Episode 2: Tests that we use at ProActive

The following blog post is a transcript taken for my podcast with slight edits. So it is written as it was spoken. Please excuse the grammer!

Welcome back to the Proactive Perspective podcast. In this episode, I'm going to talk about the different tests that we perform at Proactive Athletic Performance. Before I get into today's content, just keep in mind that this podcast and the blog post are not to be taken as medical advice or knowledge, but more for entertainment purposes. If you currently have an injury or you have a previous injury, seek out medical attention from a physician or a rehab specialist.

Now at Proactive Athletic Performance, we perform various testing with the higher tech equipment that a lot of other clinics don't have. So we provide testing services and we do a variety of tests. That's not to say that you can't also perform other tests or if you don't have access to the equipment we have that you can't use a proxy. This is just what we have found that is the most predictive of performance or injury risk. So when you come into Proactive, we're going to do two different pieces of equipment with testing. One is a force plate assessment and the other is on an isokinetic dynamometer. If you don't know what an isokinetic dynamometer is, you can go back and listen to the previous episode where I kind of talk the basics about isokinetics for testing and training.

Now the first test I perform when people come in after they're warmed up is we hop on our force plates. When you do a vertical jump, that's about 30% of the force and power is going to come from your knee. About 30% comes from your ankle and about 30% comes from your hip, right? So, it's not completely isolating your knee, but it does allow us to get, 30% contribution. another way that people will assess function in hopping is in a horizontal hop. And it's usually like a triple hop crossover jump. The problem when you do that is only 13% of the contribution of force and power comes from your knee. So doing a vertical jump allows more of the knee to be the contributor. but it also gives us very precise numbers. When you do a horizontal hop, all you can do is really measure the distance that somebody jumps. but you're measuring just in inches, centimeters and you're using a tape measure. But when you're on a force plate system that really gets very precise output in numbers that you can objectively analyze.

 And on there, I like to do a double leg and single leg countermovement jump. And what a countermovement jump means is that you start in a standing position with your hands on your hips. You drop down really fast and then jump up as high as you can. And we don't let you use your arms because a lot of the power that you generate when you jump is actually generated for swinging your arms up. And we're trying to get as close as possible to isolating the legs, So we don't let you use your arms for it. And when I do a double leg jump, essentially what I'm looking for is how symmetric are you, So if you were to do a maximum effort jump and you don't have an injury, you're probably going to be using one leg slightly more than the other and we want you to be around 10% more on one side or the other and not really that far outside of that. But whenever you have an injury and you're coming back from that injury, you're naturally going to use one leg more than the other. It's usually your healthier side is going to be generating more of the force. if I have you jumping at just, submaximal, maybe 50 or 75% of your effort, you're going to probably be much more symmetric using both sides evenly. But it's when we have you go as hard as you possibly can or jump for as high as you can, that's when you're really going to start biasing one limb over the other. So, we are you using one leg more than the other? And we break it down to the various aspects of the jump. You have the lowering phase, right? That's called the eccentric. And then you also have the propulsion or the raising phase. That's the concentric, right?

So I want to know are you using the one limb more on each of those phases. Then I also look at it another way is when you're at your peak takeoff force at that highest moment of maximum output at takeoff are you symmetric or not? And then how are you landing? Because that gives us a lot of information that you can use in your next phases of rehab. usually I'll have somebody, six months or seven months after they've had an ACL surgery, and they might be, 15 to 30 or even up to 50 or 60% more on one limb or the other, depending on how they're progressing. But they can then use that knowledge when they're performing their exercises with their physical therapist or with their strength conditioning coach or just on their own if they've been discharged.

And they can really use that knowledge and really try to get that symmetry, down, try to make it perfectly even. Now, sometimes people will be completely symmetric even at six months out because they've really focused in on, dialing in and using that limb, right? It's not as common, but we do see that. And sometimes they'll be symmetric on one phase of the jump but not others. they might lower down pretty even but as they actually go to power off into the jump and the actual propulsion phase they might bias one side more than the other or everything might be completely symmetric until they go to land right so we use each of those phases to help figure out how they're actually loading and how their body is choosing to perform that task.

 I then go to a single leg countermovement jump and on this it's the exact same thing. Your hands are on your hips. You're standing on one foot and you're jumping as high as you possibly can on your right leg and then your left leg. And with this when you do it that way, you don't have the opportunity to use one limb over the other because you're forcing 100% of the output through each leg. So this gives us great metrics. we can look at jump height. That's your ultimate outcome with it is how high can you jump. so it lets us see just exactly what percentage higher you're jumping on one leg or The other metric I like to look at is the RSI modified. And this takes your jump height divided by the amount of time it takes to perform the jump. And this is kind of think of it as your jump efficiency. If you're playing basketball, for example, and you're going up for a rebound, and the person that you're rebounding against has the exact same jump height as you can. So, you hit the exact same height, but you're able to get there before the person, right? You can jump faster than them, So, you're going to be the person that gets that rebound over them. So, I look at that the RSI modified as well.

I then break it down to how much better you are on one limb versus the other in the different phases. I like to look at, the lowering phase. It's called the impulse. So, that takes the forces that you're generating multiplied by the time it takes to do it. So it's kind of looking at your force over the entire phase of lowering which is called the eccentric braking or the concentric impulse the raising up portion. So if I see that you have let's say a 30% better jump height on your healthy side I can then look at where is it Is a lot of that coming from your eccentric braking, the lowering phase, or is it coming from the propulsion phase or the actual jumping phase? Or is it a little bit of both? Is one more so than the other? I tested a young man last week and he was 50% better in his  height on one limb over the other. But when we looked at his eccentric, he was 60% less force on his surgical side. But on the raising phase, the concentric, he was only 30%. So I, told him, hey, we want to work on both aspects of your jump. But, we really got to narrow down the eccentric or the lowering phase, the breaking side of it. Until we clear that up, it doesn't matter how much you're going to be propelling yourself up, we really got to go for that low hanging fruit. So that just allows us to isolate each leg and to see where those forces are coming from. and another thing I forgot to mention when we do a force plate assessment, that's looking at the entire limb as a whole, right?

Then after we perform the force plate assessment, I then move to the isokinetic machine. And at Proactive, we use the Humac Norm isokinetic system from CSMI. There's other brands out there, but the HUMAC, it's just you have more advanced testing options. it's a little bit more user friendly. It's a bigger seat. It's more comfortable for the patient. So, in my opinion, it's a little bit better system than some of the other ones out there. Now, that being said, I also work with CSMI. I'm their education director. I do the installs in the US, so I'm a little bit biased towards their system. So, I need to, get that little disclosure out there. So, when we go on the isokinetic system, I first do an isometric test. With isometric, that just means that, I line them up to the seated position, almost like a knee extension machine, but I lock the dynamometer, the movement arm, so it's not going to move.

And then the patient is going to push or pull into the pad and that is going to then the computer system then measures and records how much force torque output they're able to generate with each muscle. So we do it a couple different ways. First I have a max torque buildup so they have up to 5 seconds to push as hard as they can into the pad. this allows us to see exactly, if one limb is doing, let's just say, 200 foot-lbs and the other one's doing 100 foot-lbs, it gives us, the percentage of difference between the two. For that example, you'd be about 50%. Right? but it gives us a precise measurement.

It also lets us see exactly how hard they're able to push or pull relative to their body weight because ultimately we want for any measure that we record that there's only a 10% difference between limbs, right? your non-injured side. 10% is your max that you're wanting. But we also want to know, are they strong relative to their body weight? If I weigh 200 pounds, I need to be able to control and have enough force to control 200 lb. But if I only weigh 120 pounds, I only need to be strong enough to handle 120 pounds, So the isometric is really good for measuring that, but you can also measure that, with a handheld dynamometer or a inline dynamometer.

But one thing that our system also does is it allows us to do a rate of torque development test. So that's where I give the patient just a half a second to explosively push into the pad. And this is going to see what that torque difference is at 400 milliseconds because when you have 3 seconds to build up your torque, even an injured limb can build it up pretty high. But we don't have, 2 or 3 seconds when we're playing sports or going downstairs or doing any other functional activity. So, by using that 200 millisecond mark, it lets us see how much force they actually have access to while they're doing these functional or athletic activities. And we usually see a bigger difference in torque in that early contraction because that's something that doesn't come back until later in the rehab process. It's neurologically driven. It's not just how hard can that muscle push, but it's how quickly it can contract, right? It also gives us a measure of the rate of torque development. And this reads in foot pounds per second. I always explain this to patients as miles per hour. if you have two cars at a dead stop and you have them both slam on the gas, how many miles per hour is one car going to be able to take off at versus the other. Now, because we're on a dynamometer, it's reading in foot pounds per second, but it can give us an exact difference between the two. All right? So, that's another great measure that you can look at. because sometimes if somebody has good strength after an injury and we can test them and they have good strength, but they may still be having issues and lingering effects, it might just be that they can generate good force, but they can't generate it fast enough to be able to handle the demands of sport, so gives us really good metrics to look at.

If somebody's early in the rehab process and they want to know if they're able to jog yet, research tells us that if you can generate a certain percentage of your body weight and if you can produce a percentage compared to the uninvolved limb that you shouldn't have many issues returning to running or we have different metrics for returning to plyometrics or high-speed agility tests, right?

So you can use these numbers to assess how ready they are for that. the downside of isometrics is the joints not moving, right? We're putting you at the strongest position that you can generate force, So it gives you the best opportunity for a maximum output. But when we're playing sports or going downstairs or whatever it is, we're not locking our knee in a position. it has to bend and straighten through the range of motion. So that's where the isokinetic test comes into play because on isokinetic what we're doing is we're setting the machine to a certain speed and then we're having the patient push into or pull against the dynamometer. So it's going to then record their torque throughout the range of motion. And because we're setting the speed, it allows the resistance to accommodate.

So, we can see at different points where you're supposed to be strong in the range, are you building up torque appropriately? And then as your knee straightens out your torque is supposed to go down, is it going down appropriately or is it, really failing at one portion of the range of motion or the other. So, I liken the isometric to an X-ray, right? It gives you good information, but it leaves out a lot of detail. But when we get into the isokinetic test, that's like an MRI. It's uncovering much more detail that you would get that you're missing out with an X-ray. and then even with isokinetic testing, we have a couple ways of doing the standard isokinetic test, which is a really good test, it has the patient push up against the machine on the way up, but then pull down into the machine on the way down. And this was a test that was designed in the, 1970s and then in the 1980s and it's just kind of remained the gold standard. But the problem with that test is that's not how our muscles function, especially the quadricep. It mainly functions as a decelerator. So, it's working against gravity. It's what you're using to absorb load as you're making a change of direction or cutting or even running. You have to absorb that load. So, unless you're testing the eccentric mode where it's decelerating, you're not going to know how that muscle is actually functioning. Now in the 1980s and in the 1990s there's a group called Chattanooga. They had the product called the Kincom. They developed their machine was able to actually assess the eccentric mode of contraction. So that was a big game changer. Problem is that company didn't last as long as some of the other ones out there. So its technology really didn't hit the mainstream. And at that point a lot of research had been done on isokinetics. So, it's not that eccentrics is new. It's just kind of new to the masses because now the Humac system it performs eccentrics really well. and it's just kind of now getting out to, a lot of therapists, athletic trainers that you can actually assess this. So, by doing that, you really get a much more in-depth view on how the muscles are going to perform when they're being challenged in the mode of contraction they're actually going to be used on the field. So, I like using the advanced isokinetic test with my ACL's or even people who are just, maybe they don't have a surgery, but they're looking to get back to their sport, there's a lot more forces that go through it. so, you can't do this early in the rehab process with any injury.

Soif somebody's early in the rehab, I'll use the regular isokinetic test because that's a good way of at least assessing through the range of motion, getting both muscle groups, but it's not going to give you the eccentric. So, I really like using that advanced isokinetic test. the other thing that we do with it is we have what's called the interrupted stroke because when you're doing a concentric eccentric test. So let's say for the quad you're pushing up on the way up but then the machine comes back down and you have to keep pushing against it. that kind of throws off your nervous system a little bit. it's hard to know how to do that test. So by using the interrupted stroke option that allows you push up to the top and it stops and then we start the machine as it comes down so the patient's able to continue pushing all the way through the end of the motion without having to worry about the machine changing its motions back and forth. So, it's a really good test. It uncovers a lot of information that you're not going to get with the standard isokinetic test or even with an isometric test. And with each of these we have different metrics that we're looking for and we'll have a whole other episode on metrics but we want to know how does that the injured side compared to the non-injured side right how is the opposing muscle groups performing. We need to have a certain balance of let's say the hamstrings versus the quad or in your shoulder your external rotators relative to your internal rotators.

But then we also look at how is one mode of contraction like the eccentric how is it performing relative to the concentric numbers right and we take all of this data and we try to compile it and then there's always context to everything right I forgot to even mention how are your muscles performing relative to your body weight right so we take all these metrics and what we're doing we're not giving you necessarily a pass fail we're just finding out what elements are still deficient. And we know that you need to have various elements in order to return to your sport safely. You need to have a good strong quadricep. It has to be able to fire quickly. It has to fire in various modes of contraction. Your hamstrings have to be able to fire and produce torque relative to your body weight and relative to the quadriceps. So all we're doing with testing is we are quantifying the various elements that you need to have to get back to your sport, We combine that with how you perform in the functional task of the counter movement jump. in the future I'm looking to also add timing gates so we can do the 505 test and see what is the exact amount of time it takes for you to do change of direction from a max acceleration sprint. Right? You're taking all these different elements and you're trying to just quantify that.

It allows the patient, the physical therapist, the doctor to see how close you are in returning to your sport and where you really need to be focusing your efforts in your phase in your next two to three months. where do we really need to focus? are our hamstrings nearing their normal strength but the quadricep is still lagging behind? are you getting good eccentric neurologic contraction or is that muscle quivering and shaking so much that it can't even generate torque? do you have good quadriceps contraction in each mode? It just needs to increase in one mode or the other or even both. Right? It just allows you to see exactly what deficits remain so how to progress in these next phases.

So I'll be covering some of the metrics that we look at in upcoming episodes. I think that's it for today. if you have any questions, you can always get a hold of me. my email is daniel@proactiveathleticperformance.com. You can also contact me on our website, which is proactiveperformance.com. So that's it for today, guys. Thanks.