Despite the overwhelming prevalence of ACL injuries in athletes, ACL has become a taboo word for athletes and coaches alike in the fitness industry. So let’s start the conversation! Two questions every coach should be able to answer are:
- What is an ACL?
- What can be done to prevent ACL injuries?
Let’s start with the first question. ACL stands for anterior cruciate ligament. Broken down, ACL literally means front (anterior) cross-shaped (cruciate) tissue that connects bones (ligament), which is exactly what it is. The ACL is bodily connective tissue that connects the back of the thigh bone (femur) to the front of the primary shin bone (tibia). The ACL is one of the four major ligaments of the knee: ACL, PCL, MCL, and LCL. It is called cruciate, or cross-shaped, because the ACL and the PCL (posterior cruciate ligament) form a cross-shape together. The four ligaments of the knee work together to prevent excessive movement of the knee. The purpose of the ACL is to prevent the primary shin bone (tibia) from sliding too far forward. This basic anatomical information is a great tool to have in order to explain the ACL to clients that may be concerned about injuries in the gym, on the field, or in daily life.
Question 2 is not as straightforward. Due to the high prevalence of ACL injuries in sport, research has been continually evolving with recommendations over the past two decades. The good news is that the research-based recommendations on how to prevent ACL injuries is phenomenal in this day and age. The discussion of ACL injuries has evolved from being purely focused on rehabilitation, the surgical debate, and return to play protocols to now equally focusing on injury and reinjury prevention.
The big 5 components of ACL prevention that researchers seem to agree on are strength, plyometrics, agility, balance, and flexibility. The following exercises are not necessarily identical to ACL injury programs found in literature, but work to address the same big 5 components.
1. Hamstring Strength: Romanian Deadlift
The romanian deadlift is a weighted hip hinge with a minor knee bend that contracts and lengthens the hamstrings under an external load. If you are looking to improve your hamstring strength, this is an essential exercise.
So why the hamstrings? Humans are designed with three hamstring muscles, all three of which connect in some way to your primary shin bone (tibia) pulling it backwards to bend your knee (ignoring the hip right now). Remember when we were discussing ACL anatomy and I said the ACL helps prevent the shin bone from sliding too far forward? Hamstring muscles and your ACL share a responsibility when it comes to primary shin bone movement. The overarching theory is that strengthening the hamstrings can help support the ACL.
2. Neuromuscular Training: Foam Roller Glute Bridges
One of my favorite neuromuscular training exercises is a foam roller glute bridge. To perform this exercise, place your heels on the foam roller while laying down with the knees bent. Brace the glutes and hamstrings for the instability of the foam roller (to prevent it from rolling during the motion), and lift the hips off the ground in a single, controlled motion. There are many variations to this exercise. Two of my favorites are single-leg bridges (only placing one heel on the foam roller with the other off the ground) and long bridges (placing the heels farther away from the butt to increase hamstring lengthening). Single-leg adds core muscle recruitment. Most importantly though, the rolling capacity of the foam roller forces muscles to continually make corrections during the movement to help better train your neuromuscular system. As a bonus, this exercise is also a great hamstring strengthening exercise.
3. Plyometrics: Skater Hop to Stick
Most coaches have seen a typical skater hop drill before where an athlete rapidly bounds laterally back and forth between feet to work on explosive power in a non-traditional direction. However, adding a stick to a skater hop drill is what upgrades this plyometric drill to one of my favorite ACL injury prevention exercises. To add a stick, to a skater hop exercise, choose one side to focus on. Have the athlete perform half of a traditional skater hop, but on this designated side add an isometric pause for 5 seconds. You will be surprised at how many athletes exhibit poor balance or biomechanics during this sudden isometric in a rather explosive drill. Be sure to address any biomechanic flaws, particularly proper glute activation and ankle/toe/knee/hip alignment. Athletes may not naturally track their knees in a perfectly centered position though, so do not be shy about technique correction. Knee collapse (or genu valgum) has been coined in research as a predicting factor of ACL injuries and is therefore a great and necessary component of an ACL injury prevention program.
4. Agility: W-Drill
The W-Drill is a drill that I have used with college level athletes for return to play protocols with lower body injuries. It is one of my favorites because it incorporates nearly every type of typical movement seen on a court or field in addition to several different changes of direction. All you need to complete this drill are 5 cones or designated markers. Set them up in a W formation pictured below in the diagram. Have the athlete start at marker 1. The athlete will sprint to marker 2, shuffle to marker 3, change direction, but continue shuffling to marker 4, back pedal to 5, and then turn and sprint back to 1. As always be sure to check if the athlete has proper form and technique, and correct accordingly.
5. Balance: Single-Leg RDL
Single-leg stability is essential in all ACL injury prevention programs. A single-leg RDL is a single-leg hip hinge where the leg off the ground is extended in a straight line backwards while the torso folds forwards. Signs of a good single-leg RDL are a straight back, no loss of balance, and a straight extending leg with hips aimed toward the ground. If this exercise becomes easy for your athlete, add perturbations, an unstable surface like a bosu ball, or take away vision. These are all great ways to progress your athlete and make the balance challenge even more difficult.
I hope you were able to learn from this article. I am a huge advocate for injury prevention programs and interweaving them into typical strength and conditioning programs–particularly for common injuries like ACL sprains. These are 5 of my essential exercises when it comes to ACL injury prevention, and they are all rooted in research. Please feel free to borrow and share these ideas because this is knowledge that as a community we want to spread as wide as possible. Good luck!
- Huang Y. Jung J. Mulligan C. et al. A Majority of Anterior Cruciate Ligament Injuries Can Be Prevented by Injury Prevention Programs: A Systematic Review of Randomized COntrolled Trials and Cluster-Randomized Controlled Trials With Meta-analysis. American Journal of Sports Medicine. 2020;47(6):1505-1515.
- Johnson J. Capin J. et al. A Secondary Injury Prevention Program May Decrease Contralateral Anterior Cruciate Ligament Injuries in Female Athletes: 2-Year Injury Rates in the ACL-SPORTS Randomized Controlled Trial. Journal of Orthopaedic & Sports Physical Therapy. 2020;50(9):523-530.
- Lang P. Sugimoto D. Micheli J. Prevention, treatment, and rehabilitation of anterior cruciate ligament injuries in children. Journal of Sports Medicine. 2020;1(1):133+.
- Padua D. DiStefano L. et al. National Athletic Trainers’ Association Position Statement: Prevention of Anterior Cruciate Ligament Injury. Journal of Athletic Training. 2018;53(1):5-19.
- 5. Marx R. Mykleburst G. The ACL Solution: Prevention and Recovery for Sports’ Most Devastating Knee Injury. Demos Health; 2012.