Reducing risk of injury on the other hand...
Injury prevention (read: 'injury risk reduction') is one of my favorite topics to discuss. I remember back in the good 'ol days when I first discovered the Functional Movement Screen and thought injury prevention was simply not scoring below a 14.
I've since realized it's not quite that simple...
Despite having A LOT more to learn and fully understand, my thoughts and approach to injury risk reduction has evolved since my early FMS days (I still use the FMS, but simply to determine if an athlete's joints can get into a position to train/compete/adapt to stress). It's human nature to want to intervene and make a [positive] difference, I just try to go about it in a different way now. (hint: I'm bias for doing something)
After listening to a recent podcast and reading a recent paper and blog post, I thought it would be a good idea to synthesize and share my thoughts (in combination with the thoughts and works of others much smarter than I!) when it comes to screening for risk of non-contact injuries. Let's get to it by first examining the screening process, then using a specific example of screening basketball athletes.
Sports Injury Prevention and Rehabilitation
One of the chapters in the book discusses the topic of the injury risk profiling process. This chapter comes after the medical pre-participation screening chapter (in the example below, we are assuming the athlete has already been cleared medically).
In the chapter, authors include two "injury risk equations:"
1) Predisposed individual + extrinsic risk factor = susceptible individual
2) Susceptible individual + injury mechanism = injury
*Definitions of the above (from the chapter) are as follows:
'Pre-disposed individual' is one who is more exposed to injury due to their own intrinsic risk profile (past injury, age, reduced joint ROM, muscle weakness, etc.).
'Extrinsic risk factors' include training/load regimen, weather, and the nature of the laws of the sport itself.
As far as 'injury mechanism' goes, I like to reference this post from PT Erik Meira, using force to understand injuries, as it isn't as simple as "OMG YOU LANDED WITH KNEE VALGUS I HOPE YOUR ACL ISN'T TORN."
*Erik also has an excellent post on knee valgus that goes along with the theme of this topic. He isn't paying me to promote his website, but he does put out some excellent content, so I don't mind sharing.
Basically, the point of sharing these equations right away are to:
1) Demonstrate there are other factors which can impact the likelihood of an injury
2) Nicely point out that the aim of screening is to impact the 'pre-disposed individual' category; to identify those athletes with increased risk of injury in order to intervene to reduce their increased risk.
Developing a Screening Tool
Here are the proposed steps from the chapter:
- Create a generic warning index (most common injuries in the sport of the athletes being tested)
- Individualize the warning index (non-modifiable risk factors, such as age, gender, previous injury, etc)
- Determine the risk factors (modifiable risk factors for the injuries identified in step one)
- Selection of appropriate assessments of injury susceptibility (tests used to identify risk factors)
- Assessment of movement proficiency (movement integration; examine system as an integrated whole)
- Dealing with the results (a screen is basically a 'filter' - what do you do with at risk athletes?)
- Review (Determining how often screening should be performed)
This makes sense, doesn't it?
Figure out which injuries are the most common in a particular sport --> which risk factors pre-dispose an athlete to these injuries --> figure out how to test for these risk factors --> determine if we can intervene to improve these risk factors --> then determine if improvement of these risk factors do in fact reduce risk of injury.
Let's put this process to use with a specific example...
Screening Basketball Players To Reduce Injury Risk
1) Generic Warning Index
2) Individualized Warning Index
For example, previously suffering an ACL injury is obviously non-modifiable, duh. What this step does though is filter athletes with previous ACL injuries into a bucket to make sure further testing is completed (hop testing, limb symmetry index > 90%, etc.). No, we can't change previous injury, but we can make sure the rehab after the injury was sufficient and complete!
Previous injury is basically the biggest 'filter' of non-modifiable factors in this category (Fulton, Brinkman, Heiderscheit, Smith, Paterno, Moradi, Freckleton)...but could we say being female increases risk of knee injury based on the literature (Smith, Hewett, Brophy, Murphy)? And what about age (Murphy)?
3) Risk Factors
Regardless, here are some of the 'risk factors' I came across in the literature:
1) Ankle ligament sprain - previous ankle sprain (Fulton, Brinkman), high BMI (Tyler), proprioceptive deficit (Riva, McGuine)
2) Knee pathology
I. Patellofemoral pain syndrome: training load/acute:chronic workload (Hulin), hip abduction strength (Rathleff), knee extensor strength (Crossley, Lankhorst), ankle doriflexion (Fong)
II. Patellar Tendinopathy: ankle dorsiflexion (Malliaras), acute:chronic workload (Hulin), knee extensor strength (Van der Worp)
III. Overuse: training history, acute:chronic workload (Hulin)
3) Low back pain: decreased lumbar flexion/extension and previous low back pain (Moradi)
4) Hamstring strain: eccentric hamstring strength/asymmetry (Opar, Bourine)
Now, my bias is toward doing something for screening rather than saying 'we don't have the evidence, etc', and therefore this bias may have lead to cherry picking some of the research listed above. As I mentioned before, it's difficult to tease out correlation/causation without prospective studies. I'm sure I missed a few studies, which is why I would love feedback on this list. And again, I reserve the right to change my opinion on this subject.
4) Test for Risk Factors
Based upon the risk factors described above, here are the potential tests to use to identify these risk factors:
Previous injury: questionnaire
BMI: body weight in kg divided by height in meters squared
Training load: acute:chronic workload
Ankle dorsi-flexion: closed kinetic chain dorsiflexion test, goniometer
Hip and quad strength: hand held dynomometer (nice blog here on testing), isokinetic dynomometer
Hamstring strength: Nordbord, Nordic hamstring field test
Neuro-muscular control: single leg squat, lateral step down test, landing error scoring system, Y-balance test, rolling???
Spinal range of motion: SFMA top tier multi-segmental flexion/extension
5) Assessment of Movement Proficiency
When it comes to assessing movement (most often bio-mechanical assessment), I'm not so sure there is such a thing as "faulty mechanics," which makes interpretation of these tests challenging (results from testing that are continuous vs. dichotomous).
As I mentioned before, I still use the FMS for determining if the joints of an athlete can get into a position to train and compete. I also like the Lower Quarter Y-Balance Test (YBT-LQ), which does have one prospective study examining injury risk. I'm interested in 3D MAPS, but haven't yet taken the course.
Assessing athletic qualities in single leg stance is also something I believe in. In rehabilitation, 'limb symmetry index' is often used prior to discharge (i.e. the scores of right leg testing must be at least 90% of the scores of the left). While I'm not so sure looking at single leg performance will predict injuries, I do believe significant asymmetries need to be identified and minimized to reduce injury risk (unless performance in a sport is enhanced by significant asymmetries).
Performance of single leg hop testing in the vertical, horizontal, and lateral directions appear to valuable. The triple hop may also be valuable as it has previously been a predictor of lower limb strength and power.
It may also be worth your time to synthesize the results from physical capacity testing (maximal strength, relative strength, rate of force development, core strength, agility, reaction time, energy system, sport specific testing, etc.) and use them to not only have a full picture of an athlete's presentation but to compare the results to other physical attributes of elite basketball players.
Preventing injuries is impossible. Sometimes, no matter how much training, screening, or monitoring is done, it just happens.
If the cost of an intervention is really low (strength training, pre-practice proprioceptive training, etc), why not simply incorporate this training for everyone regardless if an athlete passed the screening tests?
More prospective studies are needed to identify risk factors for certain injuries.
Reducing injury risk basically boils down to the human body's ability to absorb force. If the force from a jump, cut, etc. is greater than the capacity of a tissue (bones, ligaments, muscles) to handle said load, then injury occurs. So basically, we could say simply monitor load in athletes and we can reduce injuries. It's that 'simple.'
We shouldn't look at strength training as simply a means of getting big and strong. Thinking of strength training as a means to reduce injury risk is important!
("Your tissues are only as strong as the load placed upon them" - aka high levels of fitness/capacity are good!)
At the end of the day, you simply can't go wrong participating in a strength training program.
Looking forward to your feedback on this approach.