title: Shoulder and hip roll changes during 200-m front crawl swimming.
abstract: OBJECTIVE
  To determine accurately the magnitude and changes in shoulder roll (SR) and hip roll (HR) throughout a 200-m maximum front crawl swim and whether SR and HR were associated with swimming velocity (V). Bilateral roll asymmetries and timing differences between SR and HR were also investigated.
  
  
  METHODS
  Ten male swimmers of national/international level performed a maximum 200-m front crawl swim. Performance was recorded with four below- and two above-water synchronized cameras and four nonbreathing stroke cycles (SC) were analyzed (one for each 50 m). SR and HR were calculated separately.
  
  
  RESULTS
  Swimmers rolled their shoulders significantly more than their hips (P < 0.001). V generally decreased during the test, and HR was significantly higher in SC4 than in SC1 (P = 0.001). SR had a negative and significant correlation with V in each SC (-0.663 <or= r <or= -0.634, 0.037 <or= P <or= 0.049), with the exception of SC4. Although several roll profiles existed, left-side SR dominance was identified, with swimmers rolling their shoulders significantly more to the left than to the right side (0.000 <or= P <or= 0.022). Despite individual differences in the timings of maximum SR and HR to the left and right sides, no consistent pattern was found for the group.
  
  
  CONCLUSIONS
  Separate calculation is required for SR and HR to explore their influence on front crawl swimming. Faster swimmers tended to roll their shoulders less than slower swimmers. The increase in HR as the test progressed is possibly associated with a decrease in stroke frequency and increase in SC duration. Given that all swimmers were right-handed and that SR was significantly greater to the left than to the right side, it seems that factors related to handedness might affect SR symmetry in swimming.
authors.affiliation: School of Life Sciences, Napier University, Edinburgh, United Kingdom. S.Psycharakis@ napier.ac.uk
authors.forename: Stelios G
authors.initials: SG
authors.lastname: Psycharakis
authors.forename: Ross H
authors.initials: RH
authors.lastname: Sanders
mesh_terms: D000293:Adolescent; D001696:Biomechanical Phenomena; D002138:Calibration; D006615:Hip / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement; D015203:Reproducibility of Results; D012782:Shoulder / Q000502:physiology*; D013550:Swimming