Jerk is acceleration/time, which makes the units of jerk distance / time to the 3rd (Distance/time/time/time)
Jerk = acceleration/time
Jerk is the rate of acceleration over a given period of time. High levels of jerk essentially cause the “jerking” motion one might feel when someone slams on the brakes of car (fast deceleration over a short period of time) or the same feeling of being pressed back against a seat when someone slams on the gas (assuming your car has a rapid rate of acceleration).
In sporting movements, an athlete who can express a high amount of jerk might be deemed “twitchy”. Those “twitchy” athletes are able to stop and go (accelerate) over short periods of time. For example, an athlete doesn’t necessarily need to be extremely fast to create space to get open in football, basketball or soccer, but they need to have high rates of acceleration over short periods of time.
Change of direction work can be indicator of Jerk. Rarely do get close to top speed in such movements. However, acceleration and rate of acceleration is critical
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High levels of jerk can also play a large role in injury. When it comes to contact injuries (breaking bones, ligament sprains/tears, muscle strains/tears) a lot of it is caused by the fact that the joints, muscles and tendons are rapidly accelerated over a short enough period of time (Jerk). The high level of jerk means the body cannot act fast enough to brace the soft tissues, joints, and bones.
Learning how to produce and absorb high levels of jerk can possibly improve performance and reduce the likelihood of non-contact injuries.
Image 1: https://blogs.longwood.edu/aclinjuries/