Episode 240 | A Hidden Factor in ACL Strength Testing – Familiarization

What is up team? And welcome back to another episode on the ACL Athlete Podcast. Today, we are talking about strength testing, specifically familiarization (that’s a long word) of strength testing. I think this is an important topic to touch on. This is something that came up recently as I was talking with the team. We were working through some different athletes and their test results, and just comparing from one test to another test and trying to align that with also what we’re seeing with what they’re doing in the gym dynamically, to just correlate all the information and see, okay, does this all make sense?

One thing that was interesting and that we see very consistently is that athletes, when they go to get a strength test done. Let’s say, for example, that they’re actually getting tested legitimately, whether that is through a dynamometer or through an isokinetic machine, being able to actually get isolated quad strength testing or hamstring strength testing. That is what we are talking about specifically here. 

This concept will apply honestly to anything that is being tested or any performance-based measure for the athlete. But specifically, I want to talk about strength testing because one: it’s important. Number two is that there’s so much that matters with the process of testing.  We’re just going to assume that the athlete is being tested appropriately. 

The one thing that is interesting is that there is a familiarization process with getting tested. I just want you to think about this for a second. You’ve had an ACL injury and likely an ACL reconstruction, maybe not, or maybe a different type of procedure. But with that said, the majority are going to have an ACL reconstruction, so you have either an allograft or an autograft, and then comes a time where you’re going to get strength tested. 

Now, let’s just use, for example, the three-month mark, a very common timeframe. You’re far enough out from the surgery that you will get strength tested. It’s not too early that you might flare things up by kicking too hard. And let’s just take, for example, the quad strength test, where you’re just kicking into an immovable object, isometric testing to be able to see how much force your quad can produce, or how much torque it can produce. We get an objective number, we get a data point, something that gives us a value for what that force stands for. 

When athletes first get tested, and I see this all the time with athletes, I’m testing here, whether it’s athletes we see are getting tested by other people we know. We refer them to other places for our remote athletes. This is something that is very common. And what happens is that when this athlete is getting tested. One, leading up to the testing, it’s important to communicate about this and understand that this is not a make-or-break or a pass-fail type situation, especially at the three-month mark. We know that the quads are going to be weaker than the other side. Therefore, this is not something that we’re going to surprise ourselves and be like, 90% symmetry, and where you should be at nine months now.

No, we know it’s going to be weak. We just want to assess and see how weak we are compared to the other side, or what the difference is. Therefore, communicating about this test, also not making it such a big deal of this test as a pass-fail, but more so, of saying it’s a data point. It’s for us to collect information, for us to continue to be more and more targeted with our exercise prescription, our program design, to make this more tailored to you. Because otherwise, we’re flying blind. If you don’t test, you are guessing in this process, and so this is something that we want to make sure we can get an objective measure on.

With testing the narrative leading up to it is really important not to make it a big deal, but then also to let them know, we’re going to look at some numbers. With some of my athletes, I don’t even tell them. They’re used to using the device in an endurance way or strength-building way, but we are not “testing.” And that might be to just remove the anxiety and just to see as time goes on, leading up to the three-month mark.

But let’s say we are doing the thing, we are going to a strength test, and that’s what’s going to happen. They get put into the position, the setup. Typically, they have an ankle strap on. I’m thinking more of an isometric strength test with a dynamometer here. They’re sitting on some type of box, or maybe it’s a knee extension machine with a device hooked up to it to be able to measure the load or the force being pulled out, just like basically what a weight scale does or a crane scale does. That’s essentially the same thing. That’s what a dynamometer is. This athlete is getting set up, and we want to get this value. There’s this whole process of setting up, educating, being able to let them warm up, and understanding their status coming into it. Are they dealing with pain? Are they dealing with swelling? Are they dealing with any soreness from sessions before? Did they move a lot that day? We want to collect information to understand the context in which this testing is going to take place. 

The other thing that is really key with this is that the setup is going to be really important to be consistent in the queuing. This is going to be something that if I say kick out as hard as you can versus kick out as fast as you can, surprisingly, you’re actually gonna kick out a little differently because you’re going to jerk that machine or the setup if you go as fast. But if you kick out as hard, it might be a little different. The queuing matters a lot. The buildup to it matters a lot. There’s a familiarization with this process. I think this is something that really flies under the radar, but massively impacts your testing results during ACL rehab.

And so here, for example, if there are athletes here in Atlanta, there’s a hospital system that will do strength testing on an isokinetic machine at three, six, and nine months, which is awesome. Therefore, they will get their results at the three-month mark. And the thing that is not often communicated to them is basically the results of what we’re seeing and also how to interpret that. But then also, for us to take this as a data point, it’s helpful, but also the familiarization of these tests matters so much more than we give it credit. And the example I want to use here is imagine stepping into a gym for the first time and someone tells you to test your max strength on a new machine you have never used before. We could say it’s a leg press. We could say it’s a hack squat machine. It could be a knee extension machine. And some of these are maybe a little bit more straightforward, but it’s your first time stepping into the gym. And if someone asks you to do a max strength test, odds are you’re not going to give it a true reflection of your capabilities. It’s not just because you’re weak, but because you just don’t know how to use the machine yet. And that same principle applies to ACL rehab testing here. The important thing is that there is a learning effect with this process that we need to make sure we understand as we interpret and analyze the results of these different tests.

Familiarization is the process of getting used to a test, the movement, the setup, even the environment, the queuing, the communication of it, and the duration of it. When an athlete does a knee extension strength test, for example. Using the isokinetic or handheld dynamometer, their first test is rarely their best. And while you might say, yeah, well, we’ll do multiple repetitions. Sure, but that doesn’t change that specific moment. And the thing is that the first test is often a reflection of their uncertainty or unfamiliarity rather than their actual quad strength.

The thing that’s always interesting in this is that sometimes the athletes will get strength tested. Let’s say it’s an isometric device that they have access to regularly. Then four weeks later, their numbers really jump up because then they can get familiar with it, and they’re, oh, I’ve done this before. If you’ve done a machine at the gym before, then you’re going to be okay. I know what my parameters are. I know the feel of it. A lot of this is such a feel in this process, but not to mention the apprehension that also gets missed. This is hard. You have just had major reconstructive surgery on the knee. The last thing you want to do is kick out as hard as you can into something when you’ve been dealing with pain, swelling, all these limitations over the past few months. Your knee has basically been really challenging to work with, and all of a sudden, they’re asking you to do a maximum output of as hard as you can, kicking out.

And while that might feel okay. In reality, mentally, what’s going on. Even though we know that the knee won’t snap, some people who are thinking their knees might snap by kicking out as hard as they can, especially when you think about this ACL that is healing. My knee is still “fragile.” It’s pretty normal. And therefore, you might even hold off on kicking out as hard as you can to feel things out. I think this is really important to share with you guys because sometimes you’ll get these test results from your physical therapist or whoever’s testing this, and be like, well, yeah, I’m pretty weak. This is really bad. Or the interpretation of the results doesn’t truly reflect your abilities. And what we often find is that it doesn’t necessarily align with where the athlete is and what other things they can do. Being able to take the stairs down, being able to single-leg squat down, being able to get their knee into a good positive shin angle, and knee over their toe. And then we’re just well, this doesn’t add up because this test is showing this, but they’re able to do all these things, or vice versa. The test overestimated how much this athlete could do because the setup was bad; therefore, they couldn’t do any of those things, but the strength test overestimated it.

But today, really from a familiarization standpoint, usually what happens here is that it’s often underestimated due to that unfamiliarity with the device and with the test itself. Think about the same thing with a jump test. A lot of athletes have never been told to do a counter movement jump with their hands on their hips, or they haven’t been told to do a drop vertical jump, where they drop down and then they hit the ground as quickly as they can. They jump up and land, right? That is not something that we are normally just doing in our everyday lives, and you usually aren’t doing that unless you are being tested from a performance standpoint with a gym, with a very specific group and setting. Otherwise, it would be more based on a rehab process like ACL rehab, if they’re testing those things. But it’s just going to take time because you have to get used to it, like anything else, a new skill, a new movement, and especially after an injury like this. 

The thing that happens with this is that the test-retest reliability improves, especially after you have more sessions with it. I see this very, very consistently when I see my athletes; they are so used to being strapped up to the dynamometer because we’re not always strength testing. I might be indirectly, without them knowing it, but I embed these things within the sessions. And we might do endurance sets, for example, where they do long hold, repeat isometrics, and we might test the waters a little bit depending on the day, how I’m feeling, how they’re feeling, what I’m seeing, and the timing of everything. This is something that if they’ve done it enough, you’re okay. They can almost sit back and not even think about it, and just really push and make sure that they are so used to this that we cannot fault familiarization as a problem with the results. This is the learning effect that we are looking at: people just get better at the test just by doing it more. But it’s not just because they’re necessarily getting stronger. So that’s super important here. 

The other thing that I touched on briefly was just setup inconsistencies. This is something that is a challenge because it is not very easy for people to just consistently set this thing up. It just depends on the clinic, the setting, what this looks like, who is setting it up, and their education. But we’re talking about seat position, the strap tightness, talk about joint angles. Is it at the proper angle? That’s typically one of the things that we see. Is everything stabilized? We want to reduce noise. This is something that can really skew results, especially if the athlete is tested by just different people with a similar device, if you will, but the setup is a little different, or the queuing is different. We’re not necessarily comparing apples to apples as apples to oranges because the queuing, the setup, and the angle are all different, even though we are testing knee extension strength. So that is one thing that I do want to add as a caveat here. 

I’ve had a recent situation like this where one athlete was being tested somewhere else, and they were able to lift their entire bodies up off the table. If you guys know, you can’t do that with this quad knee extension test because that’s basically pulling in your whole body. And of course, you’re going to output more strength. The thing is, we got to keep it rigid, locked down, and it needed to be isolated only to the knee. Therefore, they need to make sure it’s only coming from the knee versus their bodies lifting off the table, the box, whatever it is. This athlete had a crazy overestimation of the testing results. And I was this doesn’t really add up to how she looks and how she’s feeling and performing. And then I tested it, and there was a 30%, 40% difference. We had to have a conversation about this in terms of where the inconsistencies lie. But that is something, again, more so can underestimate, but also overestimate. I did want to add that little caveat since we’re talking about testing, getting familiar, and analyzing the results of this. 

Why does this matter? Of course, reinjury rates are at an all-time high. We know that return to sport rates are also at an all-time low. We need to make sure that we are making decisions based on good data and information. Limb symmetry index is something that we are going to be using, targeting certain criteria, like 70% to 80% for return to running. And then also getting 90%, 95% and beyond for returning to performance in sport. We want to make sure that we are comparing the legs appropriately, making sure that they’re not under-tested due to that inexperience. It can be something that maybe we also overestimate their readiness. So that is something that is going to be important, especially from a symmetry standpoint, because if they’re not used to the test, then they may just have a lower output. And then from there, if you’re using symmetry alone, you might have two tires that are half flat or half full that you are comparing them to. So that’s going to be an important factor within this. 

This is something that I have just been putting a lot of thought into in terms of talking with our team, talking with our athletes, to just make sure we don’t overlook this one concept. And especially for someone like myself, going through my own rehab and having tested recently. There was one test that I did that I was oh, I wasn’t super familiar with doing personally myself. Over time, as I have done these tests, I’ve gotten more familiar. My output has improved. I have also gotten stronger. Yes, but it’s interesting to see this reference to my other leg as well. And the familiarization played a big role in that. 

The biggest thing here is to let the athletes get familiar. Let’s do serial testing, where this could be every four to six weeks, even more frequently than that, based on time availability. It doesn’t have to be a full max effort test. It could be just getting the athlete used to doing it. and then also making sure that we have consistent setup protocols and making sure the queuing and everything, all the conditions are replicated as similar as possible. Letting them know that this is not their final test. The first test, especially, people usually improve over time. Testing is a skill. It’s not just an assessment. 

This is something that I hope is helpful for y’all, especially if you’re an ACLer listening to this a all right I did a test at month three, and it just didn’t hit where you wanted it to. Take that for what it is. That’s information for us. But then also, if you’ve never done that before, reference back to the gym example. If you walked into the gym, never done anything, and someone asked you to do a max bench press, how do you think you’re going to do? You’re probably not going to exert as hard as you can. You might end up keeping a little bit in the tank to protect yourself because it’s new, and then you’re also going to get better over time. But the caveat here is that, let’s say you also had a chest injury that you’re healing from, or a shoulder injury, that’s going to make you a little bit more hesitant if that’s your first time.

That’s something that I hope is helpful for you guys as you’re going through this process. If you have any questions, let me know. Otherwise, I will catch you next week on the next episode. This is your host, Ravi Patel, signing off.