Peak Velocity can be used to determine whether an olympic lift is missed due to bar height or technical error. However, you first have to understand what peak velocity is.
Peak velocity is a specific point in the movement at which velocity of the measured object (center of mass, barbell, projectile…) is at its highest. Depending on the type of movement being performed, peak velocity will occur at different regions within the movement.
Ballistic movements are those movements where there is no active deceleration phase. It is a movement that involves a ballistic action (throw, jump, toss, etc..) where the object you are moving (barbell, med ball, yourself, etc…) becomes a projectile.
During a jump, the human body becomes the projectile.
Non-Ballistic Movements
Non-ballistic movements have both an acceleration phase (speeding up) and a deceleration phase (slowing to a stop). Depending on the load and movement, these phases can change in length, but will always exist. Peak velocity in a non-ballistic movement tends to occur at the transition point between the deceleration and acceleration phases. For this reason, peak velocity in non-ballistic movements do not play a huge role. Unless you can measure the exact moment peak velocity occurs (which could tell you relative power during propulsive phase), mean velocity is a much more useful measurement for non-ballistic movements.
Ballistic Movements
Unlike a non-ballistic movement, peak velocity in a ballistic movement is an extremely important measure. If we are trying to determine how far something will move we need to know the exit velocity of the object (the speed of it when it is released). The exit velocity is normally the fastest part of the movement (you want to make sure what you are throwing is moving fast) and naturally this exit velocity will be peak velocity (fastest velocity of the movement). This means that if we know peak velocity of a movement (barbell jump, hang clean, baseball pitch etc…), we can determine how far the object will move.
**** This is only true if we make the assumption that angles of release are the same when comparing movements.
Olympic Movements
In olympic weightlifting, in order to complete a lift the bar has to reach a specific height and in order to reach this height the barbell has to have a specific exit velocity (peak velocity). As a coach, if you can measure peak velocity you can have a good idea as to whether or not the athlete missed the lift due to technical error (bar reached needed peak velocity and lift was not completed) or the bar not getting high enough (to low of a peak velocity for barbell to travel the needed height).
To determine what their peak velocity/bar height needs to be for a lift to be completed, the coach’s best bet would be to monitor peak velocities of the same movement at heavy loads. Eventually, through trial and error and data collection a minimal peak velocity threshold (MPVT) will be found. This MVPT would be the cutoff point can then be used to determine if a lift was missed due to technical errors or lack of bar height.
References
- Image 1: https://sites.google.com/site/thelongjumpproject/the-science-of-long-jumping
- Image 2:http://us.myprotein.com/thezone/training/benefits-of-olympic-lifting/