We’ve all seen this scene in pro soccer, only to see the player get up and resume playing just as soon as he sees he didn’t manage to get the ref to pull out a yellow card. Cue eyes rolling.
But jokes aside, players are not always crying wolf. ACL injuries really are quite common in soccer and many other sports that involve cutting and changing direction.
ACL injuries are quite burdensome and pretty much universally dreaded by athletes and individuals involved in sports. These injuries may require a long lay-off from sport and at times, may be career-ending.
The idea of ACL injury prevention, then, becomes quite interesting for athletes, therapists, trainers and coaches alike.
Injury prevention is a term that not everyone likes. It is a term that is meant to refer to implementing structure and strategies that reduce injury risk, occurrence and severity.
But what actually goes into an injury prevention program?
An exercise-based prevention program for ACL injuries must address risk factors and include neuromuscular training strategies.
Since most ACL injuries occur via non-contact mechanisms, such as during landing and deceleration, there is a coordination component of the lower limb that needs to be included in an effective injury prevention program.
An ACL injury is not simply the result of an isolated joint or muscle strength issue. Nor should we treat it so.
Let’s discuss the elements that need to be included in an exercise-based prevention program for ACL injuries.
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ACL INJURIES – RISK FACTORS
Let’s start by identifying what it is exactly that we can work on to build a prevention program for ACL injuries.
Numerous risk factors for ACL injury have been established in the literature, so much so that a consensus statement was put forth by the International Olympic Committee (1). This consensus statement highlights that ACL risk factors are multifactorial and identifies 4 distinct areas of risk factors: external, internal, hormonal, and biomechanical.
The objective of injury prevention is identifying and intervening on ACL injury risk factors that are trainable and modifiable.
External risk factors such as footwear, equipment, playing surface, may or may not directly influence the risk of non-contact ACL injury and are not really modifiable.
For example, when working with a skier, we cannot change the fact that they wear a ski boot. That said, there is research out there regarding “ACL-friendly” ski bindings.
Internal risk factors refer to anatomical factors related to individual structure or gender differences. For example, the Q-angle, femoral notch and ACL size have long been studied to understand the higher incidence of ACL injuries in females vs males (2). There is no real consensus on how they influence ACL injury risk, and again, these factors are not modifiable.
Hormonal risk factors are related to increased knee laxity during the ovulatory phase, which again are non-modifiable.
On the other hand, biomechanical risk factors are certainly modifiable and trainable, as these include not only technique, such as that for landing and cutting, but also neuromuscular factors.
Neuromuscular factors include elements like motor control, strength, and muscle activation and recruitment patterns
All things training. Exactly what we LOVE to do, am I right?
Let’s use some practical examples to build structure around that.
THE KNEE IN THE KINETIC CHAIN
The common mechanism of injury for non-contact ACL injuries appears to be deceleration, which occurs when the athlete pivots, changes direction, or lands from a jump. Because the knee is part of the kinetic chain and is an intermediate joint, it will be impacted by what goes on at the ankle and the hip.
This is why prevention programs for the ACL as well as for the entire lower extremity, are largely based on landing and deceleration progressions. We are looking to train the athlete’s capacity to optimally absorb, distribute and transfer forces along the lower extremity.
Fundamentally, joint range of motion is certainly an important factor. In women, higher joint laxity may increase the potential for excessive dynamic knee valgus.
Certainly, the opposite is not desirable either. Too much joint stiffness may impact the hip joint’s capacity to absorb ground reaction forces. It may also impact its ability to absorb the forces of trunk and pelvis rotation.
I discuss the impact of hip mobility on ACL risk factors in this article, so make sure to read that. Here is a great exercise to increase hip internal rotation in the MOBILIZATION sequence:
Whenever I work on Mobilization, I typically program for a total of 2 minutes, so either 1 set of 2 minutes or 2 sets of 1 minute depending on the exercise.
Distally, ankle mobility is also important as the first point of contact for absorption. There is also an article on that topic specifically on the blog.
THE HIP AS A CENTRAL PIVOT
Whenever we increase range of motion, one important thing we need to do to follow-up on that is to work on dissociation. In order to actually have a joint, each component of the joint must be able to move independently of the other.
In deceleration or change of direction, the hip joint serves as a central pivot for the body
Not only is the hip absorbing forces from the ground up, but it must also absorb rotation of the trunk and pelvis.
In order to do this effectively (and essentially for the hip to be a hip) the femur must be capable of moving independently from the pelvis and the pelvis must be capable of moving independently from the femur.
Dissociation exercises can be selected to work either. Airplanes are great for pelvis on femur dissociation:
You could also use the same set-up, but for femur on pelvis dissociation:
Here I like to use 2 to 3 sets and do either 12-15 reps or work for 20-30 seconds.
Of course, we also want to able to create stability though that hip as it acts as a central pivot. This is why you would also want to include anti-rotation exercises along with your dissociation exercises in your Activation sequence.
This half-kneeling banded dowel hold works amazing to create rotation torque through the hips:
Since this is an isometric hold, I use 2 to 3 sets of 20-30s.
NEUROMUSCULAR TRAINING TO PREVENT ACL INJURIES
There is ample evidence to show that neuromuscular training helps prevent ACL injuries (3, 4).
Hubscher et al. found that: “multi-intervention training programs including a combination of mobility, balance, strength, plyometric and sport-specific exercises were effective in reducing the risk of lower limb injuries by 39%, the risk of acute knee injuries by 54%, and the risk of ankle sprain injuries by 50%”.
While range of motion, motor control and strength are definitely important elements of a prevention program for ACL injuries, we also need to work on neuromuscular factors like muscle recruitment patterns.
We do this for two very important reasons:
- Because tissues and structures that have not been subjected to stress levels similar to those encountered during the specific sport are at greater risk of injury (or reinjury)
- The more the pattern is repeated, the more advanced information and preparatory activity is available for the neuromuscular system to control fast movement
Not only is this paramount for injury prevention, it also improves neuromuscular efficiency, and as such, performance.
But what does this mean from a practical perspective?
It means that after we have spent time improving range of motion, motor control and strength, we are now ASSOCIATING the movement along the kinetic chain.
We are now working on HOW the lower limb absorbs, transfers and distributes those torsional forces of deceleration, landing and change of direction.
While we want to progress towards sport-specific movements in this Integration sequence, you can start with movements focused on deceleration and even exaggerate the deceleration requirements as a way to increase capacity.
This side shuffle with rotation exercise is a great example of decelerating the torso rotating on the hips:
With these deceleration drills, I would typically use 3 to 5 sets of anywhere between 6-10 reps. You could use a light weighted bar or a medicine ball – something that will create a momentum to accelerate the torso rotation.
And you could follow-up with a landing drill like a single-leg landing:
EXERCISE-BASED INJURY PREVENTION – WHEN?
An exercise-based prevention program for ACL injuries must address risk factors and include neuromuscular training strategies.
There is ample evidence to show that injury prevention CAN work – whether it DOES work requires a delivery strategy.
The sequence I have outlined in this article can be used as a warm-up. This will ensure that you get the buy-in and repetition to make it work.
Here’s what it looks like with the sample exercises I showed in the article:
Naturally, this would need to be periodized to progress to more and more sport-specific drills.
Of course, these are sample exercises, and I never want you to confuse your exercises with your practice. So, to recap, the elements that go into a prevention program are:
-provide the athlete/client with the appropriate range of motion so they can properly absorb and distribute forces along the kinetic chain
-provide them with motor control and awareness using dissociation and anti-rotation exercises
-improve how forces are absorbed and distributed in a definitive sequence of deceleration of segments
The truth is, we can prevent ACL injuries. We can reduce injury risk, occurrence and severity by implementing a strategy to make what we know CAN work actually work. (Unless the player is just trying to get a yellow card…)
REFERENCES
- Griffin, L. Y., Albohm, M. J., Arendt, E. A., Bahr, R., Beynnon, B. D., Demaio, M., Dick, R. W., Engebretsen, L., Garrett, W. E., Jr, Hannafin, J. A., Hewett, T. E., Huston, L. J., Ireland, M. L., Johnson, R. J., Lephart, S., Mandelbaum, B. R., Mann, B. J., Marks, P. H., Marshall, S. W., Myklebust, G., … Yu, B. (2006). Understanding and preventing noncontact anterior cruciate ligament injuries: a review of the Hunt Valley II meeting, January 2005. The American journal of sports medicine, 34(9), 1512–1532. https://doi.org/10.1177/0363546506286866
- The female ACL: Why is it more prone to injury?. (2016). Journal of orthopaedics, 13(2), A1–A4. https://doi.org/10.1016/S0972-978X(16)00023-4
- Herman, K., Barton, C., Malliaras, P., & Morrissey, D. (2012). The effectiveness of neuromuscular warm-up strategies, that require no additional equipment, for preventing lower limb injuries during sports participation: a systematic review. BMC medicine, 10, 75. https://doi.org/10.1186/1741-7015-10-75
- Hewett, T. E., Lindenfeld, T. N., Riccobene, J. V., & Noyes, F. R. (1999). The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study. The American journal of sports medicine, 27(6), 699–706. https://doi.org/10.1177/03635465990270060301
- Hübscher, M., Zech, A., Pfeifer, K., Hänsel, F., Vogt, L., & Banzer, W. (2010). Neuromuscular training for sports injury prevention: a systematic review. Medicine and science in sports and exercise, 42(3), 413–421. https://doi.org/10.1249/MSS.0b013e3181b88d37
Mai-Linh Dovan M.SC., CAT(C)
Certified Athletic Therapist
Founder of Rehab-U
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