title: Sex-specific genetic effects in physical activity: results from a quantitative genetic analysis.
abstract: BACKGROUND
  The objective of this study is to present a model to estimate sex-specific genetic effects on physical activity (PA) levels and sedentary behaviour (SB) using three generation families.
  
  
  METHODS
  The sample consisted of 100 families covering three generations from Portugal. PA and SB were assessed via the International Physical Activity Questionnaire short form (IPAQ-SF). Sex-specific effects were assessed by genotype-by-sex interaction (GSI) models and sex-specific heritabilities. GSI effects and heterogeneity were tested in the residual environmental variance. SPSS 17 and SOLAR v. 4.1 were used in all computations.
  
  
  RESULTS
  The genetic component for PA and SB domains varied from low to moderate (11% to 46%), when analyzing both genders combined. We found GSI effects for vigorous PA (p = 0.02) and time spent watching television (WT) (p < 0.001) that showed significantly higher additive genetic variance estimates in males. The heterogeneity in the residual environmental variance was significant for moderate PA (p = 0.02), vigorous PA (p = 0.006) and total PA (p = 0.001). Sex-specific heritability estimates were significantly higher in males only for WT, with a male-to-female difference in heritability of 42.5 (95% confidence interval: 6.4, 70.4).
  
  
  CONCLUSIONS
  Low to moderate genetic effects on PA and SB traits were found. Results from the GSI model show that there are sex-specific effects in two phenotypes, VPA and WT with a stronger genetic influence in males.
authors.affiliation: University of Texas Rio Grande Valley, School of Medicine, South Texas Diabetes and Obesity Institute, Brownsville, Texas. Diego@uthscsa.edu.
authors.forename: Vincent P
authors.initials: VP
authors.lastname: Diego
authors.affiliation: Academic Department of Physical Education, Federal University of Technology - Parana, Curitiba - PR, Brazil. raquelchaves@utfpr.edu.br.|CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. raquelchaves@utfpr.edu.br.
authors.forename: Raquel Nichele
authors.initials: RN
authors.lastname: de Chaves
authors.affiliation: University of Texas Rio Grande Valley, School of Medicine, South Texas Diabetes and Obesity Institute, Brownsville, Texas. Blangero@uthscsa.edu.
authors.forename: John
authors.initials: J
authors.lastname: Blangero
authors.affiliation: CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. mcsouza85@hotmail.com.
authors.forename: Michele Caroline
authors.initials: MC
authors.lastname: de Souza
authors.affiliation: CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. d.monteiro.santos13@gmail.com.
authors.forename: Daniel
authors.initials: D
authors.lastname: Santos
authors.affiliation: CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. thayse_natacha@hotmail.com.
authors.forename: Thayse Natacha
authors.initials: TN
authors.lastname: Gomes
authors.affiliation: CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. fernandak.santos@hotmail.com.|Department of Physical Education and Sports Science, CAV, Federal University of Pernambuco, Vitória de Santo Antão, Brazil. fernandak.santos@hotmail.com.
authors.forename: Fernanda Karina
authors.initials: FK
authors.lastname: dos Santos
authors.affiliation: CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. ruigarg@fade.up.pt.
authors.forename: Rui
authors.initials: R
authors.lastname: Garganta
authors.affiliation: Pennington Biomedical Research Center, Baton Rouge, USA. peter.katzmarzyk@pbrc.edu.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Katzmarzyk
authors.affiliation: CIFI²D, Kinanthropometry Lab, Faculty of Sport, University of Porto, Porto, Portugal Faculty of Sports, University of Porto, Porto, Portugal. jmaia@fade.up.pt.
authors.forename: José A R
authors.initials: JA
authors.lastname: Maia
mesh_terms: D000704:Analysis of Variance; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D040582:Inheritance Patterns / Q000235:genetics; D016013:Likelihood Functions; D008297:Male; D008957:Models, Genetic; D009043:Motor Activity / Q000235:genetics*; D011174:Portugal; D057185:Sedentary Behavior; D012727:Sex Characteristics; D011795:Surveys and Questionnaires