title: Physical Improvement and Biological Maturity of Young Athletes (11-12 Years) with Systematic Training.
abstract: The aim of this study was to investigate the influence of systematic training in physical growth and biological maturity in prepubertal males and estimate how this affects the physical growth and skeletal maturity.
  
  
  
  177 primary school students of the fifth and sixth grade, from schools in Alexandroupolis, participated voluntarily in our study. Questionnaires were used in order to measure physical activity levels. The subjects were subdivided into two groups; control group (prepubertal, whose physical activity was the physical education of their school and which had never participated in systematic training, n = 95) and experimental group (prepubertal, whose weekly physical activity included physical education in their schools and additionally 3-4 training units organized training in various sports clubs in the city, n = 82). The following parameters were recorded: biological age measured by determination of skeletal age; bone density measured by ultrasound methods; anthropometric and morphological features such as height, body composition, selected diameters, circumferences and skinfolds; motor ability features.
  
  
  
  The experimental group exhibited older biological age (p = 0.033), higher bone density (p < 0.001), lower BMI and body fat (p < 0.001), better anthropometric features and higher performance throughout all motor ability tests (p < 0.05), compared to the control group.
  
  
  
  The present study demonstrates that systematic physical activity has a positive effect on both the physical and biological maturity of pre-pubertal children. This effect is mainly expressed in bone strengthening as a result of the increased bone density and in improvement of the kinetic skills of pupils who participated in organized extracurricular sport-activities.
authors.affiliation: Department of Orthopaedics and Traumatology, Democritus University of Thrace, Greece
authors.forename: Konstantinos E
authors.initials: KE
authors.lastname: Tilkeridis
authors.affiliation: Department of Orthopaedics and Traumatology, Democritus University of Thrace, Greece
authors.forename: Evaggelos F
authors.initials: EF
authors.lastname: Theodorou
authors.affiliation: Department of Kinesitherapy, Faculty of Public Health, University of Sofia, Bulgaria
authors.forename: Jannis V
authors.initials: JV
authors.lastname: Papathanasiou
authors.affiliation: Department of Orthopaedics and Traumatology, Democritus University of Thrace, Greece
authors.forename: Pelagia A
authors.initials: PA
authors.lastname: Chloropoulou
authors.affiliation: Department of Orthopaedics and Traumatology, Democritus University of Thrace, Greece
authors.forename: Grigorios A
authors.initials: GA
authors.lastname: Trypsianis
authors.affiliation: Physical Education and Sport Sciences, Democritus University of Thrace, Greece
authors.forename: Savvas P
authors.initials: SP
authors.lastname: Tokmakidis
authors.affiliation: Physical Education and Sport Sciences, Democritus University of Thrace, Greece
authors.forename: Konstantinos I
authors.initials: KI
authors.lastname: Kazakos
mesh_terms: D000293:Adolescent; D041923:Adolescent Development; D056352:Athletes; D001823:Body Composition / Q000502:physiology*; D015519:Bone Density / Q000502:physiology*; D016022:Case-Control Studies; D002648:Child; D002657:Child Development; D006801:Humans; D008297:Male; D010806:Physical Education and Training; D013334:Students