Limb symmetry index is often used to measure performance and determine return to play.
Makes sense, but what if the other side isn’t perfect?
We prefer to look at more than just LSI, but there’s a bunch that goes into it. We discuss in this episode.
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#AskMikeReinold Episode 350: Is Limb Symmetry Index Our Goal?
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Show Notes
• Return to Play Testing After ACL Reconstruction
Transcript
Student:
Meredith from Nashville asks, “I’ve always questioned the use of comparing strength to the other side when coming back from surgery like ACL. It seems like the other side is optimal, too. Do you use Limb Symmetry Index to help determine return to play?”
Mike Reinold:
I love this question, and I think a lot of people get this question. This recently came up to me somewhere. Maybe this was in our sports PT mentorship. Dave, Dan, I forget where this was. It was about the shoulder too and about symmetry. Man, it’s kind of crazy. I mean, oftentimes the uninvolved extremity isn’t where you want it to be, so what do we do with limb symmetry? Let’s start with this. Let’s go in a different order.
I’m going to start the strength coach side with Jonah and start with this saying, in our healthy athletes, talk to me about limb symmetry in our sports science testing. How symmetrical are they? What are you looking for? What do you want them to be? Do you want everybody to be symmetrical? I’d just be curious to hear the thoughts from the asymptomatic, like the non-injured person first, but what are your thoughts on limb symmetry and your goals from a sports science perspective, Jonah?
Jonah Mondloch:
Yeah, so I think I’d start by asking the question of if we have two athletes in front of us, one who, say, on a counter movement jump is well above average but they are asymmetrical, or another who’s at or below average and they’re asymmetrical, which one of those do we think is going to be the better athlete? I’m taking the one who has better performance numbers but an asymmetry all day long. Then I think your point of looking at healthy athletes is also really important. We do see a lot of asymmetries in our healthy athletes, in people that have never had a major limb injury, but then we also do see the people who had, say, a bad broken leg when they were in middle school, and to this day they still have a 12 or a 15% asymmetry.
That’s probably not ideal, but I think it’s almost impossible to disregard the impact that that could continue to have on somebody forever. We will still use strategies like more single-leg work for them to try to bring up the strength in the previously injured side or the side that does perform at a much lower level. Yeah, we do very frequently see people with asymmetries. I’d say once you are over that kind of 10% mark, it starts to be something that we might look into a little bit more, but I’d honestly say there’s very few athletes that always test symmetrically.
The other little piece I think would be how consistent their asymmetry is, where there’s people who, one week when they test, they’ll be on the left side a little bit more. The next time they test they’ll be on the right. Or one week there’ll be 10%. Another week there’ll be 5%. I think those are less worrisome. Whereas if it’s your person where you look at every rep they’ve ever done on a counter movement jump and they favor the right side, that again might be a little bit more of a yellow flag that we might want to address.
Mike Reinold:
I love it. So it’s not uncommon to see these asymmetries. When you see them, you said is 10% the threshold that you use? When would you program differently based on that, for that asymmetry? When does that trigger to you that, “Hey, this is something we need to address?”
Jonah Mondloch:
I think it might vary a little bit, honestly, depending on the age. Where if it’s an older athlete who’s been in the gym for a long time and they’re pretty healthy, especially if it’s a baseball player, where they do play an asymmetrical sport, if I saw 10%, I honestly probably wouldn’t do anything different for them. Maybe they get over that 15% mark. Now I’m like, “Okay, we do need to address this.” Whereas if it’s a younger athlete who hasn’t been in the gym as much and they don’t play an asymmetrical sport… Soccer still would be. Maybe they’re a football player. Then I’d probably start by just giving them more of their lower body work as single leg variation so that they can’t just rely on their stronger side. I might not give them any extra volume on the weaker side, but just spend more time doing single leg work and see if that asymmetry starts to shrink over time.
Mike Reinold:
I love it. That’s a great approach. Great stuff. Diwesh, what do you think? Anything from your perspective on that?
Diwesh Poudyal:
Yeah. The only thing that I was going to add on top of what Jonah said, and I think he covered most of it, is we definitely do want to highlight or take note of what kind of sport they play. If the sport forces them to be asymmetrical, and the asymmetry is almost like a competitive advantage for them, we’ve got to keep that in mind as well. That’s not something that we want to try to change too, too much. Imagine a basketball player that’s incredible at taking off of their left leg, and they happen to push way more on their left leg on a counter movement jump on the force plate. Do I want to change that? Not necessarily. That’s the leg that they’re going to fly over people and dunk the ball with, so it’s not that worrisome because I know that they’re being forced into that asymmetry, and it probably gives them a little bit of an advantage. We see that all the time with our pitchers, too, like Jonah mentioned a little bit.
So just making sure that we’re keeping that into account. Then if we do see that consistent 15% asymmetry, and we’re starting to have some pain, we’re starting to have some dysfunction showing up as far as movement patterns not looking the way they should and things like that, then we’re probably going to dive into it and maybe start addressing it by giving them more single leg work with more sets on that one involved side or whatever. Stuff like that, but until we’re really figuring out if that asymmetry is a big deal, we’re not really jumping to correct it right away.
Mike Reinold:
Yeah. I would hate for somebody to have their left stronger than their right, like you said, but they’re a basketball player. They’re left-dominant, and you just start focusing almost exclusively on getting that right side stronger. Right?
Diwesh Poudyal:
Yeah.
Mike Reinold:
It seems like that would be counterproductive to what they need. Yeah. Jonah?
Jonah Mondloch:
Yeah. One last thing I’d add in is that the cause of the asymmetry might not actually be strength. An example would be if you were really limited in ankle dorsiflexion in one of your ankles, you’re going to have a really hard time loading deep into that side on a counter movement jump. So, I think it is important to make sure we’re still using our other assessment tools to try to figure out what it is that’s causing the person to rely on one leg more than the other.
Mike Reinold:
That’s super interesting. I bet you a lot of people don’t think of that. That’s awesome. So PT perspective then, so that’s healthy people. That’s normal people, which by the way, that was tremendous information for the rehab crowd to understand about healthy people, too, but from the PT perspective, what do you guys think? Dave, you want to start?
Dave Tilley:
Yeah, my first two cents is just, I think as Jonah was just saying, as a general rule of thumb, I would say PTs tend to strength test isolated muscles. We’re looking for asymmetries with dynamometers, so in a hip exam I’ll test out five to six different motions which are correlated to more so one individual muscle group or muscle motion you would say, but I think that in the strength conditioning side, correct me if I’m wrong Jonah, but it’s more like jumps. It’s more like hopping, it’s more running. I don’t think they’re doing a lot of dynamometry testing. So, I think the lens in which you view that from is very important, right? Because as PTs we’re oftentimes looking for an injury-based strength difference.
I think I always go back to some of the stuff related to soccer and groin strains. That individual dynamometry for groin testing is sometimes correlated to who might have more risk of an injury in season with sprinting. So, those tests were dynamometry adduction tests that are all along. I don’t think they looked at any kind of movement jumps or any squat jumps at all. So, I think the lens in which you view it from is a lot of PTs are looking at dynamometry individual muscles. I’m sure Lenny is going to talk a lot about like ACL stuff, extension, and torque with individual stuff, but I don’t know how strong the literature is for PT on asymmetry in counter movement, single leg depth drops versus asymmetries in quad raw strength.
So yeah, I just think that’s important. We’re lucky where we talk to each other all day long, but if you’re in just a PT clinic, you’re probably not even ever seeing a force plate in your life and understanding some of those jump measures, where if you’re on the strength coach side, you probably only look at ball data all day long, and you probably wouldn’t understand the dynamometry piece. So, just my two cents.
Mike Reinold:
I love it. I think that’s a good segue to Lenny then and start talking about this with, let’s say, the ACL population. What are your thoughts on limb symmetry and your goals? What’s your current headspace with that, Len?
Lenny Macrina:
Yeah, it’s definitely evolved and it continues to evolve as we learn more. The person asking the question brings up good points. We used to just use LSI, and at that time, testing both legs. You don’t know the history of that other leg and whether or not they had a previous ACL, which seems to be more popular now, or a previous injury, or the fact that they tore their ACL six, eight months ago. You’re now testing that surgical side. What has the contralateral side been going through for six to eight months? It hasn’t been performing at the highest level in a game or something like that, so it has probably lost some strength. So now our LSI numbers are lower from a baseline.
That study that came out… That epic study that came out from Delaware in 2017 was a great example of that. That showed if you compared people, if you use their pre-hab numbers and looked at their involved side, only about a third of the people actually passed LSI testing, versus if you used the contralateral side at the time of testing, many more people passed their tests. So, that study changed things in my head, and that was what? Seven years ago.
Now for me, if I get somebody pre-op with an ACL or any surgery, I try to get as much information as I can testing on them so I have a baseline as close to the injury as possible because that uninvolved side is probably relatively strong compared to where it will be in three, four months when you begin testing them. So, get baseline testing on your pre-hab people. I use the 90 degrees of flexion isometrics of the quad and hamstrings, and that’ll be my baseline. That’s at least what we have to get back to when we’re trying to get them back down the road, so using that.
There are papers out there. I shared it with the team, and we use this as kind of a mental reference. There are papers out there that look at values, the torque values of people, healthy individuals, of males and females in certain sports, soccer and team handball because a lot of it comes out of Europe, of baseline torque values in individuals, like I said, male and female. So, a female should have at least 2.3 Newton-meters per kilogram of strength in their quads, or a male should have 3.0 Newton-meters per kilogram of strength in their quads at least. So, using those reference points of papers that are out there. They got Nicky van Melick in 2022, Jay West PT, and then the Risberg paper in 2018, I believe it was, are some papers you can look up that give you some of those values of people so you can have at least a reference point because we know people’s legs get weaker as rehab goes on. Initially, and then they begin to build some strength over time.
So I think having those reference values and not necessarily comparing it to their other side… You can, but I would also keep in mind those reference values. I’m getting long-winded here, but if that contralateral side has 3 Newton-meters per kilogram, and your surgical side has 2 Newton-meters per kilogram, that’s a 67% LSI, so they’re 33% weaker. You need to get them… At least, literature says, 90% LSI. I tend to want to bust through that window, that ceiling, and get them at least 100% and get them symmetrical as much as possible. Knowing what Jonah said, I’m asking them, in their history, is there anything that could relate to that they may not have symmetry? Most people don’t have symmetry. So I keep that in mind, but if they can get within that 5 to 10% window, I’m happy overall.
Mike Reinold:
How many people get to that 5%, 10% window, do you think?
Lenny Macrina:
Most of my people do get close, and that’s a huge criteria for me. It’s one small piece of the puzzle. It’s how they’re performing in the clinic with their workouts. How are they doing with agility stuff? What’s their movement jump? What’s their drop vertical jump testing, both double leg and single leg, later on in the process? Are they handling running and cutting and their knees are not swelling? They’re not losing motion? They’re pain-free? I’m taking slow-mo videos of them doing certain activities. I should give them feedback on what they look like and how I think they’re doing. So, we try to blend all that in and not just focus on one test. It’s blending that big picture in.
Most people do get symmetrical. It is tough, though. You’re chasing. If you’re using the other leg, you’re chasing that leg because it’s getting stronger as well. Probably faster than the surgical leg is getting stronger, so you’re chasing that. I think Anthony Videtto, one of our PTs, shared a paper that just came out, I think it was last year or two years ago in JOSPT, that that contralateral leg gets stronger for at least six months. So, that person who’s going through the testing is upset and frustrated that their numbers are all over the place on their surgical side because the contralateral side keeps getting stronger. That’s why it’s a tough index to use if you’re using the contralateral side because it’s also evolving as the strength is improved. So, keep that in mind as well.
Mike Reinold:
Yeah. I mean, some of the limitations with limb symmetry. I mean, great points with that. So what do you recommend then, Len? I mean, is it body weight ratios? Is it torque ratios?
Lenny Macrina:
I use body weight ratios. I try to get baseline testing and I use reference values from the papers that I mentioned, that Risberg paper and the van Melick paper. I keep those in mind, that females and males, depending on the sport they play, depending on their age, I want a certain number. If you have somebody who’s testing out at 1.9 Newton-meters per kilogram, but the other side is 1.8 Newton-meters per kilogram, that’s weak. You want a female to be at least 2.2, 2.3 it seems like, and higher, and I’m educating the person. “Yeah, your LSI looks great, but overall, we need to get you stronger for your body weight.” It happens more frequently than you think, and that’s probably one small reason why they’re in the position that they’re in. They were doing a sport and just not strong enough to handle it.
Mike Reinold:
I’m glad you got to that because I feel like I see that a lot with our younger athletes, is that they don’t look good as a whole. Their total body stinks, and we’re using their other side to say, “Well, congrats. You’re 90% as stinky as the other side.” Well, that’s not good. Right?
Lenny Macrina:
Right.
Mike Reinold:
That’s not the good baseline sometimes. Right, but who else? Diwesh, did you have something to add?
Diwesh Poudyal:
Yeah. I just wanted to add one more layer to what Lenny was talking about. The LSI is definitely important, but as far as return to sport goes, one thing that we see all the time, and I’ve definitely seen it recently with some of the people that I share with Lenny, is their LSI will look good. Their isometric testing for quad, hamstring looks pretty good. They’re within that 10%, let’s say, but then we get them on a counter movement jump or a single leg counter movement jump. They’re still pretty asymmetrical, right?
Lenny Macrina:
Yeah.
Diwesh Poudyal:
So, what that’s essentially telling us is the baseline strength is there. The isolated strength is there, but there’s a whole heck of a lot of layers of complexity, intensity, the rate of force production required to be good at sports, and things like that that we’ve got to address as well. So, making sure that we’re not getting too obsessed with just the isometric strength and making sure that we’re respecting the complexity of movement as things get more challenging and programming it to affect some of those things as well. We do quite a bit of velocity-based training on single leg and double leg to make sure we try to bring that up, weighted jumps on single leg and double leg to try to bring that up. So, just making sure that we’re not getting too, too hung up on just the isolated isometric strength.
Mike Reinold:
I love it. I love it. So to Dave’s point, don’t just focus only on force plates. To Diwesh’s point, don’t just focus only on the handheld dynamometer. If you’re really not doing both, you’re missing out. You’re missing out. If your clinic sees a ton of ACLs and you don’t have force plates, you got to get force plates. But Dan?
Dan Pope:
Yeah. One last thing I was going to add, and this is something I’ve changed over the course of my career, but you have a patient post-op knee, let’s say, and we’re going to basically do a return to sport testing somewhere between six and nine months, right? See if they’re ready. I used to just hang all the rehab on that one day. We do all our tests on one day like, “Oh gosh, we’re not where we need to be.” Since we have force plates, we do a lot more serial testing, and it’s crazy, the variance you get from week to week, from session to session.
So, one of the things that I think is important now is that you’re just taking a lot of measurements over the course of time. I know it’s a pain in the butt to measure frequently, but just seeing the trends and data. I would see people do a counter movement jump. One week, the left side is 20% more than the following week. It’s actually the right side, and then it switched and it flips. Then, over the course of time, you see some trends. But I used to just hang my hat on that one test like, “Oh, looks like we’re way off,” or, “It looks like we’re good.” I was probably wrong just because there’s so much variance between those tests from session to session.
Mike Reinold:
Really good point, and there’s probably more variance in somebody that is post-operative. Coming back from something, their susceptibility to having a bad day, sleeping poorly, or something like that, that’s going to expose their asymmetries and limitations even more than a healthy athlete. Awesome. Well, great job, great question there. I think we handled that pretty good, Meredith. Hopefully, that helped. I think it was a great discussion just in general on how to serial test these people and just make sure we’re on top of them, so great question. If you have anything like that, head to mikereinold.com. Click on that podcast link, fill out the form, and please subscribe, review us, rate us. Apple Podcast, Spotify. We’ll see you on the next episode. Thank you.
