title: Physical activity intensities in youth: the effect of month of assessment.
abstract: BACKGROUND
  There is clear evidence that environmental factors play an important role regarding physical activity (PA) and sedentary behaviour (SB) in youth. This short report highlights seasonal differences in the amount and intensities of PA and SB, in Portuguese youth.
  
  
  METHODS
  Three hundred and eighty-seven participants (aged 14.7 ± 1.9 years), 220 girls, used the Actigraph GT1M accelerometer for 7 days (15-second epochs), between January and June in 2008. PA and SB differences were assessed using an ANCOVA.
  
  
  RESULTS
  Boys had significantly higher values of PA, with the exception of Light intensity. Girls were significantly more sedentary. PA intensities and SB changed significantly according to gender and month of assessment. SB (Gender F = 16.32, p < 0.001; Month F = 2.95, p < 0.013), Light PA (Gender F = 9.30, p = 0.002; Month F = 8.37, p < 0.001; Gender*Month F = 2.24, p = 0.050), Moderate PA (Gender F = 40.04, p < 0.001), Vigorous PA (Gender F = 32.89, p < 0.001; Month F = 2.56, p = 0.027). Both genders increased PA from winter to summer months and SB decreased.
  
  
  CONCLUSIONS
  Seasonality in PA intensities and SB suggest that interventions to promote PA and decrease SB must be tailored to take into consideration the month of the year they are going to be implemented and also gender characteristics.
authors.affiliation: CIAFEL (Research Centre in Physical Activity, Health and Leisure), Faculty of Sports .
authors.forename: Pedro
authors.initials: P
authors.lastname: Silva
authors.forename: André
authors.initials: A
authors.lastname: Seabra
authors.forename: Pedro
authors.initials: P
authors.lastname: Saint-Maurice
authors.forename: Luisa
authors.initials: L
authors.lastname: Soares-Miranda
authors.forename: Jorge
authors.initials: J
authors.lastname: Mota
mesh_terms: D056044:Actigraphy; D000293:Adolescent; D000704:Analysis of Variance; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D011174:Portugal; D012621:Seasons; D012727:Sex Characteristics