During physical activities, the time available to produce a force is infinitely shorter than the time required to reach maximal muscle capacity.
Previous studies have observed that the time elapsed between ground contact and ACL rupture is on average 50-60 ms, suggesting that this is the time window available for any attempt at dynamic stabilization of the joint through muscle contraction.
Sports movements include ballistic movements, defined as very fast movements whose objective is to accelerate a moving mass as much as possible so that it reaches a high speed in a very short time. This is the case for vertical jumps, running and most movements performed in physical and sporting activities.
Thus; (1) isokinetic tests do not allow a rigorous analysis of the components related to the speed of the movement; (2) functional tests such as jumping, which only give a distance between one leg and the other, do not allow the calculation of precise and reproducible variables concerning the force and speed of the movement, in particular during the first milliseconds of the movement, and do not provide information on compensation phenomena. It is therefore interesting to use the ballistic tests developed to monitor the movements of athletes as a new possible indicator of the return to sport.
The main objective of this study is to evaluate the performance of ballistic tests in predicting failure to return to physical activity 24 months after ACL surgery.