Episode 247 | 7 Key Considerations for Strength Testing in ACL Rehab

What’s up guys? Welcome back to another episode on the ACL Athlete Podcast. Today, we are talking about something that often gets overlooked, but plays a massive role in decision-making throughout the ACL rehab process, and that is [drum roll] strength testing. Do I talk about strength testing too much on here? It’s possible. But I think it’s important because it’s an important part of the process. And more specifically today, I want to walk you through seven important considerations when strength testing ACLers; whether you’re using isokinetic dynamometer, handheld dynamometer, or even a force plates setup, maybe it’s a knee extension, five-repetition maximum. This isn’t just for strength testing, if you will, it’s for assessments for testing. You could take a lot of this stuff and apply it across a lot of assessments that you may do in this process, and some may apply more to a knee extension-based test. 

But with that said, I just want to cover some important considerations on this and knowing that these aren’t the only ones. But ones that I want to talk about for today because I think it can provide some insight for you, whether you are an ACLer, whether you’re a clinician coach, whatever domain that you’re in within this ACL rehab world, it can apply to you. For a lot of you, too, it can help with some perception of maybe the, some of the results or some of the tests that you get, or maybe the lack thereof. Because one of the things that we find is that a lot of ACLers in general are not being tested, or they’re not being tested appropriately. Because sometimes we’ll hear people say, yeah, I got tested, I got an MMT, or pushed into someone’s hand, or they did just a hop test, and that was it to be cleared for sport. Or they did a single-leg squat to a box, and that was their strength test. 

Different things can be stated as testing, but we want to make sure we’re testing the right things. We want to make sure that we are looking at peak strength, we’re looking at power, we’re looking at range of motion, we’re looking at the way someone can dynamically move, the way that they can also isolate certain movements and strength test those compound-based movements. There are a lot of different criteria within this, depending on where athletes are, that we are going to be assessing to make sure that they are physically prepared and also mentally prepared, especially for the demands of what they’re trying to get back to. We want you to be very prepared for this, and that is where tests allow us to know. 

When you get in a car, whenever that dashboard has no lights on it, you can basically know that the KPIs have been met, that this car is doing just fine. There are no problems with it. Of course, things can happen, but with that said, usually that light on the dashboard comes on first. And that’s usually something to tell us, oh, we need to get it further assessed. But there’s a test done, a diagnostic, in order to inform, like, okay, what do we need to improve or what do we need to change in order to clear this to make sure the car is safe to work again. The same thing here in a sense, and that’s where testing comes into play. 

Now let’s get into it. I’m going to go through this list. I’m going to be short and sweet with this stuff because I want you to get to the point. I also don’t want this to be a long episode for you because no one’s got enough time these days. So let’s keep it short and sweet, Ravi.

Number one, don’t put too much stock in the first test. There is a learning curve to testing, especially whenever there’s high output demanded or it’s a newer movement. And then let’s also not forget just the psychological component of this. We want to be mindful of this first test. Especially in early in ACL rehab, you might be eight to 10 weeks post-op, and you might be doing some isometric, submaximal testing, if you will. You’re not hitting max efforts at that point. You may be, but usually at 12 weeks, let’s just say cleanly three-month mark. Some people are going to be doing some assessments in max strength testing, and there might be some people who aren’t ready for it yet. But with that said, when it’s the first time, especially someone’s first ACL process, first time really doing these max outputs, they’re still learning how to produce force again, how to kick that thing out, how to trust that knee. There might be hesitation with pushing hard, getting used to it,  or just the anxiety of being tested itself. Everyone has test anxiety to some degree, some more than others. And that first session, think of it as a baseline for behavior as much as it is for performance, so don’t put too much stock in it.

Number two, perform serial testing. What does serial testing mean? We are going to consistently test this thing over a period of time. It happens in a series, if you will, and then testing once tells you very little, especially every three months. There are certain times where certain equipment, like isokinetic dynamometers, the access to it is every three months. For example, here, there is a group that does it every three months when you go see your surgeon. I think that’s fine, right? That gives us a baseline and a good proxy. If I had my perfect world, could we do it every six to eight weeks? Awesome. But those machines are very few around. And then also it’s just not the way that the current system, especially for a bigger system like this is set up. But with that said, can we do the test more frequently to give us data to be able to be a little bit more targeted? Absolutely. So that’s why testing periodically will not be as helpful versus testing consistently. We like to say every four to six weeks, we will be conducting an assessment. This gives us a trajectory. It gives us a very short-term roadmap, if you will, to the longer roadmap. But it also allows us to make sure that we are staying very intentional and not wasting time. It helps us get the athlete comfortable with the test itself, and also helps you to see if the programming is trending in the right direction.

This also removes pressure when you know the test is not like a one-shot deal, like a pass or fail or return to sport. They’re more likely to give authentic effort every single time this is done. I think there’s a lot of value in this, and I think this can help just remove that anxiety of testing. Therefore, people know what this looks like, know how it feels. Of course, this can be adjusted. But most importantly, it allows us to target exactly what direction we need to go to and be more surgical in our approach to our programming, the way we adjust things. There are times where we might test something while we have a good idea. The athlete might surprise us, one way or another. It might be way worse than it is, or it might be much better. We could just be like, cool, we have hit this checkpoint or this bucket, now we can actually prioritize our focus on something else versus waiting another six weeks, eight weeks with the same exercises or maybe just progressions of those when they’ve already tackled what we need to from it. I think serial testing helps us to just expose any of those gaps that we have, but then also just be more efficient with timing and know are we going in the right direction? It’s making sure the ship is not going off course by any degree; it’s going in the right direction very consistently and keeps you informed. Keeps the game plan informed. 

Number three, sometimes the strength test is a tolerance test. What I mean by this is that if the ACLer is experiencing pain, you are not testing their true strength; you’re testing their pain tolerance. Pain becomes the limiter for how much torque they can produce, or how much force strength that they can produce for that particular movement or that muscle. If we’re doing a knee extension test, the front of the knee is bugging you. Maybe you irritated it right before, or maybe it’s just hurting during because you’re doing a max test. You had a patellar tendon, you had a quad tendon, and you had a complicated knee surgery. You’re still early post-op. You did a bunch of stupid stuff right before that. The knee is just not in a healthy state where it’s like it can give a full go at this without it talking. It ends up being more of a pain tolerance test, and that pain becomes more of the limiter. It’s still helpful, valuable data, if you will, because it gives us an objective way to track what the pain is and what the strength output with that pain is over time. 

Let’s say, for example, you have 4/10 pain. Let’s just give it a ballpark number. During the test, you produced an output on the device of 30 kilograms. That’s how much force you can produce. But let’s say the next session, you may even have the same amount of discomfort, but you produce 40 kilograms. Therefore, that allows us to know you can tolerate and produce more force at the same amount of pain. Or, later on, you might decrease that pain and be able to have the same force output, if not higher. These are tolerance tests to give us an idea of, okay, how is this athlete looking? 

And a lot of times, especially early in the process, or if someone may be going through a flare-up or a setback. It’s a tolerance test versus thinking this strength test is your pure output. You got to factor in, if you’re dealing with pain. You’re going to be limited to some degree because the body is going to put a little bit of a brake. Imagine you’re in your car and you put a little bit of that emergency brake on, even if it’s 20%-30% of that emergency brake, you’re going to have that pulled up while you’re hitting the gas pedal. Are you going to be able to go as fast as you could in that car? No. That’s what pain is doing whenever we are trying to kick out as hard as we can, so just know it could be a tolerance test. 

The padding, if we’re talking about a knee extension test, the padding matters a lot. I’ll see a lot of setups where people, their back of their knee is digging into the box or whatever they’re set up on. I will see that they have a strap that’s about an inch thick that is around their ankle when they’re kicking out for an isometric test. And I’m like, do the test to yourself. I promise you, it is not going to feel good. And I’ve done this to myself. There are times where I always ask my athlete, I’m like, are you comfortable? Do you feel anything digging into you? And at this point, I’ve perfected my setup here. But the thing is, if you feel any discomfort, as silly as it is, because sometimes you’re like, oh, it doesn’t matter. I’m kicking on as hard as I can. Exactly. If you are kicking out as hard as you can, the only thing you want to make sure of is that the pad and everything is comfortable and it’s not cutting into their leg. Because you’ll just get false results. People will subconsciously hold back to avoid that discomfort. Make sure that the setup is comfortable, make sure the pad has a good surface area. The strap that you’re using is soft enough for them to push into it without having pain or discomfort. Super key result because I’ve seen people when we change that setup, they can output 10%, 205, 30% more, depending on the setup and how much that was holding them back.

Number five, the only thing that should be moving is their knee, and that is when I’m talking about a knee extension test and knee flexion test. When we are testing isolated strength on the knee, usually when we’re talking about here, the quads or the hamstrings, which are obviously number one and number two, the importance of this whole process. We need to make sure the only thing moving is the knee. ACLers want that number to go up, I promise you, they will do everything in their power to lean back, twist, lift their hips, anything to get that number to go up. Keep the system rigid. I want you to think about, can you lock this person in as much as possible with proper queuing, proper straps? Usually, at least there’s a strap around the thigh whenever there’s true max testing. But the knee joints should be the only thing moving, so you’re actually measuring knee extension strength and not some type of also full body compensation in it. The biggest thing that I see with knee extension and setups is that when people get set up, they will be in that box. They will have the ankle cuff on them. They’ll kick out. As they start kicking out, their hips will start coming off the ground. That’s something that we want to make sure we avoid. You can strap their thighs down with a seatbelt strap, a lashing strap. You can have them hold the side of the box that they’re on. You could have their back up against a rig. There are a bunch of different ways for us to make sure that they don’t compensate in order to just make sure it’s just the knee. 

The thing that has been interesting is just seeing other clinicians’ set up, people asking me for feedback. But then also just looking at, because we have a lot of ACLers who get tested other places, and we ask for the setup or we ask about it, and it’s very different. Sometimes the data on that is challenging because there are other parts moving like there is a group here where they test and they allow their athletes to lean fully back while they get tested. I promise you that is not a standard way, that’s not how we do it in the research, and they’re going to throw their hips into it. It’s just really challenging whenever there’s not a standard practice across this. In general, the rule is, can we just keep the knee as the only thing moving? In this case, a knee extension, the quads are doing the work. Nothing else is contributing. We can get an isolated variable and the output from that.

Number six, making sure they’ve built up to high outputs and intensities. If they haven’t done any isolated knee extensions in their program, a max test will destroy them, especially early on in the ACL rehab. You have to prepare the knee extensor mechanism for high force. That means the quads, the patellar tendon, the patella, and the soft tissues, including the quad tendon, too. All those create the extensor mechanism, which goes from that bone underneath your patellar tendon all the way up to your thigh. That’s the thing that is going to straighten out your knee. We want to make sure that this knee has been tested with that and has been prepared to do high force. You want to think of it as a progression over weeks or over months, shifting from higher volume and low intensity towards low volume and high intensity, building them up so the test isn’t a shock to the system. What I mean here, is that if you’re early post-op, you should be doing knee extensions. You should be doing them in a very strategic way. You might have some isometrics done at 90 degrees at a light intensity, and then build up over time to let that intensity increase. And then yes, you might hold it for a duration of 30 seconds, 45 seconds, and then slowly bring that down and have higher outputs of effort. 

In addition to that, you will also be trying to do knee extensions. You want to have some weight on the end of the ankle. And maybe you start with high repetitions. Maybe you’re doing 15 to 20 to start for a few sets. Maybe you don’t go the full range of motion, 90 to zero. You might go 90 to halfway to 45 degrees, 30 degrees. But the thing is, we need to build them up towards higher outputs. So that’ll slowly look like, alright, if we’re doing 15 to 20 reps, then we’re going down to 10 reps, five reps. But that’s over a course of weeks and months. That’s going to be super important here, and making sure that the output or the intensity of it is matching what the reps are. If you’re going to do five reps, you’re going to be doing heavier weight. You shouldn’t be doing a weight that you can do 20 times that you’re doing for five reps. That’s not a stimulus. You need to do something that you could maybe only do six, seven, eight times maximum with the weight assigned. And maybe you’re doing it for five reps at a time. 

But what I’m saying here is that this needs to be built up over a period of time. There needs to be some gradual exposure to it because what I see happen sometimes is that ACLers, they’ll go and get tested somewhere. Maybe it’s with their surgeon’s office, or maybe it is somewhere else that doesn’t do the testing. They haven’t been doing any knee extensions or open kinetic chain. And as sad as it is, the belief out there is still very strong that people think it’ll stretch the graft. And we have research to refute that at this point, because walking itself puts more stress on the ACL graft early post-op than an open chain knee extension when you’re putting a very light load on it. The other thing too is that when you are between 30 to zero degrees of knee extension, that’s where the ACL is being on tension, especially between 90 and 45 degrees. You’re not putting the ACL on any stress, so you’re good to rock there. 

We should strengthen the quads and do knee extensions. So that’s going to be really important though, because when people go to get tested and do an isokinetic test at three months or six months, and they haven’t been doing much knee extensions, they haven’t really been training for the thing that they’re going to be doing. And I’m not saying we need to get good at the test. But more so, we do need to incorporate that thing to get it stronger. When you go to do a max effort, you’re used to it. Even if someone’s asking you to go, hey, run a 5K at least have 1, 2, 3 miles in your tank. Don’t just be running, a quarter of a mile on a track, and then all of a sudden someone’s asking you to run a 5K. Let’s get some reps in the tank so then that way you’re used to it, ideally running a 5K. You can test it with a true exertion and what’s accurate.Make sure that you have built up to high outputs and intensities. 

And then number seven, the last thing is it’s not a pass-fail test. Just know these tests are not pass-fail. A lot of times, people look at it as man, if I get over this point, I’m good. I get it. We’re trying to achieve getting that quad to, I know the biggest thing people want to see is, can we get that deficit to less than 10%? Can we get the absolute value to around 100% body weight or 3.0 Nm/kg? Can we get there? Yes, that is everyone’s dream in this process, and to surpass that. But at the same time, like just know that testing is not a pass or fail. Every test is just a data point. The goal is to educate the athlete and the ACLer that we’re not judging success or failure. We’re not doing that. We’re collecting info, we’re looking for gaps, we’re looking for asymmetries, we’re looking for progress or potential lack thereof, and then we get more targeted. We get more surgical in our program design. It allows us to move forward in such a very specific way. It’s like us being able to recalibrate the GPS based on more information coming in and being like, okay, so we’re on this path. We started here. Now we’re 20 minutes in of this three-hour trip, and now we are able to update based on how many cars are on the road, what wrecks we see, and maybe some detours. These are all things that are data coming in for us to adjust and calibrate to be like, okay, what is the estimated ETA now that we have this information? What are the most efficient routes? You might take the scenic route, who knows, right? But with that said, that allows us to recalibrate the roadmap and the route that we are going to take. I think that’s super key in this process. S

Don’t overvalue the first test; test regularly in a serial process. Respect the pain because that could be potentially a limiter. When we’re doing this, and we might be testing tolerance over true strength. Manage the setup, isolate, and make the system rigid. Eliminate compensations as much as possible. Build towards higher outputs. It should look like a step-by-step approach versus this on-and-off switch, I’ve never done this. Now go do this. And it’s a high output, not in this process. It should always be built up and should be a graded approach. Treat every test as data, not like a verdict or not this final end-all be-all. These are the small details that make a huge difference in how we interpret results and ACLers will experience this through the testing process. But that’s going to be really important because I think testing has this kind of feel around it, of make or break it. I think the nuances and details of this are important. I think also that we just need to know that it’s not just going to be this like our magical day. It’s just information for us to know, okay, have we at least met this minimum criteria? And that’s why we need to look at it. It’s not like, all right, I’m 110% there. Have we met this minimum criteria to get to this certain point? And okay, what does that calibration/recalibration look like as we move forward?

I hope this helps y’all. We have ACLers who get tested, and there can all be all these feelings around it. But I was hoping that this can just be informative of just not putting too much stock in things, understanding the sequencing of it, the nuances of how important that is, and also just the buildup and perception of it, because testing is so important in this process. 

First off, I hope you’re getting tested. If you’re not, then that is a major red flag. Basically, tell me you’re not a good updated provider without telling me you’re not a good updated provider is if you have to ask about strength testing, if you ask them, do you do isolated quadricep testing? Do you use anything to measure it? They say, I don’t know what you’re talking about, or we’ll get there. Or, you’ll kick it into my hand. If they don’t tell you, or if you ask, there are three main options. Maybe something else exists that I’m not familiar with. But right now, they could do a repetition maximum on a leg extension. If we’re talking about quads, like a three to five repetition max, maybe one using a dynamometer. that is anchored, which gives an objective value, or an isokinetic dynamometer. Those are really the three things. 

Could we explore other potential options? Yes. But in reality, those are our methods of getting objective data and the way for us to make sure we can vet the professional or make sure that we know what they’re talking about and they’re legit is: do they test? That’s my general litmus for okay. They’re at least up-to-date enough to be doing strength testing and making it objective and making sure that they can explain that to you. 

The other side thing, I’m going to note because I’ve just been hearing this a lot lately, is that PTs have been dodgy with ACLer’s questions. They’ve just been like, ah, we’ll get there. Or we can talk about that. Or they just make something up. You can tell—red flag. Just something to share with you guys because we have a lot of these calls, talking with a lot of ACLers,s and it’s super frustrating. But I want you guys to be equipped. I want you guys to be ready for this process, and not be a statistic in this process and that starts with educating yourselves and making sure you find the best care for you. So that’s going to do it for today. If you found this helpful, please share it with somebody, whether it’s another clinician, an ACLer. If you do not mind, what helps us the most in this podcast and getting reached to serve more ACLers in this whole community is to leave us a review. That would be huge. Spotify, it takes literally three seconds. On Apple Podcast, same thing. You don’t even have to say any words. Don’t say any words. If you have good words to say, say it. If you don’t have good words to say, then maybe don’t leave it. I’m just kidding. Do whatever you feel is in your comfort. I appreciate you guys. Thank you for this community. Until next time, this is your host, Ravi Patel, signing off.