title: Comparing three underwater trajectories of the swimming start.
abstract: Once a swimmer enters the water they will not increase velocity, instead they will decelerate. One factor that will influence the velocity maintained during the underwater phase is the trajectory the swimmer adopts.
  
  
  OBJECTIVE
  Once a swimmer enters the water they will not increase velocity, instead they will decelerate. One factor that will influence the velocity maintained during the underwater phase is the trajectory the swimmer adopts. This study aimed to identify how different underwater trajectories affect start time in elite swimmers.
  
  
  METHODS
  Fourteen swimmers performed three dives: a shallow dive with little underwater time (Dive 1), a flatter dive with intermediate time underwater (Dive 2) and a deep dive with lengthy underwater time (Dive 3). The proprietary 'Wetplate' analysis system was used to collect performance time (time to 15 m) and other dive parameters.
  
  
  RESULTS
  A mixed modelling approach found Dive 1 was significantly slower than Dive 2 and 3 (time to 15 m). This indicated that both a shallow or deep dive slowed overall performance, with shallower dives adversely affecting performance the most.
  
  
  CONCLUSIONS
  On average, using a flatter trajectory with a maximum depth of -0.92 ± 0.16 m similar to Dive 2 may prove to be beneficial to start performance. More research is needed to examine the interaction between drag and depth for individual swimmers to better understand the mechanisms influencing these findings and to further explore the notion of an ideal underwater trajectory.
authors.affiliation: Aquatic Testing, Training and Research Unit, Australian Institute of Sport, Australia; Institute of Sport, Exercise and Active Living, College of Sport and Exercise Science, Victoria University, Australia. Electronic address: elaine.tor@ausport.gov.au.
authors.forename: Elaine
authors.initials: E
authors.lastname: Tor
authors.affiliation: Aquatic Testing, Training and Research Unit, Australian Institute of Sport, Australia.
authors.forename: David L
authors.initials: DL
authors.lastname: Pease
authors.affiliation: Institute of Sport, Exercise and Active Living, College of Sport and Exercise Science, Victoria University, Australia.
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Ball
mesh_terms: D000293:Adolescent; D054874:Athletic Performance / Q000502:physiology*; D001696:Biomechanical Phenomena; D003654:Deceleration; D004242:Diving / Q000502:physiology*; D005260:Female; D006801:Humans; D007101:Immersion; D008297:Male; D013550:Swimming / Q000502:physiology*; D013647:Task Performance and Analysis; D013997:Time Factors; D055815:Young Adult
keywords: Biomechanics; Depth; Dive; Swimmer; Trajectory