title: Longitudinal influence of musculo-skeletal injuries and extra physical education on physical fitness in schoolchildren.
abstract: The aims of this study were to investigate if (A) injuries and (B) increased physical education (PE) influenced the development of physical fitness in schoolchildren. Simultaneously, to investigate if a possible PE effect was modified by sport participation outside school hours. This was a longitudinal controlled school-based study. Six schools with 270 min of PE (extra PE) and four schools with 90 min of PE were followed up for 2.5 years. In total, 1054 children were included for analysis (normal PE = 443, extra PE = 611). Development in fitness was analyzed using composite z-scores from six fitness tests measured four times. Information of injury and sport was derived from weekly automated mobile phone text messages surveying the presence of musculo-skeletal pain and organized sport participation. Injury and extra PE both influenced the development of physical fitness. Injury decreased development of physical fitness with -1.01 composite z-score units (95% CI: -1.57; -0.45). Extra PE increased physical fitness development with 0.80 (95% CI: 0.49; 1.10) composite z-score units. The influence of injury was not dependent on extra PE. No modifying effect was found by mean weekly sport participation outside school hours. In conclusion, extra PE had a positive effect, whereas injuries had a negative effect on physical fitness development in schoolchildren.
authors.affiliation: Centre of Research in Childhood Health, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.
authors.forename: C T
authors.initials: CT
authors.lastname: Rexen
authors.affiliation: National Institute of Public Health, University of Southern Denmark, København, Denmark.
authors.forename: A K
authors.initials: AK
authors.lastname: Ersbøll
authors.affiliation: Centre of Research in Childhood Health, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.|Institute of Regional Health Services Research, University of Southern Denmark, Odense, Denmark.|Sport Medicine Clinic, Orthopaedic Department, Hospital of Lillebaelt, Middelfart, Denmark.|Department of Psychology and Exercise Science, Murdoch University, Perth, Australia.
authors.forename: N
authors.initials: N
authors.lastname: Wedderkopp
authors.affiliation: Centre of Research in Childhood Health, Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.|Department of Sports Medicine, The Norwegian School of Sport Sciences, Oslo, Norway.
authors.forename: L B
authors.initials: LB
authors.lastname: Andersen
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D059352:Musculoskeletal Pain / Q000453:epidemiology*; D009141:Musculoskeletal System / Q000293:injuries*; D010806:Physical Education and Training / Q000706:statistics & numerical data*; D010809:Physical Fitness; D012574:Schools; D013177:Sports / Q000706:statistics & numerical data*; D014947:Wounds and Injuries / Q000453:epidemiology*
keywords: Epidemiology; elementary schools; multilevel modeling; primary schools