title: Cluster stability as a new method to assess changes in performance and its determinant factors over a season in young swimmers.
abstract: OBJECTIVE
  To apply a new method to identify, classify, and follow up young swimmers based on their performance and its determinant factors over a season and analyze the swimmers' stability over a competitive season with that method.
  
  
  METHODS
  Fifteen boys and 18 girls (11.8±0.7 y) part of a national talent-identification scheme were evaluated at 3 different moments of a competitive season. Performance (ie, official 100-m freestyle race time), arm span, chest perimeter, stroke length, swimming velocity, speed fluctuation, coefficient of active drag, propelling efficiency, and stroke index were selected as variables. Hierarchical and k-means cluster analysis were computed.
  
  
  RESULTS
  Data suggested a 3-cluster solution, splitting the swimmers according to their performance in all 3 moments. Cluster 1 was related to better performances (talented swimmers), cluster 2 to poor performances (nonproficient swimmers), and cluster 3 to average performance (proficient swimmers) in all moments. Stepwise discriminant analysis revealed that 100%, 94%, and 85% of original groups were correctly classified for the 1st, 2nd, and 3rd evaluation moments, respectively (0.11≤Λ≤0.80; 5.64≤χ2≤63.40; 0.001<P≤.68). Membership of clusters was moderately stable over the season (stability range 46.1-75% for the 2 clusters with most subjects).
  
  
  CONCLUSIONS
  Cluster stability is a feasible, comprehensive, and informative method to gain insight into changes in performance and its determinant factors in young swimmers. Talented swimmers were characterized by anthropometrics and kinematic features.
authors.affiliation: Dept of Sport Sciences, Polytechnic Institute of Braganca/CIDESD, Braganca, Portugal.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Morais
authors.forename: António J
authors.initials: AJ
authors.lastname: Silva
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Marinho
authors.forename: Ludovic
authors.initials: L
authors.lastname: Seifert
authors.forename: Tiago M
authors.initials: TM
authors.lastname: Barbosa
mesh_terms: D000886:Anthropometry; D054874:Athletic Performance / Q000145:classification* / Q000502:physiology*; D001696:Biomechanical Phenomena; D002648:Child; D016000:Cluster Analysis; D003163:Competitive Behavior / Q000502:physiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010809:Physical Fitness; D012621:Seasons; D013550:Swimming / Q000145:classification* / Q000502:physiology*