iceland.|4. Department of Oncological Sciences, Mount Sinai School of Medicine, New York, NY, USA.
authors.forename: Heiddis B
authors.initials: HB
authors.lastname: Valdimarsdottir
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D007055:Iceland; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D010865:Pilot Projects; D011634:Public Health; D011897:Random Allocation; D012574:Schools; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires; D016138:Walking / Q000502:physiology*
keywords: adolescents & youth; health promotion; physical activity; public health; school setting; sleep quality