title: Longitudinal changes in young people's short-term power output.
abstract: OBJECTIVE
  The influences of age, body size, skin-fold thickness, gender, and maturation on the short-term power output of young people were examined using multilevel modelling.
  
  
  METHODS
  Subjects were 97 boys and 100 girls, aged 12.2 +/- 0.4 yr at the onset of the study. Sexual maturity was classified according to Tanner's indices of pubic hair. Peak power (PP) and mean power (MP) were determined on two occasions 1 yr apart using the Wingate Anaerobic Test (WAnT). The data were analyzed using multilevel regression modelling.
  
  
  RESULTS
  Initial models identified body mass and stature as significant explanatory variables with an additional positive effect of age, which was smaller for girls' MP. A significant gender difference was apparent for both power indices with girls achieving lower values than boys. A significant incremental effect of later maturity (stages 4 and 5 for pubic hair development) was identified for MP only. Subsequent incorporation of sum of two skin-fold thicknesses into the model yielded significant negative parameter estimates for PP and MP and negated both the stature effects and the maturation influence upon MP.
  
  
  CONCLUSIONS
  There are gender differences in the longitudinal growth of performance on the WanT. Regardless of gender differences, body mass and skin-fold thicknesses appear to be the best anthropometric predictors of WAnT determined PP and MP in young people.
authors.affiliation: Children's Health and Exercise Research Centre, University of Exeter, United Kingdom. N.Armstrong@exeter.ac.uk
authors.forename: N
authors.initials: N
authors.lastname: Armstrong
authors.forename: J R
authors.initials: JR
authors.lastname: Welsman
authors.forename: C A
authors.initials: CA
authors.lastname: Williams
authors.forename: B J
authors.initials: BJ
authors.lastname: Kirby
mesh_terms: D015992:Body Mass Index; D002648:Child; D002657:Child Development; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008954:Models, Biological; D010809:Physical Fitness; D011627:Puberty; D012737:Sex Factors