What is the true magnitude of the ACL injury problem in sports today?
It is a significant global issue. The 2023 FIFA Women’s World Cup has really illuminated this, with a host of big names that won’t feature in the tournament due to ACL injury. Also, ACL injuries in the English Women’s Super League and the US NCAA football have never been more prevalent.
However, Australia is leading the world with ACL injuries. Based on estimations, the annual number of ACL injuries in Australia is expected to more than double by 2030-2031 compared to 2017-2018 levels, with a projected cost being estimated at a staggering AU$300M. Sadly, our AFLW competition statistically leads the world when compared to other team sports. The ACL injury rate in the AFLW competition is 3–7 times higher when compared to other female team sports and 10–19 times higher when compared to male team sports, such as European handball and football (soccer).
How can we shift the focus from curing ACL injuries to preventing them in the first place?
Sometimes we have significant barriers to interventions with serious and complex medical conditions. In these situations, there is understandably extensive research required, ethics committees, financial resourcing, trials, etc. When it comes to ACL prevention, there are no real barriers to intervention. The only apparent barriers are knowledge (coaching), compliance, and allocation of time. At times many leading experts around the world have suggested there exists a culture of acceptance of ACL injury as being something that ‘happens’ to women.
In contrast to anatomic risk factors, power, strength, and neuromuscular coordination deficits can be addressed with proven interventional strategies. These interventional strategies do not require expensive equipment and/or facilities. A lot can be said for good quality coaching, the appropriate time to implement, and the time for the athlete to adapt.
Which sports have successfully addressed and reduced the disparity between male and female ACL injury rates?
There are many examples of other sports around the world, such as skiing, dancing, and some women’s rugby programs that have put in place proven methods to significantly mitigate ACLs. World renown expert, Bill Knowles originally built a reputation over 20 years ago when he was at the Burke Mountain Ski Academy. Bill reduced ACL injuries with mogul skiers from approximately 30+ per year down to 2-3 per year. The Australian Women’s Rugby 7s program has an excellent track record with ACL injury over the past 7 years with only 2 ACLs (1 contact & 1 non-contact). The program was led by respective S&C coaches Craig Twentyman in the Rio Olympics and Tom Carter in Tokyo Olympics. Both these coaches did a superb job providing these athletes with advanced, but appropriate leg power development and coordination training modalities. There are other examples of physical development programs in the US that have resulted in an 88% drop in ACL injuries. This should be the rule – not the exception. We all accept the ‘non-modifiable’ factors associated with female ACL injury. However, infinitely more can be done with modifiable factors such as total body coordination and strength.
What are the contributing factors that make AFLW (Australian Football League Women’s) rates of ACL injuries particularly high?
The issues facing the AFLW athlete are not unique. The same issues will be faced by NRLW athletes this year and are also being reported by field and court sports in Europe and North America. There has been an explosion of female athlete participation in our field sports in particular, which is great. However, for various reasons, our female athletes have not had the background, or been afforded the same opportunities as our male athletes. The covid lockdown period has and will have implications for us. Our children are not as physically active as they used to be. Furthermore, early specialisation with single sports is depriving our developing athletes of the broader movement vocabulary they require. Particularly, body awareness and control with locomotive skills, which field and court sports demand such as running, jumping and landing, etc. These generic skills are the foundation for being able to express sports skills.
If a sport does have a distorted number of ACL injuries, then it is obvious these athletes are not adequately prepared for the demands of the game. As such, preparation is either inadequate or inappropriate. The question is how?
The subject of the quality and quantity of coaching and support staff for female field and court sports is something that is discussed globally. The argument of financial resources is typically raised, but conversely so is the duty of care. Some would suggest it becomes false economy to take shortcuts here. Particularly when you take into account the cost of surgery and rehabilitation (~AU$15K per athlete) and replacing players. Also factorising, of course, the long-term issues of not regaining pre-injury levels of performance and early onset of osteoarthritis. However, there are many fine examples around the world of women’s programs being resourced appropriately.
How does the Prepare to Play (P2P) Triple Hop Test help in assessing ACL injury risk?
Prepare to Play has partnered with VueMotion in designing the P2P Triple Hop Test, which has been specifically designed to assess both locomotive performance and related coordination; the lack of which, is correlated to ACL injuries. In comparison to expensive and time-consuming laboratory-based testing methods, it offers a much more functional, economical, and readily available method for field or court sports at all levels. The test utilises AI technology that analyses an athlete’s movements. This approach offers an unprecedented, prospective, and preventive approach to field or court sports preparation. The test can be completed with minimal equipment and on any firm and level surface, ideally in an athlete’s own training environment. An analysis is made available as an individual athlete and a group report within 24 hours. From there, interpretation and recommendations can be made available, which provides valuable insights for practitioners and coaches from a coaching and programming standpoint. The uniqueness of the test is that it is able to assess performance and injury risk synonymously.
The test also offers a paradigm shift, in that, we no longer need to be ‘chained’ to one-dimensional movement analysis via in-situ laboratory-based testing equipment such as force plates or jump mats. We can now seamlessly analyse training modalities organically but with lab conditions.
The test is also advantageous for those athletes wanting to rehabilitate from injury, as effectively as possible. Given that bounding and hopping are respectively exaggerated and unilateral forms of running, the triple hop test shows a clear relationship to gait analysis. Given ACLs are predominantly a running-based mechanism, we must relate the restoration of function to running.
The test has also been validated by Australian Catholic University (ACU) against the Vicon camera-based motion system in a laboratory setting, showing a 95% accuracy. It is not the intention to try and compete with systems like Vicon. The P2P Triple Hop Test is a coaching tool. The intention is to make it readily available to more people – more often.
There has been a good deal of interest and uptake from Australian clubs and national bodies. Namely, A-League teams, Queensland Rugby League, NRL, Melbourne Storm, and a leading football club from the Netherlands.
What are the key gaps or limitations in the current research on ACL injury prevention?
We should never stop researching or looking for gaps within our research. However, we have a plethora of research. In fact, there is now 6 times the research relating to ACLs in comparison to 20 years ago. A quick search on PubMed will reveal this. A lack of research isn’t our issue, but simply the utilisation of it. The narrative and statistics regarding ACLs haven’t changed in 30 years – in fact, it’s getting worse as we know. We must remember that the transfer of sports science/medical research into practice must require a coach. The whole point of sports science is to challenge, change and improve coaching practice – not research for the sake of it. Although, at times there can be a reductionist approach to the research, in there is an exclusive focus on the stance leg and in particular the knee in isolation. It requires strength and coordination of the entire body to ensure forces are absorbed in other parts of the body rather than the knee per se.
Many of the answers are staring at us in plain sight. Go and watch any world-class coach of vertical and horizontal jump events. The techniques and methods these coaches teach axiomatically offer substantial insights into preventive measures for ACLs associated with high-speed stepping.
In what ways can coaching practices be improved to better address ACL injury prevention?
Quite often we have a false dichotomy of injury prevention and performance enhancement. These two important aspects of athlete preparation are absolutely synonymous. What is required athletically and technically for ‘stepping’ and ‘stopping’ in terms of performance enhancement also has a protective benefit. Research clearly shows it is eccentric rate of force (RFD) development that distinguishes elite v sub-elite athletes in the speed and power events. Eccentric RFD also separates Men and Women as the effect of gravity takes effect. However, eccentric RFD is the most important quality for the prevention of impact injuries – particularly in women.
The primary training modality to improve this quality is plyometrics, which as we know, develops the important quality of reactive strength. Often there is an unfounded perception that plyometrics as a modality causes injury; conversely, it prevents injuries. This perception has resulted in quite a lot of conservatism with the programming and coaching of this training modality – particularly with the female athlete. It could be suggested that the fear that plyometrics can cause injury may well result in many field and court sport athletes being undertrained in terms of preparing them for their respective sports. We must remember that when we change direction, we must tolerate forces up ≥4.5 times body weight. Or, depending on how fast we run at speed, up to >6 times body weight. As such, we need to apply the training principle of progressive overload to ensure our athletes can tolerate and negotiate these forces. Ask an experienced S&C coach how many injuries have resulted from when they have coached plyometrics as a modality over the years. I think you will find you will draw a blank.
Importantly, we shouldn’t just think that the development of reactive strength is only relevant to the lower body; it is a total body quality. Mainly as the trunk/core has a significant role to play in force reception and production. This is not to suggest that traditional strength training doesn’t have a role with field and court sport athletes – it does. Although, as Vern Gambetta has always said, “if the only thing you do is weightlifting, then all you end up with is weightlifters”.
There are some differences between female and male athletes, which require consideration when designing strength training programs. Essentially females should undertake the same strength training methods as males. However, we need to consider the following generalisations with the female athlete:
- Compared to males, females are approximately 50% and 30% weaker in upper body and lower body strength respectively
- Females lose strength and muscle tone faster than males
Due to these challenges, as well as structural and hormonal considerations, strength training is even more important for female athletes than male athletes. As such, some training variables and training principles require consideration:
- More frequent exposure to strength within a training week
- For strength training to be periodised through all phases of the training year. This is a requirement for the female athlete – not an option
It is worth noting that, the female athlete is typically ready to commence formal strength training at a younger age in comparison to the male. If we consider the years when the female athlete is most vulnerable to ACL injury (late teens-early 20s), then it makes sense to commence training interventions post-puberty with females from age 13-16 years. These are the critical years to formally commence coordination with jumping, landing, and foundational strength.
What role does strength and conditioning training play in ACL injury prevention?
I suggest it’s critical our S&C coaches have a well-developed coaching skill set and knowledge in developing running, jumping, and landing skills. Also, to consider a move away from the mindset of just having quantitative performance measures and shift to physical mastery with our younger field and court sport athletes. For example, not having a sole emphasis on how much can be lifted; or how fast can they run. Namely, a more qualitative approach to how the athlete runs, lifts, jumps, and lands. Importantly, mastery of these skills. Quantitative performance can then be appropriately pursued at the elite level.
Jack McLean is the founder of Prepare Like a Pro. He loves coaching people so that they can reach their personal/professional goals and become the best that they can possibly be. He is currently the Strength & Rehab Coach of Melbourne Football Club and has worked as Strength & Conditioning Coach at Hawthorn Football Club. Jack is a Level 3 Australian Strength & Conditioning Association and Professional Coach and a Level 1 Australian Weightlifting Federation Coach.