title: Influence of extracurricular sport activities on body composition and physical fitness in boys: a 3-year longitudinal study.
abstract: OBJECTIVE
  To analyse the effect of extracurricular physical activities on fat mass accumulation and physical fitness during growth in early pubertal males.
  
  
  METHODS
  Longitudinal study.
  
  
  METHODS
  A total of 42 male children (9.4+/-1.4 years, Tanner I-II and 12.7+/-1.5 years, Tanner III-IV, before and after the 3.3 years follow-up, respectively), randomly sampled from the population of Gran Canaria (Spain), 26 of them physically active (PA, at least 3 h per week during 3 years) and 16 non-physically active (non-PA).
  
  
  METHODS
  Body composition (dual-energy X-ray absorptiometry), anthropometrics (body circumferences and skinfolds) and physical fitness variables (dynamic and isometric force, anaerobic capacity and maximal aerobic power) were determined in all subjects.
  
  
  RESULTS
  Both groups had comparable body sizes at the start and the end of the study. Body mass index increased with growth more in the PA than in the non-PA group (P<0.05). However, fat mass accumulation with growth was lower in the PA than in the non-PA (P<0.05). There was a positive relationship between the increment of total and trunkal fat mass, especially in non-active children (r2=0.93). In contrast, there was an inverse relationship between the total lean mass growth and the accumulation of total and regional fat mass (r=-0.37 to -0.41, all P<0.05). Physical fitness was maintained in the PA, while it worsened in the non-PA children.
  
  
  CONCLUSIONS
  Without any dietary intervention, children who regularly participate in at least 3 h per week of sports activities are more protected against total and regional fat mass accumulation. They also increase their total lean and bone mass to a greater extent than children who do not participate in extracurricular sport activities. In addition, PA children maintain their physical fitness during growth, while it deteriorates in the non-PA children.
authors.affiliation: Department of Physical Education, University of Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Canary Island, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Ara
authors.forename: G
authors.initials: G
authors.lastname: Vicente-Rodriguez
authors.forename: J
authors.initials: J
authors.lastname: Perez-Gomez
authors.forename: J
authors.initials: J
authors.lastname: Jimenez-Ramirez
authors.forename: J A
authors.initials: JA
authors.lastname: Serrano-Sanchez
authors.forename: C
authors.initials: C
authors.lastname: Dorado
authors.forename: J A L
authors.initials: JA
authors.lastname: Calbet
mesh_terms: D015502:Absorptiometry, Photon; D000273:Adipose Tissue / Q000502:physiology; D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology; D000886:Anthropometry / Q000379:methods; D001823:Body Composition / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D015992:Body Mass Index; D002648:Child; D005080:Exercise Test / Q000379:methods; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010809:Physical Fitness / Q000502:physiology*; D013177:Sports / Q000502:physiology*; D015430:Weight Gain / Q000502:physiology