title: Associations between physical activity dose and health-related quality of life.
abstract: OBJECTIVE
  Although the beneficial effects of participation in regular physical activity (PA) are widely accepted, dose-response relationships between PA and health-related quality of life (HRQOL) remain unclear.
  
  
  METHODS
  We examined relationships between frequency, duration, and intensity of PA and HRQOL among 175,850 adults using data from the 2001 BRFSS. Logistic regression was used to obtain odds ratios (OR) and 95% confidence intervals (CI) adjusted for age, gender, race/ethnicity, education, smoking status, and body mass index.
  
  
  RESULTS
  The age-standardized prevalence (standard error) of 14 or more unhealthy (physical or mental) days during the previous 30 d was 28.4% (0.50) among physically inactive adults, 16.7% (0.27) among those with insufficient levels of PA, and 14.7% (0.22) among adults who met recommended levels. Overall, participation in no moderate PA (OR: 2.02; 95% CI: 1.85-2.21) was associated with an increased likelihood of having 14 or more unhealthy days. Also for moderate PA, participation every day of the week (5-6 d x wk as referent) (OR: 1.35; 1.26-1.46) was associated with an increased likelihood of 14 or more unhealthy days, as was participation for periods < 20 min (OR: 1.43; 95% CI: 1.30-1.58) or > or = 90 min (OR: 1.22; 95% CI: 1.14-1.31) per day (30-59 min x d as referent). Similar associations were observed for participation in vigorous PA.
  
  
  CONCLUSIONS
  Persons achieving recommended levels of PA were more likely to report fewer unhealthy days compared with inactive and insufficiently active persons; however, participation in daily moderate or vigorous PA and participation in very short (< 20 min x d) or extended ( > or = 90 min x d) periods of PA was associated with poorer HRQOL. Further research examining the relationship between the dose of PA and HRQOL as well as other health outcomes is needed.
authors.affiliation: Division of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA. dbrown6@cdc.gov
authors.forename: David W
authors.initials: DW
authors.lastname: Brown
authors.forename: David R
authors.initials: DR
authors.lastname: Brown
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Heath
authors.forename: Lina
authors.initials: L
authors.lastname: Balluz
authors.forename: Wayne H
authors.initials: WH
authors.lastname: Giles
authors.forename: Earl S
authors.initials: ES
authors.lastname: Ford
authors.forename: Ali H
authors.initials: AH
authors.lastname: Mokdad
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D015444:Exercise / Q000502:physiology / Q000523:psychology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D011795:Surveys and Questionnaires; D013997:Time Factors; D014481:United States