title: Seasonal variation in adult leisure-time physical activity.
abstract: OBJECTIVE
  To determine the effect of season on self-reported leisure-time physical activity (LTPA) behaviors of Michigan adults.
  
  
  METHODS
  Data were obtained from the 1996 Michigan Behavioral Risk Factor Survey conducted throughout the year. Survey respondents were considered active if they reported participating in at least one LTPA during the past month. Complete information regarding type, frequency, and duration of up to two LTPA was available on 2843 adults (1635 women and 1208 men). Four seasons were defined as winter (January-March; N = 677), spring (April-June; N = 759), summer (July-September; N = 760), and fall (October-December; N = 647). Total weekly leisure-time energy expenditure was quantified (kcal x kg-1 x wk-1) from MET intensities, duration, and frequency of activity sessions per week. Seasonal differences were identified using ANOVA.
  
  
  RESULTS
  Average (+/-SEM) weekly leisure time energy expenditure was significantly greater (P < 0.001) during spring (17.5 +/- 0.8 kcal x kg-1 x wk-1) and summer (17.5 +/- 0.7 kcal.kg-1.wk-1) compared with winter (14.8 +/- 0.7 kcal x kg-1 x wk-1) and fall (15.0 +/- 0.7 kcal x kg-1 x wk-1). Duration of the first activity was significantly greater (P < 0.05) in summer (58.6 +/- 1.6 min) compared with winter (53.4 +/- 1.8 min). However, intensity (4.6 +/- 0.1 METs) and frequency (3.1 +/- 0.1 sessions per week) of the first activity did not differ among seasons. A second activity was performed by 1319 (46.4%) of active individuals and was more common in the spring (46.8%) and summer (54.5%) compared with fall (42.6%) and winter (39.4%) (chi2 = 31.0; P < 0.01). When both active and inactive subjects are considered, the Healthy People 2010 recommendation for moderate physical activity was met only during spring and summer.
  
  
  CONCLUSIONS
  Weekly leisure-time energy expenditure averaged approximately 15-20% higher during spring and summer. Much of this difference was due to active respondents participating in a second activity during these seasons.
authors.affiliation: Department of Kinesiology, Michigan State University, East Lansing 48824, USA. jimpiv@msu.edu
authors.forename: James M
authors.initials: JM
authors.lastname: Pivarnik
authors.forename: Mathew J
authors.initials: MJ
authors.lastname: Reeves
authors.forename: Ann P
authors.initials: AP
authors.lastname: Rafferty
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D015438:Health Behavior; D006306:Health Surveys; D006801:Humans; D008019:Life Style; D008297:Male; D011998:Recreation; D012621:Seasons