Strength and Plyometric Training for Athletes at Higher Risk of ACL Injury

Go ahead and raise your hand if you want to reduce the chance of a non-contact ACL injury? Hopefully you did or at least in your head you did and if you actually raised your hand, that's cool too. If you “raised your hand” you should actively be doing 3 things. Last year I wrote a blog on Neuromuscular Coordination Training for Athletes at Higher Risk of ACL Injury, where I mentioned 3 training techniques I use for reducing the chance of an ACL injury in athletes. Also in that blog post I went through the general anatomy and aspects of the ACL so this time around I will save the boredom and jump right into it. The 3 training techniques I use are neuromuscular coordination, strength and plyometrics. 

Strength Training

When it comes to preventing non-contact ACL injuries, I cannot exaggerate enough the importance of being strong. I think the term strong gets thrown out of context quite a bit, especially in the soccer world. Being strong does not mean you have to be bulky or thick. I say this because there is no other sport in the world that thinks more poorly of strength training. The soccer world believes that lifting a semi-heavy weight will make you grow an insane amount of muscle and then in return, somehow that muscle will not let you move, which will then hinder on the pitch performance. I can tell you that is wrong. Yes, if an athlete performs exercises with certain volumes and intensities an athlete can add unwanted mass, but that just shows how incredibly important it is to have a good performance coach. I personally use relative strength as an indicator of adequate individual strength because it incorporates an athletes body weight. So basically, an athlete doesn’t need to deadlift 400 pounds in order to be considered strong, but instead they should aim to perform single leg exercises with moderate to high weight. I like single leg exercises because it doesn’t necessarily allow an athlete to go considerably heavy (in their head) when in reality it's functionally better and heavier. For lifts such as the trap bar deadlift and squats I look for 1.5x their body weight as an estimate of “they are strong enough” for more intense training.  

Now, it's important to know that not every exercise for every muscle group will directly help in increasing strength to aid in a reduced chance of a non-contact ACL injury. I focus on increasing strength in the core and the leg muscles. I pay special attention to the core (traverse abdominis, internal and external obliques, rectus abdominis) hip external rotators (piriformis, gluteus maximus, quadratus femoris), hip abductors (gluteus medius and minimus, tensor fasciae latae (TFL)), vastus medialis obliquus (VMO) and hamstrings (biceps femoris, semitendinosus and semimembranosus). The muscles of the posterior chain are important for many reasons, but even more for soccer players, due to the high demand of the quads during the game of soccer. Sports create imbalances. Quad dominant athletes need to spend more time strengthening muscles like the hamstrings and glutes to even out the imbalances that soccer creates. Strength training without addressing imbalances is subpar. 

So what type of exercises should these athletes focus on? Because it is important for these types of athletes to decelerate properly (slow down) majority of what I utilize are quasi-isometrics and eccentrics. Quasi-isometrics and eccentrics play a vital role in developing adequate deceleration patterns which allow an athlete to absorb force properly. Of course, quality of movement has to be the focal point of any exercise or it doesn’t really matter what an athlete does. Quasi-isometric and eccentrics do a great job of not only increasing strength but also improving overall quality of movement. As a strength coach, I have to see a certain level of strength before progressing in exercises, especially onto high level plyometrics and change of direction drills. For me, lower body movements and exercises have to specifically focus on the external rotators, abductors, VMO and hamstrings to have any prevention effect on the ACL. Strength training also allows an athlete to develop resistance to fatigue, which makes it even more important because there is a higher chance of an ACL injury occurring when an athlete is in a fatigued state. 

Fire Hydrant with Band

Physio Hamstring Curls (2-Concentric/1-Eccentric)

Plyometric Training

The effectiveness of plyometrics is undeniable. It’s important that certain plyometrics are not introduced too early as they are not all created equal. Plyometrics have shown to improve lower body stability, dynamic balance, proprioception, technique and overall biomechanics -- to name a few. This is exactly what we want to achieve in athletes that are at a greater chance of having an ACL injury. The bases of plyometrics is that they will decrease the sensitivity of Golgi tendon organs (GTOs) (your “protector”) against high tension loads in the muscle allowing the elastic components of muscles to undergo a greater stretch. Plyometrics create changes in the stretch-shortening cycle (SSC). Because of this, it will allow an increase in performance of the muscle spindles which will always improve proprioception and motor coordination (Alikhani et al., 2019). All in all, plyometrics will increase neuromuscular adaptability including the rate at which muscles can be recruited. 

The faster an athlete can recruit the production of force from a muscle the better off they will be. Just like muscles can produce force, they can also absorb force. I would argue that absorbing force (decelerating) plays just as an important role as raw speed in most sports. I get athletes in all the time that have not been trained correctly to slow down. You would think that playing basketball, soccer, football etc.. that an athlete of such would know how to change direction and properly accelerate and reach max speed, but nope. In order to train correct braking, landing, deceleration and absorption of force an athlete needs to be able to be comfortable in positions in which they are flexed at the hip, knee and ankle. I like using a variety of deceleration techniques/drills and drop landings to help develop proper deceleration patterns such as, lower body stability, dynamic balance and proprioception.

1-Leg Drop Landing

Once I have done an efficient job on coaching the athlete to absorb force I then start to introduce more intense plyometric drills. By progressing plyometrics, an athlete will develop better lower body kinematics along with hip stability. It's important to progress, as introducing different variables of movement need to be added in order for an athlete to gain motor control, coordination and dynamic stability. This would be considered adding a new stimulus (like the example below). The key in order to keep progressing is for an athlete to show proper completion of basic braking exercises with proper biomechanics. 

1-Leg Vertical Jump with Push Assist

Here are 2 training techniques as well as neuromuscular coordination I consider to be “musts” in order to reduce the chance of having an ACL injury. If you are under the “High Risk” category go and find a good sports performance coach who can help you stay injury free. I will finish by saying that the only poor outlook that strength and conditioning should receive is if it is done incorrectly. When in doubt, just get strong! 

References
Alikhani, R., Shahrjerdi, S., Golpaigany, M., & Kazemi, M. (2019). The effect of a six-week plyometric training on dynamic balance and knee proprioception in female badminton players. The Journal of the Canadian Chiropractic Association, 63(3), 144–153.