In this episode, your hosts Kim and Jeroen will be discussing NIRS. What is Near InfraRed Spectroscopy? What does it do? How does Train.Red use it? How is it used to measure muscle oxygen levels? And most importantly; What can you do with it? Want to know the answers to these questions as well as the difference between pulse oximetry and heart rate? Press play!
Introduction: who are the hosts?
00:00 (Kim ter Stege)
Welcome back to BE AHEAD. podcast by Train.Red. My name is Kim ter Stege, I'm part of the Train.Red team and I'm the host of this podcast. I'm a sports enthusiast. I started my fitness journey after losing a lot of weight and I got very interested in fitness and health. I'm also a content creator. You can find me at @kimterstege across all platforms and I also have my very own podcast. I'm here with my co-host Jeroen.
00:24 (Jeroen Molinger)
Hi, my name is Jeroen Molinger. I’m the Lead Clinical Exercise Physiologist at Duke, at the Human Pharmacology and Physiology Lab, Research Program Director of the lab, and also Research Program Director of Duke Heart Transplantology at the Cathlab. My main focus in the research we do at Duke is all related to assessing muscle physiology and cardio-respiratory function.
Glute vs quad dominance
00:44 (Kim ter Stege)
All right, so last episode we talked about NIRS and gave a little bit of an introduction into what it is exactly. So if you guys didn't listen to that, I would suggest listening to the last episode and then coming back to this one. Today we're going to talk about how to actually use a NIRS sensor during sports and how to apply to your training and adjust accordingly. So Jeroen, last time we talked about NIRS and what it is exactly. Uh, to give a little summary with a NIRS sensor like the FYER from Train.Red, you can measure the, um, oxygen levels within your muscles, which of course is very interesting because you can apply to your sports and see what's actually going on within your body. We also talked about that you can measure the difference between left and right, and then also just different muscles at the same time. Um, but I'm also wondering, like in the, uh, fitness world, it's like very common for some people to be, for instance, quad dominant or glute dominant. Like even if they squat or just do a another exercise, some people just grow more muscle on the, on the quads and others on the glutes. Is this also a way to see with NIRS, like if you're more quad dominant or more glute dominant, and is there a way to measure that?
01:51 (Jeroen Molinger)
Absolutely, and there are two ways of measuring it. Um, the, the, the direct way of measuring if a glute or a, uh, uh, quad is more dominant is just with, with, we call it EMG. So you're measuring the amount of, uh, recruitment, so how fast a muscle can contract on a specific, when you do a specific exercise. Uh, but it's interesting that you can even do the same way in looking at how much is the specific muscle is using. So, um, and, and when you, you will, you will see when you are using the NIRS device, this, I think the, the, the, the, the biggest, we call it the paradigm shift when you will see that everyone thinks when you do a, an exercise, uh, um, like a deadlift and all that that specific deadlift is an exercise that is mainly being used or being done without oxygen. And that's not true at all because of course you do not breathe that well or heavy like you do when you run, but you're looking at the muscle itself and you can see how fast it really goes down in the, uh, amount of oxygen.
Conventional vs sumo deadlift
02:54 (Kim ter Stege)
Yeah, because you're using a lot of muscle power. So it should like differentiate very much in the, in the exercise. I'm just thinking about this, I don't know if this is true, but for instance, if you're doing a deadlift, there is an endless discussion if conventional or sumo deadlifts are better, and is there a way to see how your muscles respond to what form better? So for instance, you do that conventional deadlift with the sensor, see how your muscles respond and do a sumo after and then just compare. Is that also a possibility?
03:25 (Jeroen Molinger)
Oh, absolutely. I think what would be interesting if you do a different kind of methods to see, um, what the graph looks like, so it it this a dynamic graph, right? So you can put different sensors on your quads and on your glutes, on the left, right, even also to see, uh, which is the fastest in different methods, which is, is for instance, if you're more glute dominant, you will see that the first signal of change of using oxygen that the curve will go down is for instance, from the glute. And then you can even change if you want to have a change in your technique, you can see what do I need to change to have that specific dynamics being turned around that I'm more more quad dominant. And that's kind of the thing. But now you have visualization feedback where you normally will not have, you just try to do some different methods, like...
Endurance training and NIRS
04:11 (Kim ter Stege)
You just try to do it and see what worked better for you, but you can actually maybe like put it into visual to, uh, to see if you use the sensors. Um, I'm mainly talking about fitness now because that's my personal preference, but obviously this also is for cycling, running like any sports. So do you have anything to say about how you can use, uh, a NIRS device for different types of sports?
04:36 (Jeroen Molinger
Right. I think for the, the whole resistance, uh, piece of I think a very specific different piece than, uh, the whole cardiovascular endurance sports, um, where you have more prolonged, uh, time of assessing, um, uh, and of course you have very defined muscle groups that you're using. Uh, and mainly if you're comparing, for instance, bike with, with running is mainly where the, the, the primary movement, primary drivers of your, of your, uh, uh, movement are, are are the legs. So your, your quads, hamstrings, and potentially your glutes and, uh, your calves. I think when you're looking from an endurance perspective. It is interesting that you can see some specific zones from a muscle perspective. So can we, if you want to train and everybody knows it's on 1, 2, 3, and 4, and, um, so how do you define zone two? Not from your overall perspective, like, um, if you do it, if you did an FTP test, but more from a, uh, test where you can show does this muscle respond the same way like it did with a test? Mm-hmm.
05:43 (Kim ter Stege)
If you're talking.
05:44 (Jeroen Molinger)
Yeah, go ahead.
05:44 (Kim ter Stege)
Backtracking a little, talking about the zones, you're talking about if like for instance, a pace is sustainable, it's not sustainable like how your muscle is responding, right?
05:53 (Jeroen Molinger)
Right. Yeah. Okay. Yeah. Yeah. So I'm, I'm not sure, well, maybe we have, have to talk about a little bit further on in our, in our, um, episodes about for instance an exercise test, which you can do and I think what almost everyone does with who using Zwift or Peloton, uh, like the FTP tests. So how can you drive?
06:11 (Kim ter Stege)
Yeah, I think we can go into like specific sports and then see how you can actually use NIRS and what you can do.
06:!8 (Jeroen Molinger)
Yea, for sure. Exactly. Exactly. Yeah.
NIRS and performance06:20 (Kim ter Stege)
Yeah. Okay. So moving on to NIRS and how you can use that to measure your performance, but also how NIRS plays a role in recovery.
06:28 (Jeroen Molinger)
There are different, different approaches. Um, when we're looking at, just from a, um, perspective of movement, I would over-exercise or whatever you wanna do is I think it's essential to create your own baseline. So the number that you see from a NIRS device is, is not an absolute value. Like if you would do a, um, blood draw measurement like cholesterol, we know for sure this is the number and this is the reference number. And if you are in the high, in the low, then we know you are in good or in the, uh, in the bad. In the bad space, uh, for NIRS it's kind of different because there is a, um, not a well defined reference failure where a quad or a glute should be in. It's more looking at the dynamics. So how fast can you go down and how fast can you go up?
There's no standard 'baseline'07:13 (Kim ter Stege)
So is this more because it's not researched a lot or is it just very personal to each person?
07:!8 (Jeroen Molinger)
The thing is, it is personal that that's for sure, but also to make sure that you are measuring in a very small space inside that muscle because we're putting a small piece of light in a big muscle and we are only looking at that specific part of the muscle. And normally the depth of a NIRS would be around 1.5 centimeters tops. Uh, so you're only looking at the top side of the muscle, not even potentially in whole, uh, in a whole middle. And the heterogeneity of how a muscle is being distributed in the usage of oxygen is not homogenous. So when you're putting it this way or doing a more, and, and the high side of the lower side, that would definitely give you different numbers. So also on on on that, on that approach, make sure you are really defining the place you put your sensors in as always the same, You cannot change sensors on the, uh, for instance, from a, from a leg.
How to improve with NIRS
08:15 (Kim ter Stege)
The no, for instance, a quad is very big, and like you have to define like a spot where you're going to use it every single time.
08:22 (Jeroen Molinger)
Exactly, yeah. That's the most important. And then create the graphs where you do, um, yeah, some dynamics like for resistance exercises is, is a different way of using the muscle because if you do a, for example, you do a, you want to really drive your 1RM, so you do your 1RM test and when you have a very high recruitment of muscle and the muscle is really, really contract, when the muscle is on the upmost of the, of their contraction, so you're putting a lot of force out and that specific moment in the muscle itself, because there is no flow, there is no real blood flow inside the muscle because there is is so tight that definitely will see a signal in the NIRS. You're really utilizing oxygen because there is no flow at all. When you relax again, then you can see a, a very fast up slope cause there is a lot of blood coming in with all ion, all the trucks of oxygen are actually coming in and using it.
And that is a specific way of, of training where you can, can see in a way of, if I do this specific 1RM, eight reps Yeah. With 60% of my 1RM Do I show the same graphs going up and down, going up and down. And what you would potentially would see is that, um, if a muscle will change from a physiological perspective that the way you go up again after a maximum contraction that will improve. And that is, that is a good metric of showing that the energy, uh, factories inside your muscle are adapted, are super compensated and are more, easier to utilize oxygen in a very fast way, but also being able to recover very fast and you're then ready for the, the next next rep to do. That's not always, it's not about just doing the reps, it's also and making sure you are recover in that small period of time to do the next rep and the next rep.
10:06 (Kim ter Stege)
Yeah. So you're basically saying that the, the graph of the recovery is almost more important than actually like how much your muscle is contracted?
10:14 (Jeroen Molinger)
10:15 (Kim ter Stege
So you can see how optimized or how well trained your muscle is by seeing how much oxygen flows in again after an exercise?
Training close to failure and setting your own baseline
10:23 (Jeroen Molinger)
Yep. Even, even after, even after one rep. So if you do eight reps, you can even show that when you have the eight reps to go up and down, up and down is how easy is that going up again, going up again and going up again. And you will see that if you really go for the full effort, so that that that eight eight rep on that 70% of 1RM is your, you couldn't do any nine there. The eight is the eight that there's, they must definitely see that there's a, uh, uh, you have a, because of the fatiguing of the muscle, you will see a change of those recovery cycles.
10:56 (Kim ter Stege)
So is there also a way to see how close you are to failure actually because your muscle is not able to recover as fast anymore? Is or is that like too complex?
11:06 (Jeroen Molinger)
No, I think, no, no, I think you can do that, but when you need to do that with the, with your 1RM test, so if you put it then you have to know what is my, how does the graph looks like when 1RM and that's your, that's your, that's your your lowest point, you can go, that's your, your lowest point you can go. Uh, so it's, it's a different way of approaching which exercises where we normally would not have any metric to, to use apart from power potentially when you have a sensor that can measuring your, your speed and your resistance, but with, with with, with a, um, uh, few weights and all or whatever that that is, that is stuff to do and now you have a way of really looking at how does the muscle response on the local level. And that's, that's, that's, uh, that's an interesting approach.
11:53 (Kim ter Stege)
Yeah. So for fitness, a baseline will be the one rep max (1RM) test for different exercises and you can use that to improve your training or to see like for instance, if you train close enough to failure, if you can improve, but also what we talked about the glute and quad dominance, like you can measure that and also difference between muscles left and right. Um, what would be a good baseline for like running or cycling or endurance?
12:21 (Jeroen Molinger)
I think for the cycling, I think the test is mostly done right now, again, going by Pelotons and the ZWIFT now is, uh, is the FTP test. And the thing is when you look when you're doing an FTP test, so you have your critical power being, um, being assessed is that when you then also using that specific sensor, then you know how really low you can go and, and what the normal values would be based on those specific numbers of power that you, that you can, uh, that can put out. Uh, but it is, it is all, I think it is even, even from an exercise or endurance perspective, it's always, you have to have a lot of experience, uh, just using the device. So get yourself familiar with your body itself. So how does your quad or you, and then you have your quad on the, on the top side, your rectus femoris or more on the, uh, on the lateral side, your vastus lateralis or your calf, uh, have some knowledge about when you're putting all those devices into an exercise test, then you have a, a, a potential slope and you see how low you can go and then you do your normal testing or your new exercising, I mean, and to see how does that somehow compare with what I would do.
So it's a zone two, um, endurance, three, four hours kind of training. How does that show in my, in my, uh, values that I see with my NIRS device, uh, from the muscle or if I do a zone two training on the bike, um, but I want to do some hits in between? So I wanna want to do some, some training interval, some some extensive interval training. Uh, what is needed? How low do I need to go to make sure that I'm in the full effort? And if I do four or five sprints, does it show that the muscle is really fatiguing because I'm, I'm changing my recovery's getting worse after each sprint because I'm, I'm, I'm just having too little of recovery. And there was again, the need for a sprint and that itself is showing the potential of the signal in how the muscle will respond.
And if you do that multiple times, you have far more, I think, insight into your cell. You say, Oh wow, I normally would go with the fifth. I would go just in number. Uh, I start off with, uh, 75(%TSI) and I'm now at the lowest point maybe at 30(%TSI), uh, and now I'm not 30(%TSI), I'm not 40(%TSI), so I can maybe give more power. So you can see with the same power, you will not go that low and now you can put on more power with the same way of going all the way down. So you see that the muscle is being, um, compensated for, is able to put out more power with the same usage of oxygen so it becomes more efficient. And that's all what, what literally is, I think it's not about, um, having the biggest and highest power outputs in a VO2. It's all about how efficient are you and how fast can you recover to be ready for the next one.
For who is NIRS a solution?
15:14 (Kim ter Stege)
Okay. So just to have a better understanding, I think NIRS devices like the one from Train.Red are mostly interesting for people that are already sports enthusiasts that are already, um, training for a little while and know a little bit about their body, also about the way of training and then a NIRS device will just give you some more insights on what's really going on inside your muscles.
15:39 (Jeroen Molinger)
Exactly. Yep. Yep. And I think it's, if the test I mentioned, right, the FTP and 1RM is those people that are doing that, are you aware of the reason why they do that test? Right? They want to know, um, the specific maximum values for, for resistance, uh, or for power outputs. And if you just combine those two with those new metrics of NIRS, um, of course it'll be, uh, you need to have a, there's a learning curve here, but I think that can be pretty steep. It's an interesting noninvasive way of just assessing and if you are getting your, to know yourself when you know the training, you know well, how you would respond and how that numbers then show on the muscle level, uh, I think you'll be far more informed in, in how the muscle will respond and, and potentially also in, uh, in competition. We know that thresholds are, are an important way of looking at specific zones. So if you can even do a, when you are decompensating on the, on the muscle level, doing a, doing a, um, a triathlon or marathon or half marathon, you can have a better, better understanding about your how far she can go. Yeah.
16:42 (Kim ter Stege)
Thank you for listening to today's episode. You can find us across all social media @Train.Red. We hope to see you here next time and don't forget to follow this podcast so you don't miss out any of the next episodes. If you're interested in muscle oxygen sensors, the Train.Red FYER, go to our website Train.Red. The link is also in a description.