I wrote a recent article discussing the 3 most common mechanisms of ACL injury while skiing and how having that knowledge can possibly help to reduce the risk of ACL injury. There was great discussion following that article. People justly criticized the article for its lack of strong research to support claims made, and the unlikelihood one could deploy a “bail out” preventive strategy under voluntary control within fractions of a second preceding an ACL tear (it takes 200-500 milliseconds for an ACL to tear).
One NS member echoed the criticism and countered the article by mentioning that strengthening is his number one strategy for preventing ACL tears. And he’s right. There is an end of the ski season lost and found box amount of research that supports strengthening to prevent ACL injuries. In fact, symmetrical strength of the hamstrings/quadriceps, and proximal hip muscles is one of the five strongest predictors of primary and secondary ACL injury.
While I continue to subscribe to the first theory-skiers possess the processing time to recognize the sequence of events that will position them in a common mechanism of injury-I want to give equitability this week to strengthening as an awesome preventative strategy. I thought people would want to know what are the three effective and efficient strengthening exercises that theoretically correspond to the proposed three most common mechanisms of ACL injury. Here is my recommendation.
The first mechanism of injury is called the “slip catch” mechanism. This involves: 1) losing your balance going backwards, 2) the trunk rotating away from the center of body and towards the fall line, and 3) the downhill ski initially losing control but then abruptly catching an edge that puts the downhill knee into a position of internal rotation and valgus load that the ACL cannot handle. I would recommend the below exercise using the TRX RipCore:
https://www.newschoolers.com/videos/watch/967750/IMG-2635The second mechanism of injury is called the “landing back weighted” mechanism. This involves: 1) losing your balance going backwards in the air after a jump, 2) the tail of the ski touching the snow first, and 3) the boot pushing the shin forward and straining the ACL. I would recommend the below exercise using a strong mobilization band to perform what's called a "Spanish" style squat with a kettlebell:
https://www.newschoolers.com/videos/watch/967751/IMG-2766The third mechanism of injury is called the “dynamic snowplow” mechanism. This involves: 1) losing your balance going backwards during the initiation of a turn, 2) the outer ski loses control going outwards and 3) the inner ski as a result quickly transitions from the outside to it’s inside edge catching the snow abruptly and placing the knee into a similar position as the “slip catch” mechanism. I would recommend the below exercise using a kettlebell, floor slider and a strong mobilization band:
Try out these exercises and let me know what you think!
Dr. Benjamin Pierce Costa, PT, DPT
US Ski Team Rotational Physical Therapist