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  4. Technical Note – Ballistic Measurement System – Defining Phases of the Countermovement Jump
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  4. Technical Note – Ballistic Measurement System – Defining Phases of the Countermovement Jump

PDF of this technical note is available here.

The Ballistic Measurement System Software Version 2021 can automatically locate the phases of a countermovement jump using criteria well established in the research literature (Krzyszkowski et al 2020). The three main phases are:

  • eccentric
    1. start = time at which force drops 2.5% below body weight
    2. end = time of zero crossing of velocity from negative to positive
  • concentric
    1. start = time of zero crossing of velocity from negative to positive
    2. end = time of takeoff defined as force dropping below threshold (default = 20N)
  • flight
    1. start = time of takeoff defined as force dropping below threshold (default = 20N)
    2. end = time of landing defined as force rising above threshold (default = 20N)

Sub-Phases of the Eccentric Phase

The eccentric phase is further defined within the BMS software using the criteria of (Krzyszkowski et al 2020). These phases are:

  • unloading
    1. start = time at which force drops 2.5% below body weight
    2. end = time of minimum force during eccentric phase
  • yielding
    1. start = time of minimum force during eccentric phase
    2. end = time of peak negative COM velocity (i.e. time of lowest velocity)
  • braking
    1. start= time of peak negative COM velocity (i.e. time of lowest velocity)
    2. end = time of zero crossing of velocity from negative to positive

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