Approximately 1 in every 3000 people experience an anterior cruciate ligament (ACL) injury, with women being roughly 3 times more likely than men to suffer. It is also more common in contact ball sports, those who are less fit and have not adequately trained for the demands of their sport. Half to two-thirds of ACL injuries require surgery (ligament reconstruction), with the recommended minimum recovery time often being 9 months before you can fully return to sport. A typical ligament graft takes up to 2 years to fully heal, even with an adequate rehab programme. Furthermore, 30% of patients have a second ACL tear within 24 months of returning to sport, 21% suffer an ACL tear to the other leg and 9% tear the reconstructed ligament in the same time frame. If you are someone who doesn’t require surgery for your ACL injury, you will still need extensive physiotherapy and importantly, rehabilitation, to recover effectively. It’s also important to recognise that around 50% of ACL tears also involve damage to other tissues in the knee.
Needless to say, ACL tears, while not the most common sporting injury, are considered one of the more severe and traumatic to experience. A lot of emphasis and information you find online talks about recovery times, rehabilitation methods and surgical methods (type of graft). However, as a Strength & Conditioning Coach, my job is to think “how do I help prevent my athlete getting injured in the first place?”. While it impossible to completely remove the occurrence of ACL tears, particularly where contact is involved, recent research has shown that appropriate strength and conditioning programmes can reduce injury rates by roughly 50% (67% in females). If more people thought proactively about reducing ACL injury risk and acted accordingly, many would save the need to reactively treat and rehab from long-term injury.
So, what are the biggest risk factors associated with ACL tears in non-contact situations and how can we train to help reduce those risks, both from a technique standpoint as well as a strength training standpoint.
To design a training programme, we first must understand what actually increases the risk of the injury in the first place. ACL injuries have been studied in depth over the years – let’s firstly tackle the movement/technique-related factors, which include:
- Wide foot plant positions
- Excessive hip abduction
- Externally rotated foot positions (relative to the knee)
- Trunk sway (lateral flexion & rotation) on the same side as the planting leg
- Excessive knee extension upon ground contact
All of these have been associated with increased rotational knee stress, which is one of the primary mechanisms involved in causing the ligament to tear/rupture when forces exceed the tissue tolerance.
Other factors that are more physicality-focussed (i.e. your ability to tolerate the loads), are things that are unavoidable during intense sports performance, and so, involve simply developing a tolerance to. These include:
- High velocities of movement (fast actions)
- Very high ground contact forces (more force going through a single leg)
- Large angles of cut (sharper turns)
The technique-associated factors are most easily coached and improved through technical drills, where body position and change of direction technique is altered. The physicality-focussed factors are things that will not change with technique, and are best addressed by improving physical qualities such as strength.
With an awareness of the primary risk factors, what exactly can we do to reduce such risk?
When it comes to technical improvements, change of direction drills and plyometrics are your best friend. After all, you have to practice a skill to get better at it, and efficient change of direction is certainly a trainable skill. I won’t go into specific drills, but as a coach you should be deciding on the drill that best suits your athlete(s) based on the demands of their sport, skill level, and the specific changes you want to make.
But let’s look at some general cues that can be given to help improve the technical factors associated with ACL injury. The art of providing effective cues is to use simple cues that encourage the desired movement pattern without requiring the athlete to overthink the movement, as this slows them down and negatively impacts performance. So the basic cues I recommend starting with are:
- Use a ‘forward-facing’ neutral foot position
- Bend at the knee and hip when turning
- Lean the direction you want to go
These will directly reduce foot rotation and lower centre of gravity, which should in turn require narrower foot plants and less hip abduction (killing two birds with one stone) and also reduce trunk sway. This means imply focusing on one or two things that address a large number of risk factors.
So the next step is, how do we incorporate or progress these cues in a training block?
Whether it’s change of direction drills or plyometric exercises, the key is to start with simple, single-action tasks and progress to drills/exercises with multiple actions and less predictable environments. For plyometric exercises, this could be starting with low amplitude pogos, moving onto jumps, then bounds and then hops. And within those, you could move from vertical, to horizontal, to lateral and finally rotational exercises. This allows for progression of the skill in a simple task before increasing complexity once competent.
For change of direction drills, I would start with single-action (following a similar progression to the plyometrics in terms of direction), predetermined change of direction drills. This could then progress to multi-action drills, before incorporating some semi-chaotic (predetermined action but awaiting a cue to perform it) and then moving to completely unplanned drills (such as reacting to random cues and small sided games).
Whichever drills you prefer to use, allowing time and repetition to build competency with the desired technique in a simple task before progressing them is the best way to help ensure that the desired technique remains as the complexity of the drill increases. In fact, some technical skills can even be incorporated into warm ups to help save time and avoid taking time away from other training variables.
As previously mentioned, the physical demands associated with ACL injuries such as increased movement velocities, greater ground contact forces and greater angles of cut cannot be avoided if performance outputs are to be kept high. Therefore, alongside the technical changes, we must improve an athlete’s ability to tolerate the physical demands.
A lot of emphasis is placed on acceleration, however, in order to change direction we must first slow ourselves down, and the faster we are running the harder that is. Furthermore, the longer it takes us to slow down, the more likely we are to be beaten by an opponent, highlighting the need to be able to slow down very quickly and in as few steps as possible. Because high forces are a risk factor in themselves, using the penultimate step or two before the change of direction to decelerate can help reduce the risk of injury on the planting foot. This requires a lot of eccentric strength (braking strength). Therefore, improving eccentric strength is my first port of call.
This can be done using plyometric and resistance exercises where the eccentric phase is overloaded, such as drop landings, depth jumps, or flywheel training. It can also be done using deceleration drills. Eccentric strength training does have the potential to lead to more soreness and muscle damage than concentric training, so care must be taken with the volume prescription of these exercises. Starting with smaller drops, lighter loads and slower velocities is a good idea, and then gradually increasing these variables providing their technical proficiency remains as desired.
Another factor which cannot be forgotten, is the fact that when we run and change direction, it is often a single leg that is working at a time, meaning a lot of force goes through each leg. In a game, you don’t always have a choice of which leg is the plant leg, so making sure both legs can handle the loads is important. Single leg strength is essential for effective change of direction.
Another thing to consider, is that changes of direction don’t happen in a single plane of motion, but multiple. Because of this, including lateral and rotational exercises is wise for ensuring they are strong and competent in the planes of motion they will be exposed to in games.
The final major strength focus I consider is core strength, as excessive lateral flexion and trunk sway also increase ACL injury risk. Incorporating anti-lateral flexion and anti-rotation strength exercises alongside dynamic flexion and rotation exercises can help ensure the core is capable of handling the forces involved and optimum posture is maintained.
When selecting exercises it is crucial to choose those that incorporate a combination of eccentric strength, single leg work, lateral/rotation planes of motion and anti-flexion/rotation core strength. Some exercises will incorporate all of these in one, while others should be more isolated to correct specific areas of weakness. Similar to the technical drills, start simple with exercises that focus on a single variable, then progress to exercises that incorporate multiple if appropriate, but bear in mind that more complexity does not necessarily mean more effectiveness, so don’t complicate exercises for the sake of it because they look fancy.
The best injury reduction programme is an effective strength and conditioning program. I would suggest designing a performance focussed program that simply incorporates some of the factors mentioned today, such as change of direction and deceleration drills in field-based training, progressive plyometrics and strength training that still focuses on strength development, but simply incorporates eccentric, single-leg, and exercises in varying planes of motion. You don’t need a separate ‘ACL risk reduction program’ to effectively reduce the risk of injury, providing your strength and conditioning training is purposeful and thought through.
At Pyramid Performance & Health, we specialise in providing performance training and rehabilitation. Whether you’re looking to reduce injury risk as discussed in this article, or you’re looking for guidance with a rehabilitation programme, please get in touch via the contact page for more information – we’d love to work with you.
Written by Tom Whitaker, S&C Coach at Pyramid Performance & Health