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Evaluating and developing the key determinants of push-start performance in bobsleigh

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posted on 2022-10-13, 13:21 authored by Robert Condliffe


It is a common belief in bobsleigh that  the  push-start  is  a  vital  aspect  of successful   performance.   Therefore, British   Bobsleigh   places   a   heavy emphasis  on  the  use  of  field-based  performance  testing  to  assist  with  both athlete monitoring and talent identification. There is a general lack of published academic literature in bobsleigh. Thus, limited evidence exists confirming the importance of the push-start, as well as validating the field-based performance tests  used  by  British  Bobsleigh. The  aim  of  this  thesis  was  to  validate  and develop the core principles and scientific underpinnings ofsquad monitoring and  talent  identification  specific  to  ‘brake-men’/’brake-women’  push-start performance in bobsleigh.Study  1  examined  the  relationship  between  the  push-start  and  finish  time across  elite  bobsleigh  competitions  for  2-man,  4-man  and  female event formats,  across  multiple  tracks  and over  multiple  on-ice  seasons. The  study demonstrated most tracks onthe elite bobsleigh circuit to beeither push-start dominant  or  moderately  influenced  by  the  push-start(common  variance  ≥ 10%). Thus,  it highlighted  the  value  of  evaluating  and  developing  push-start performance in British Bobsleigh athletes. Studies2  and  3 investigated  the  current  performance  testing  practices  of British  Bobsleigh,  used  in  both  talent  identification  and  squad  monitoring. Study  2  investigated the predictive  validity  of  the  ‘evaluation  test’  used  by British Bobsleigh to assess whether the whole test battery, as well as individual tests included within it relate to the bobsleigh push-start.Although this study confirmed the  predictive  validityof‘evaluation  test’  total  points  to  assess athletes  push-start  capabilities(r= -0.86  to -0.94),completion  of  the  entire testing  battery  proved  somewhat  unnecessary.This  largely  manifested  from the major finding of thisstudy that confirmed that the roll-bob push test could be used as a reliable (CV = 0.7 to 1.7%) and valid (r = 0.83 to 0.98) predictor of   push-start   performance.   Subsequent   attempts   to   explain   push-start performance  using  only  the  generalperformancetests  included  withinthe 

4‘evaluation test’, highlighted the importance of body mass and 30 m sprint time.However,  the  explained  variance  in  male  push-start  performance  (55%), highlighted a clear need to examine other performancequalities beyond those in the current British Bobsleigh ‘evaluation test’. Study 3 explored the reliability, discriminative validity and predictive validity of the British Bobsleigh ‘Keiser Squat  Test’.The  findings  of  the  study  confirmed  the  reliability  of  the  test protocol  (CV  =  6  to  10%),  as  well  as  reporting  very  large  to  near  perfect predictive ability for the female push-start (r= -0.86 to -0.96). Despite this, the strength of the  prediction  was only  moderate  in male athletes  (r = -0.30  to -0.47)and  the  test could  only  distinguish  betweenworld  class  performance (WCP)and national  development  (ND)male  athletes  at  a  moderate  load. Subsequently, other performance tests outside the current practices of British Bobsleigh  but  identified  from  the  winter  sliding  sport,  strength  and  power diagnostic and sprinting literature were explored.Study  4  investigated  the  validity  of  vertical  and  horizontal  jump test  metrics, completed under both bilateral and unilateral conditions, to predict push-start performance. The  majorfindings  werethat  horizontally  oriented  tests  (e.g. standing  long  jump  (SLJ))may  represent  better  push-start  predictive  ability than  vertically  oriented  tests  (e.g.  the countermovement  jump  (CMJ)and ‘Keiser Squat Test’). Also, maximising an athlete’s unilateral facilitation, as well as  minimising  any  between  limb  asymmetries  appears  to  be  beneficial  for push-start performance(r= 0.67 to 0.88). Thus, the addition of unilateral SLJ peak  horizontal  force,  bilateral  index  and  asymmetry  index  to  the  British Bobsleigh ‘evaluation test’, may help to account for some of the unexplained variance in push-start performanceidentified in study 2.Study  5  explored  the  discriminative  validity  and  predictive  validity  of  sprint force-velocity profiling for the bobsleigh push-start. Also, the study investigated the influence of a 16-week pre-season training phase on bobsleigh athlete’s sprint force-velocity mechanical profiles andassociated changes in push-start performance.  The  sprint  force-velocity  mechanical  variables Pmax,  relative Pmax, V0and Vopt wereall  shown  to  provide  discriminative  validity  for  the bobsleigh  push-start.  However,  of  these  variables, Pmax demonstrated  the strongest correlation with push-start performance (r= 0.80). At a group level, 

5the findings of the study detected training induced improvements in push-start performance,  sprint  speed  and Pmax(absolute  &  relative),  with  the  largest group-basedimprovements observed in absolute Pmax. This was reflected with all  athletes  making  worthwhile  gains  in Pmax,  however  this  did  not  always translate  to  improvementsin  push-start  performance  on  an  individual  level. Thus, theremay beother factors important for push-start performance beyond those measured in this study. To conclude, the push-start has a moderate to large influence on performance at most tracks on the elite bobsleigh circuit. The roll-bob push test provides a reliable and valid measure to quantify the push-start capabilities of bobsleigh athletes.  When considering the key underpinning determinants of push-start performance in bobsleigh, this thesis highlighted the importance of body mass, sprinting speed (30 m sprint time), sprinting maximal mechanical power (sprint force-velocity profiling), unilateral horizontal force production (unilateral SLJ) and power production under moderate external loads (‘Keiser Squat Test’). Thus,  practitioners  working  in  bobsleigh  should  consider  these  key  qualities when designing futuresquad monitoring and talent identificationperformance testing batteriesand designing training programmes



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