Why Zone 2 Cardio Is NOT Enough For Elite Combat Conditioning w/ Evan Peikon (SSOF Ep 98)

Evan Peikon1:55

So a really easy way to think about this is if I right now just clamp down on my arm as hard as I can and I'm cutting off my blood flow, and then I release, all of that blood is going to flow back into the limb. And when that blood's flowing, it's going to push against the walls of the large blood vessels, and that's going to stimulate the endothelial cells to release nitric oxide.

Now that form of nitric oxide that's released from the endothelial cells is primarily responsible for lowering blood pressure in bulk blood flow, but it doesn't necessarily help oxygenate the tissues or increase blood flow where we care about as athletes and coaches.

Now the form of nitric oxide that the NNOXX sensor measures, the real technical name for it is S-nitrosohemoglobin or SNO-hemoglobin, which is a little bit of a mouthful, and that's why we just say nitric oxide to be a little bit more concise and elegant. But really what's special about this form of nitric oxide is that it rides on the red blood cells.

So when you have a red blood cell and it comes through the small blood vessels in your muscle, if there's low oxygen levels in that muscle, that red blood cell will release this form of nitric oxide and increase blood flow and oxygen delivery to your muscle tissue.

So the short answer, well why do we care about knowing this? It's that it tells us about our blood flow. And that's really the simplest way to think about the nitric oxide measurement that NNOXX captures. If you see it go up, blood flow is going up. It's going down, blood flow going down. So it's a slightly different way of looking at it.

And then when you combine that with muscle oxygenation, you start to see you get two sides of the coin: how much oxygen is the muscle utilizing, how much blood is being supplied to that muscle. And the combination of those two different measurements gives us really a magical combination that we could use to try and enhance people's performance.

James de Lacey4:09

Okay. So just to wrap this around my head, and probably something the listeners, so the nitric oxide measurement is almost like a proxy for the oxygen that's being delivered of it, and then the muscle oxygenation measurement is the oxygen being used by the muscle. Is that summed up?

Evan Peikon4:36

You said that in a much more elegant way than I did, one sentence. So thank you.

James de Lacey4:36

I'm just trying to make sure it makes sense for myself and the listeners as well, so they're not sitting there being like, "What the hell is all this about?" So you mentioned obviously nitric oxide. So you're saying that nitric oxide supplements, this might be a little bit out of your area but regardless I'm going to ask you anyway, nitric oxide supplements are kind of useless in that regard then because it doesn't improve blood flow to the muscle?

Evan Peikon4:36

I wouldn't say that they're useless, but they may not be doing what people think they do. So a lot of nitric oxide supplements, they improve what we think of as bulk blood flow—so blood flow through the large blood vessels or arteries. Now to the degree if someone is hypertensive and they have high blood pressure, that could actually be rate limiting for their performance. And on that note, taking those kinds of supplements is going to be beneficial for them, the cardiovascular control.

And there are some mechanisms where those kinds of supplements can indirectly increase the form of nitric oxide that we really care about, that increases blood flow to the working muscles. But most of the literature shows that those benefits for performance are primarily in individuals with lower training ages. And as someone gets to a higher and higher fitness level, we tend to see more of a diminishing return for those kinds of supplements, to the point that if we're working with an elite marathon runner, there might not be benefit, or it may be marginal, and then we need to do a little bit of a cost-benefit analysis.

James de Lacey5:55

Nice. What I really like about, I guess, this form of data within conditioning is the idea around... a lot of, I guess, when you first get into this conditioning space or strength and conditioning space for sports, you're looking at heart rate zones, heart rate training. Everyone's on about zone two and high intensity, low intensity. But when you get down to this physiological level, you get a little more granular with how conditioning is prescribed.

So I'd love to just maybe start, let's start really broad, kind of your overview around, or even your thoughts around, prescribing conditioning through this versus a traditional maybe energy system model where someone's looking, hey, we're doing zone two and then we're doing alactic and then we're doing anaerobic, like whatever. Just maybe your thoughts around that, and we can go a little deeper from there.

Evan Peikon6:23

Yeah. So first let's touch on the kind of traditional way of looking at energy systems, and then maybe touch on heart rate zones, and then kind of come back around muscle oxygenation. A lot of times when people learn about energy systems, I think we've all seen those charts that you see in all the different coaching textbooks and manuals. And generally what you see on these charts that I'm thinking of is on the y-axis it shows like a percent energy contribution. On the x-axis you see time, and then there's a bunch of different colored squiggly lines, and each of those squiggles represents a different energy system.

So typically, it's a little bit different in every book, but it will show from zero to 10 seconds it's the anaerobic alactic system powering activity. And then 10 seconds to, let's say, 30 seconds it is the anaerobic lactic system. And then, the glycolytic system, oxidative system, something to that effect. Well, one of the things that's really interesting, really to most people, when they put on a NIRS sensor for the first time...

I had this realization the first time I used a Moxy monitor maybe 10 years ago: you put the device on, you hop on a bike, and you just do a maximal effort sprint, let's say a Wingate, and you just see your oxygen level start plummeting immediately.

The first time I saw this using a Moxy monitor, I was like, "What is this piece of crap? This thing clearly doesn't work if my oxygen level is just hitting rock bottom within eight to 10 seconds." I was like, "This is anaerobic alactic, what's going on?" And then the second thing that you notice is once your oxygen level bottoms out, you're pretty much screwed at that point. There's really not much you're going to do to hang on, and you're just doing what you can to not fall off the pace.

So that's a real kind of eye-opener to most people. And when you start looking into, well, how is this possible, you start realizing that a lot of those traditional bioenergetic models that have made their way into coaching textbooks were our best approximation of how energy systems worked when those models were created. And that was really just due to the technologies that were available to take different physiologic measurements. There was no such thing as NIRS, so we couldn't look at muscle oxygenation. Blood lactate measurements, almost non-existent at that point. Even heart rate was not even in the picture when those models

Were created, and over time as we've had a greater and greater ability to decode different biologic signals, the scientific community has moved past that model. But it hasn't made its way into the strength and conditioning community, and I think this is largely because you could make athletes better with an incorrect view of how the body works. And as a result, there really was no selective pressure to update our thinking.

But this is where now that we can measure these things, I think we're starting to get to the point where new training paradigms do emerge. So for example, if we realize that a sprint is really a test of your maximal rate of oxygen utilization in the muscle and you can be limited by your oxygen supply, now that might lead to some different ways of training a sprinter versus if we say a sprint is a test of anaerobic alactic power. Two different physiologic systems become limiting.

Now, taking a step back and abstracting, you had mentioned heart rate in particular in combat sports. One of the things that's always interesting to me is a lot of times people want to make these dichotomies: heart rate's good, heart rate's bad, blood lactate's good or bad. And I think heart rate has had a lot of value, but there's also some limitations, and I think something like combat sports really exposes the limitations of a heart rate measurement.

Because when you have someone, whether you're wrestling, doing Brazilian jiu-jitsu, or striking, if someone's about to throw a punch at you, what are you going to do? You're going to brace. When you brace, you're going to increase your intra-abdominal pressure, and if you're measuring your heart rate, what's going to happen? It might go from 160 to 180 in a few seconds.

Does that mean you just jumped from a zone three to a zone five and now you're at a different physiological limitation? Probably not. What it says is that your heart rate rapidly increased. We don't really need to look much more into it than that.

So I think where muscle oxygenation becomes a really valuable metric for guiding training intensity is that the measurement is captured in the local working muscle. So when we see that you're deoxygenating your muscles, we know that it's an increase in metabolism, it's an increase in intensity in the amount of strain on the muscles, and it's not going to be affected by things like changes in blood pressure from bracing, having too much caffeine before your workout, not eating as much, being a little bit dehydrated, being fatigued.

These are all things that are going to influence your heart rate measurements day to day and will shift zones one way or the other, and they don't impact muscle oxygenation to the same degree.

James de Lacey11:24

Nice. And just a clarify as well around you mentioned obviously the 10-second sprint, you see muscle oxygenation just plummet on there. And just for the listeners just to try bring back, so when we're talking anaerobic alactic, you're typically talking without oxygen. So in theory, if these energy system models were as they were, you shouldn't see that big drop in muscle oxygenation, whereas you do see it, which means that oxygen is being used, which means it can't be purely alactic anaerobic in that sense.

Evan Peikon11:51

And this is where I think we all got a little off track with terminology, because even saying anaerobic alactic, we break that word down: anaerobic without oxygen, alactic without lactate. You're never going to have a scenario in the body where there is not oxygen or there is not lactate present.

So even if we were to just change the word and say oxygen independent or lactate independent, it doesn't say that those molecules aren't there. It's just saying that certain energetic processes do not use oxygen or lactate, but they're all happening at the same time regardless.

So if you were to have someone do a maximal effort sprint and you have their muscle oxygenation level decreasing, their phosphocreatine stores are decreasing at the same time. When they're recovering, both phosphocreatine and oxygen are recovering.

So instead of thinking of all the different energy systems working in these isolated compartments, everything's going on at the same time to varying different degrees. And the only real time that you're relying on anaerobic metabolism, or oxygen independent metabolism to a very high degree, is when you've essentially tapped out your oxygen stores in your muscle, and that's the point where you're just struggling to hang on, because oxygen independent energy production is incredibly inefficient.

So once you've got to that point, you're pretty much done already, versus this traditional view where it's like that's your power at the beginning of a sprint and then you start relying on the oxidative system. It's almost more of a flip-flopped inverse.

James de Lacey13:28

[inaudible] have much of an impact, but regardless you're going to correct me on that if I'm wrong. But regarding the actual measurements of muscle oxygenation and nitric oxide, how are you able to differentiate what is the limiting factor in someone's conditioning?

Evan Peikon13:28

Yeah, totally. So first, touching on what the limiters are, so when I'm thinking of physiological limiters, what I'm really thinking about is the rate limiting factor for improving someone's VO2 max. So one way that we could think about VO2 is it's the maximum integrated capacity of your respiratory system to uptake oxygen, your cardiovascular system to get that oxygen to your muscles, then your muscular system to use that oxygen.

So we're talking about improving someone's limiter. We're saying one of those three processes is slower than the others and we want to improve that to improve someone's VO2 max and hopefully their performance depending on the sport. But we could get into in a little bit why that might not always be the case in combat sports in particular.

So the way that we could use something like NNOXX to identify which one of those systems is the limiting factor is by putting someone through a traditional ramp incremental exercise test, which you would typically see done to try and find someone's VO2 max.

So when we're putting someone through one of these tests, what we're looking for is how their different biomarkers change over time. So generally what I would do is have a step test, could be three-minute steps, five-minute steps, let's just say four for the sake of this conversation. So we'll have someone do four minutes at a very low intensity, and then every four minutes after that we'll increase their power output by a fixed increment until this person reaches volitional failure.

So the only thing we know going into this is their intensity is progressively increasing, and at some point they're going to be using a power output that's unsustainable.

The first thing that I want to look at is what does their muscle oxygenation level look like while they're doing this. Before we had said we touched on muscle oxygenation, but I never properly defined it. So this is the oxygen saturation level in the working muscle. At rest you're generally going to see this sitting maybe 55 to 75% depending on the person, and at volitional failure it could be anywhere from 10% up to 40 or 50% depending on how fit someone is. The fitter you are, the lower it will get.

So what I want to see is when someone transitions from a sustainable intensity to an unsustainable intensity, what happens? Well, if someone is limited by their ability to utilize oxygen in the working muscle, we effectively see that nothing really happens to that measurement. Their oxygen level is fairly high in the muscle, and then it becomes unsustainable and it is still high in the muscle, and that's because they cannot utilize oxygen in their muscle effectively.

Off the bat I would say that person has an oxygen utilization limitation. All other things considered, if they don't address that, they're probably not going to make that many meaningful changes to their performance.

Now let's take a different scenario: we go from a sustainable to an unsustainable and muscle oxygenation just completely plummets. Now we at least know we have an oxygen supply limitation. The question is, is that a respiratory limitation or is it a cardiovascular limitation?

This is where having the nitric oxide measurement that NNOXX provides gives us some extra granularity. So what I want to see is what happens to this NO measurement. Let's take a first scenario: you're progressively increasing intensity and that NO measurement is slowly going upwards, we're increasing blood flow to the muscle. But let's say you get to about 80, 85% of someone's max heart rate, and then from there out in the rest of the test their nitric oxide level does not move. They're continuing to use more oxygen in the muscle and that nitric oxide level's just plateaued. That would indicate that someone has a cardiovascular limitation.

Now if someone has a progressively increasing nitric oxide level up to the point of failure, that would get us to start thinking it's probably a respiratory limitation. That alone covers, let's say, 80% of assessments.

Sometimes it's not so clear-cut though, and this is where we often recommend bringing some additional pieces of data into the picture. So heart rate alone, that could add a lot of granularity. With those cardiovascular limited athletes, they typically see a plateau in their heart rate leading up to voluntary exhaustion. Respiratory limited athletes, it keeps ticking upward indefinitely.

Could also get blood oxygenation. I'd say for most people, blood oxygenation that you would get on a pulse oximeter, most people are familiar with seeing it on an Apple Watch or WHOOP, ordinarily a completely useless metric for performance testing, because in the vast majority of circumstances it doesn't change at all during exercise. You'll start a session, you'll see it around 97, 98%, push yourself to failure, still probably going to be at the same point.

With the exception of respiratory limitations in elite endurance athletes. I specifically mention elite because there's a phenomenon called a pulmonary diffusion limitation, which essentially means that your cardiac output and stroke volume are so high that your red blood cells move so fast through the capillaries in your lungs that...

They don't pick up oxygen. So in those really elite endurance athletes, you'll often see their peripheral oxygenation or blood oxygenation dropping by like 20%. And one of the signs that this is happening is sometimes you'll see these athletes, their lips will turn blue if they were to do some kind of like max effort assessment or VO2 max test. And usually they'll say, "My fingers or toes are numb," or, "My whole entire arm went numb." I've seen that one a few times.

And then from there you could just keep getting more and more nuanced. You could do spirometry, you could start getting gas analysis, or you could even just think about what are some of the trends that we see in these athletes.

In the utilization limitation, these are the ones that often don't make sense to very experienced trainees. This is the athlete that you might say, "What's your one rep max back squat?" and they might say, "100 kilos." And then you're like, "What's your five rep max back squat?" And they're like, "99 kilos." "What's your 10 rep max?" And they're like, "96 kilos." And you're like, "You do realize that those are all the same weight?"

And similarly, I worked with an ultramarathon runner, this was years back. He had raced like 200 milers and he wanted to start competing in half marathons. So we're like, "Sweet." He ran a half marathon just to get a feeler, and I looked and I was like, "Your 100 mile pace is the same pace as your half marathon pace. I think we have a little bit of an issue there with your utilization."

On the flip side, the delivery limited athletes are the ones that are almost the complete opposite. You're like, "What's your one rep max back squat?" "200 kilos." "What's your five rep max?" "150 kilos." And you're like, "That is a massive difference." And the respiratory tend to be a little bit more balanced, kind of like the normal average profile that most people are used to seeing.

James de Lacey20:40

I hope you're enjoying the chat so far. Before we get back to that, I just want to let you know that Sweet Science of Fighting is more than just a podcast. We have a full training app with strength conditioning programs for strikers, grapplers, and MMA athletes, so you don't have to think about what you're doing and you're getting access to the latest scientific methods to improve combat sports performance.

We have programs specifically for judo, for jiu-jitsu, for wrestling, MMA, boxing, Muay Thai is coming soon. All these things are going to be in the training app. We also have a private community where some of the coaches that have been on the podcast are in there to help you with any training questions and any performance questions you have. For example, Andrew Asser and Casper Devit.

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So what are you waiting for? Jump down the description, you can check out the Sweet Science of Fighting Underground. Otherwise enjoy the podcast.

I want to start with the VO2 max. And we'll go into some of the training, some of these different problems. But obviously you mentioned with some of the problems with VO2 max. My understanding is VO2 max is mainly limited centrally, so from a delivery aspect. So maybe you can just touch on that if I'm wrong or right.

And also, obviously we know that VO2 max doesn't predict endurance performance. So are you looking, is VO2 max kind of like the goal setting you're trying to improve when you're looking to improve some of these, or is that kind of just a way for you to be able to prescribe or be able to attack some of these limiting factors?

Evan Peikon22:25

Yeah, yeah. So let's kind of start at the beginning. So one, yeah, traditionally the research would say that VO2 max is limited by central factors. The really interesting thing is when you start looking at papers, they make that statement and then they cite another paper. And you follow that breadcrumb trail back and you realize that actually comes from – I'm blanking on the name right now, this will come back to me later – we'll come back to that, in 1921, establishing the concept of VO2 max.

And in that paper, keep in mind when they used to measure VO2 max, it was kind of wild. Right now we have metabolic analyzers and it's very fancy. They literally used to have a giant inflated sheep stomach and you would breathe into this giant stomach bag and they would actually measure the volume of gases, which is absolutely bizarre.

But anyway, during that time, the Nobel Prize was awarded for coming up with this concept of VO2 max. And essentially what that concept says is if you progressively increase exercise intensity, whole body oxygen consumption increases, but up to a certain point of intensity, additional increases do not elicit greater increases in oxygen consumption.

They then did some back of the napkin math to calculate what they expected venous oxygen concentrations to be and what they expected arterial oxygen concentrations to be. And then they worked out the math of what is stroke volume doing, what is heart rate, and they came to the conclusion that VO2 max must be limited centrally.

Now the interesting thing about this concept is that they didn't have the ability to measure almost any of those factors that they were working with. So in those initial back of the napkin calculations, they approximated that baseline oxygen concentration in muscle would be about 60 to 70%. They absolutely nailed it on that. They then said that at volitional exercise failure it should be around 10%.

Now if we were to take that to be true, essentially when you calculate VO2 max using the Fick equation, it's the arterial venous oxygen concentration difference. So the difference between arterial blood and venous blood, and then you multiply that by stroke volume. Well, if we're assuming that everyone's starting at around the same arterial oxygen saturation, which is likely true, and that everyone's finishing at roughly that same venous oxygen concentration of 10%, then the only way that you could get your VO2 max higher is to improve your cardiac output.

Now the problem is, is that because they did not measure venous concentration, they didn't realize how variable that is. So until people started doing testing with technologies like NIRS – and we're talking in like the '80s, early 2000s, when it's really getting into sport science – we realized how variable that is. Not everyone is reaching that 10% muscle oxygen saturation. In fact, some people's hardly change.

So it becomes fairly clear that muscular limitation can exist. It also started to become a little bit more clear that you could have a respiratory limitation when they started doing work on elite endurance athletes and seeing that that pulmonary diffusion limitation exists. So it's kind of like this case of path dependence, where the original work on VO2 max said that it's limited centrally, and then that kind of got repeated for the next 104 years, even though there's very clear evidence in the literature suggesting otherwise.

Now in terms of how that relates to performance, I'm totally with you. VO2 max is not a very good measure of performance within a group of like-minded people. So if we were to take 10,000 people in the population and we had all of their VO2 maxes, we could pretty accurately predict where someone's relative fitness is. If your VO2 max is 75 milliliters per kilo per minute, another person is 45, you're going to dust that person on any event that you do – a 2K row, a 5K row, you name it.

But within a group of people with similar VO2 maxes, it actually becomes a very weak predictor of performance. That's because it's just one of many factors that influence performance. So the way that I think of VO2 max is it's just an upper ceiling of how much oxygen could your whole body consume, how well could you uptake it, transport it, utilize it.

Now there's a second ceiling, which is all the different sport specific competencies, which differ sport to sport. So for example, if you have a fighter, let's say they come from a triathlon background, their VO2 max is like Olympic caliber, and they come into combat sports and you realize this person cannot strike, they don't know how to grapple, they don't know how to block punches. Doesn't really matter that their VO2 max is 75, they're not going to do very well.

But on the flip side, let's say you have someone that they're incredibly experienced, they've been doing Brazilian jiu-jitsu since they were literally an infant and they're extremely efficient, but they've never done conditioning and it's very low. Those are two very different scenarios. That first person, their conditioning is through the roof, they need to improve their sport specific competencies. But for that second person, they will get to a point that their conditioning is limiting their ability to get to the sport.

So in addition to thinking of physiological limiters, we now have a secondary concept of sport specific limiters. And there's a connection between these two different things. So it's both, does this person need to improve the sport, do they need to improve their physiology, some combination of the two? Then within each of those categories, what do they need to improve in the sport, what are the rate limiting aspects of their physiology?

And that's the art of coaching, kind of working back from there to figure out how do you find those things, how do you develop them, how do you fit it all together in a training program?

James de Lacey27:55

Can a sport

Can a sport be more peripherally or muscularly demanding in terms of some of these rate-limiting factors? So as an example, grappling, obviously you have more isometric style contractions holding, striking more kind of velocity based in terms of throwing punches and things like that. Does that influence at all then how the conditioning looks, regardless of what's showing up maybe on some of these measurements?

Evan Peikon28:49

I'd make the argument, yes, different sports are going to select for different types of physiologies, and to that extent you need to train for that sport. So for example, endurance sports select for people with respiratory limitations, power sports select for people with cardiovascular limitations. So you always need to think about what is the relevant physiologic characteristics that we need to build up for a sport, then what is the individual's physiology, and how do we work that person towards the optimal physiology for the task.

Combat sports are obviously a little interesting in that, what are the physiologic demands of combat sports? Well, it's probably going to depend on the style of fight, who your competitor is. Then it adds another layer of strategy on. So I mean, that's your job to figure out. I'm just here to run my mouth a little bit.

James de Lacey29:22

Fair enough, fair enough. Yeah, it's interesting because I've got headlights of Andrew Asher on the podcast, Ed Baker. Both of them believe through some of their stuff combat sports is potentially more peripherally I guess demanding than centrally demanding. So potentially they're targeting peripheral adaptations could be potentially better.

I want to dive down that road as well now anyway, in terms of training methods for some of these. So someone who may have a utilization or peripheral limitation, a delivery or heart blood pumping limitation, or respiratory or essentially breathing limitation, how do you attack each of those? And are you trying to attack them say independently? Is all your training geared towards that thing if that's a limiting factor, or you kind of still doing a broad scope of training?

Evan Peikon30:22

I would say the training is prioritized towards that limiting factor, but we always need to train these other systems. One, we can never really isolate anything entirely. It's more biasing training. But secondary to that, if you're really pushing yourself, you're not going to stop when your limiter can't cope with the stress anymore. If you're in a combat sport and you're respiratory limited and you can't breathe anymore and your respiratory muscles are fatiguing, you're not going to say like, "Hey, could we chill for like three minutes? I just overloaded my respiratory system and I need to kind of get back to baseline before we go forward."

So anytime you push your limiter to its max, you're going to start relying on all the different compensation mechanisms. So it's like your limiter is your plan A, but you still need to plan B, C, D, E, and F. And that's where we want to make sure that the systems that you rely on when your limiter gives out are also going to be strong.

James de Lacey31:13

Gotcha. And oh wait, you have a comment in the chat before I carry on. "Fighting is not aerobic. Recovery is aerobic. Fighting is an anaerobic event that occurs in an aerobic environment." I don't know if you have anything to say to that, but—

Evan Peikon31:13

What was the— so he's saying fighting is not aerobic, recovery is aerobic, fighting is an anaerobic event that occurs in an aerobic environment?

I'd say if fighting is an anaerobic event, if you're holding your breath for the entire time, that's probably true. But going back to the original point, you were never not going to be using aerobic metabolism. If you throw a punch, we're talking about milliseconds—oxygen is going to be utilized. If you deplete the oxygen in your muscles, you are not going to be throwing that punch effectively. So there's really, again, never going to be an anaerobic sport.

James de Lacey32:12

I'm going to come to your question in a second, but before, I want to jump down—let's go into some specifics now. Someone who's trying to target these central delivery adaptations, maybe just some examples of sessions, a session would look like there, and then we'll jump into utilization and the respiratory stuff.

Evan Peikon32:12

Yeah, totally. So when most people do interval training, we tend to think of fixed pace intervals. So let's say you're doing a 500 meter row at a 1:45 pace and you're just holding the same pace across. Now when we're trying to target different physiological limitations, we want to be creative with how we manipulate the intra-interval pacing structures.

So for someone with the delivery limitation, we're generally use gradual ramping structures, so starting the interval easy and progressively picking up speed. Most people are familiar with something like a tempo run—you're effectively doing that over let's say a 30 minute period. This is going to be doing that over let's say a two to five minute period if we're talking about a shorter duration sport.

Now the reason that we're doing this is that when you deoxygenate a muscle, there's going to be a release of nitric oxide to increase blood flow. Now anytime you increase your blood vessel size, your heart's going to have to pump harder and faster to maintain your blood pressure—otherwise you black out. Thing about athletes with the cardiovascular limitations is that you need to gradually put them in a scenario where their heart could pump harder and faster and cope with that demand without getting their sympathetic nervous system to try and restrict blood flow to the muscles.

So generally what this means is starting relatively easy and picking up speed. If we were to go back to that 500 meter row at a 1:45 pace fixed speed, instead we might do a 100 meter row at a 1:55, 1:50, 1:45, 1:40, 1:35 pace. The average speed for that 500 meter row is exactly the same in those two scenarios, but it's a different physiological adaptation.

Now if you want to get a respiratory limited athlete, you'd almost entirely flip-flop that. Because for a respiratory limited athlete, you want to spend as much time as possible close to their VO2 peak. If you were to do that traditional 500 meter row at the 1:45 pace, anytime you do intervals like that, the first four hundred meters are easy. The last hundred—home stretch—is when you're starting to really push yourself, and that's when you're getting close to your VO2 peak.

So for the respiratory limited athlete with the traditional interval training structure, it's a very small percentage of that that is actually pushing the respiratory system to a near max and stimulating that system to the degree that's necessary. So if you flip-flop the pace and you were to say, "We're going to start really fast and progressively decrease your speed across the interval," what you're going to do is get them to a VO2 peak very quickly.

And by progressively decreasing their speed, they could maintain that very high level of oxygen consumption without having to tap out. And then a very high percentage of that interval is actually going to be targeting their limiter.

Then the utilization limited athlete's a little bit simpler in that that person probably has some combination of poor muscle recruitment, so they need to do strength training, low mitochondrial density in the tissue, so things like repeat sprints. Or they might just be coming back from an injury, which in that case they need to actually rehab in order to start regrowing blood vessels and getting the mitochondrial density to utilize oxygen in the muscle.

James de Lacey35:30

So when you're saying decrease or increase the speed across the interval, you're talking about within the 500 meter interval, not 500 meters at this then 500 meters at that?

Evan Peikon35:30

Yeah, yeah. So within each individual interval, actually manipulating the speed across the interval, and then doing multiple sets of that.

James de Lacey35:30

Okay, so you'd be starting for example at a 1:50 pace and then you'll be—I don't know, after how many times do you change? You're going 100 meters, 1:50, 100 meters, 1:45, kind of thing?

Evan Peikon35:57

Yeah, you could do it at every 100 meters. You could go 100 meters at 1:50, 1:45, 1:40, 1:35, 1:30, or you could do it a little bit more subjective. So if you were doing a 1K row, you could say, "I want you to start your 1K at a 1:50 pace and finish it at a 1:40 pace." Okay, try and do that at a pretty linear increase across. You could kind of play around with that a little bit.

You could do longer duration intervals like that as well. When I've worked with some competitive cyclists, we might do 20 to 30 minute intervals like that. We might have them do six half-hour intervals increasing speed across, which sounds like a lot of work. But when you're racing for plus hour distances, that's going to be necessary for them.

James de Lacey36:51

So how do you know what speed to start and finish it as? Is that a trial and error thing or is there some test someone can do?

Evan Peikon36:51

Yeah, so originally I used to work for a company called Training Think Tank, and we worked with a lot of top CrossFit competitors. And when we first started working with these protocols, we were using muscle oxygenation. So we were saying, working with these different athletes, "I want them to start at their baseline muscle oxygenation, let's say 65%, and I want to bring them down to their minimum level at the end, whatever that minimum is—it's 15, 25, you name it." And then we'd kind of work back and say, "Well, what pace do we need them to start to be able to stay relatively baseline, and what would be a good finishing pace to get lower?" And we'd kind of work backward from there.

So we ended up coming up with these kind of easy heuristics for people.

So if you were doing 500 meter row repeats, you would take your 2K PR pace. So if you have a 7 minute 2K, that's a 1:45 split. That would be the middle of that 500 meter. So you would start 100 meters 10 seconds slower than your 2K, 5 seconds slower than your 2K pace, then the middle 100 meter would be at 2K pace, then 5 seconds faster, 10 seconds faster. That ended up being a really good heuristic.

So depending on the protocol, we just had nice easy ways for people to do it to start out with. And if someone were to find, if they're very delivery limited, that might be brutal for them and they need to pull back the paces. Or they might find that that's a little bit too easy and they need to increase the intensity. But it's a good start there, address as needed.

James de Lacey38:07

So where does Zone 2 cardio fit into this paradigm? Because obviously that's still very popular in terms of what people are pushing. Well, maybe start with where does that fit, and then are the adaptations essentially the same, similar, or different?

Evan Peikon38:32

Yeah, so for Zone 2 we're going to be looking at a few different things. One is going to be the central adaptations, things like improving someone's cardiac output. And then there's also all sorts of peripheral adaptations that we're looking for: increased like VEGF expression for blood vessel growth, improved muscle metabolism.

So I'd say I generally think of Zone 2 as something that is going to be supportive work for a delivery limited athlete or someone with those cardiovascular limitations. But the way that I think about Zone 2 is that it's necessary but not sufficient for people with that limitation.

So I would kind of reframe it like, imagine you had someone that wanted to improve their one rep max back squat. Generally we're going to want them to squat heavy. You might also want them to do some leg extensions, leg curls, calf training, lower back training. Zone 2 would be the equivalent of those assistance exercises. It's an important part of the picture, but not the only thing.

So it's the same for a delivery limitation. Zone 2 is effectively the assistance work for the cardiovascular system or the more developmental work that's really going to help move the needle. That's going to be things like those gradual desaturation intervals that are a little bit more compressed. You're actually pushing people to near maximal cardiac output.

James de Lacey39:57

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So check that, that'll also be down in the description with a discount code. But back to the podcast.

You talked about repeat sprint intervals and a few other things. Maybe dive into what a repeat sprint interval session might look like for a delivery limited athlete.

Evan Peikon40:53

Sorry, for utilization—I said delivery, that's completely wrong—utilization limited athletes. So yeah, what we're really trying to do with the repeat interval is have this individual work at a near maximal rate of oxygen utilization, and over time we want that to improve.

So generally I tend to stick to very short sprints, sub-12 seconds, with sufficient rest to reoxygenate their muscles. A lot of times we'll auto-regulate this. And let's say I'd put a NIRS sensor on someone's quadricep, and I like to start with this version because I work with a lot of CrossFitters. Let's take the Echo Bike. We know someone's maximal sprint power output on the Echo Bike. We'd say, let's have you do a 10-second sprint at 75% of your maximal power output and rest until you re-oxygenate the tissue fully.

So what you would see is they sprint, the oxygen level in the tissue goes down a bit, and then they recover up to a baseline. And then I would say you're going to keep doing this until one of three things happens. Either you cannot deoxygenate your muscle down to the same degree as previous sets, and that would tell us either they're just fatigued or they're changing their muscle recruitment pattern, but something's going on where they're not getting the adaptation that we want anymore.

The second strike would be you're not re-oxygenating the tissue back up to the previous sets—i.e., they literally cannot recover their oxygen level back up to baseline. Or their biomechanics are just going out the window to where it's not productive for them, they're at risk of injuring themselves. You could technically add a fourth constraint and say if you can't hit your power output anymore. But typically if one of those other three things are happening, they're probably not hitting the power output that's prescribed anymore.

Then over time what I would do is I'll typically put a 45-minute running clock on this kind of workout. I'll say another constraint is if you hit 45 minutes and you've already done 30 sets of sprints at that point, let's shut it down there. Next time we'll increase your power output. So if someone's ending this workout in 15 minutes, 25 minutes, I'll just say we're just going to keep doing this over and over again and we're going to see if you could get more sets over time. Generally you do see them progress, and once they hit that cap, you increase the power output.

Now if someone plateaus after, let's say, three or four weeks at a given power output and their sets are still pretty low, that's where I might start employing other things like true maximal effort sprinting in their training, assuming they're not injured or they're sufficiently strong. And then that will often move the needle again.

So a lot of times when we're working with these limiters, I really don't plan that far ahead. I just say, what do we think is a good protocol for the limiter? Could we collect some data, confirm that? And we'll just keep doing the same thing while you're progressing. And once you stop progressing, we'll come up with the hypothesis: what do we think you need next? Does it move the needle or not? And just keep rinsing and repeating that cycle.

James de Lacey43:56

So with the muscle oxygenation, coming back near to the beginning, it's almost like a near or complete rest period then between each interval?

Evan Peikon43:56

Yes, it will be a complete rest. I'd have them do the sprint and yeah, just sit there and hang out on the bike until you fully re-oxygenate the tissue. If someone is really fit, you might see this happening in 40, 50, 60 seconds. Someone's lower fitness, this might take 90 seconds or so. Over time you do want to see it becoming shorter and shorter. I mean, the quicker you could fully re-oxygenate after maximum effort sprint, the better.

So there's going to be some individual variability there. But if someone wanted to try this kind of protocol at home and they don't have a sensor, I would say 60 to 75 seconds is probably a pretty good starting point for most people.

James de Lacey44:51

Could someone use heart rate? I know that's being used a lot with, hey, go again when you're at 120, 130 beats per minute. Is that enough if you don't have a sensor?

Evan Peikon44:51

I'd say for this type of training, if someone didn't have a NIRS sensor, I would probably have them use subjective perception for their power output versus heart rate. Just because it's not really going to be enough time for heart rate to elevate. And a lot of the changes in heart rate that you'll see in a 10-second sprint are from increased intra-abdominal pressure, because you're really generating a lot of power.

So then those drops in heart rate after the interval might not actually be reflective of oxygen delivery to tissue, it might just be blood pressure stabilizing.

James de Lacey45:16

Okay, that makes sense. I'm going to come just to a question in the YouTube chat, then we'll come back to this. But he's asking, he's coming to the mats from a long pause because of injury. He has three to four intensive sessions on the mat, so I'm assuming it's just jiu-jitsu, three to four hard jiu-jitsu sessions where he's literally catching his breath often. Should he put some extra conditioning or just keep struggling?

Evan Peikon45:44

Yeah, I'd say it's, I can't speak to the jiu-jitsu specific training because whoever this is is absolutely more knowledgeable than I am. But I would say, you're just coming back to the mat. If after two or three weeks you're finding you're still struggling and you're not seeing any meaningful improvement, that's when I probably would look to incorporate some other kind of conditioning into your training to move that needle. But if you're finding that with the sport-specific work alone your conditioning is coming back on its own, I mean, you might be good to go.

The one thing that I'd be curious about is what kind of injury. Keep in mind, not a doctor, don't play one on the internet, but the things that I'd be thinking is if you did have some kind of muscle or tendon tear, what most people don't always think about is that when we tear a muscle or tendon, we also tear our blood vessels. It's going to take a little while for blood flow to those tissues to start improving.

So if you were in that kind of scenario, obviously talk to your doctor, but I'd probably ask them like, would doing some kind of low to moderate intensity conditioning maybe help those systems come back online quicker? And to the extent that they will, it's probably going to help you in your sport.

James de Lacey46:57

Looks like it was an ACL injury and it's judo, not jiu-jitsu, but regardless, I think everything he said there kind of applies to what's going on. So yeah, if you have the time, a little some extra conditioning may help. Obviously, ACL injury is usually a long layoff as well, so if you weren't doing much during the injury then yeah, you might have a little bit of catching up to do.

But I want to come back as well to this idea of this utilization limited athlete you're doing kind of like almost sprint to sprint intervals with full oxygenation recovery in the muscle. Is there a time and place where you're using incomplete recoveries? So a lot of people, I think, when they're doing intervals without any kind of measurements, they're doing kind of hard sets, short rest, and they're just kind of repeating these over and over. That's kind of like the go-to for most combat athletes who are just kind of doing work. Is there a time and place that you're using those?

Evan Peikon47:50

Yes. I'd say yes, but not when we're specifically trying to improve someone's utilization. Because if someone is utilization limited, we don't necessarily want to be starting to stress their respiratory or pulmonary system. We really want to make sure that they are, same thing where if someone is training for maximal strength, that they are nearly fully recovered between sets. Because we're trying to essentially get the biggest delta, so the greatest change between oxygen at baseline and at the end of the interval.

So if your oxygen is here at the end of the interval and you're recovering it back to here versus all the way up here, you're going to have a shorter change on each interval. We want the greatest change there.

Now keep in mind, when someone has a utilization limitation, as they kind of work their way out of that utilization limitation, they tend to become respiratory limited, which, you know, there's a whole physiological explanation we don't need to get into. So what I'll typically do is as someone works out of that utilization limitation, I would want to start stressing their respiratory system more, knowing that they're just going to develop a respiratory limitation at some point.

And that's when I would start adding things like those incomplete recovery intervals into their sprint training, so they could start creating a little bit more of a pulmonary system stress mixed with the muscular stress. So it's kind of like a nice transition protocol.

James de Lacey49:13

And you could also do what you mentioned earlier around starting your, for example, those 500 meter intervals faster—say at the minute 30—and then progressing to the minute 50 by the end, doing the reverse, right?

Okay, perfect. And then most people don't have access to a NIRS device or able to interpret any of the data. Are there any field tests that could give someone just a proxy or an indication of maybe if they're delivery or utilization limited?

Evan Peikon49:41

Yes. I'd say the first thing, which is by far the easiest, is those kind of different heuristics that we talked about earlier. So, you know, are you that athlete that's kind of fixed gear, whether you're running an 800 meter or a mile or 5K, you're kind of holding the same pace on all of them?

A lot of times these athletes who are utilization limited, I should probably mention, are often the ones where if you were to say, go row a 2K as hard as you can, and they finish and you're like, what stopped you from going fast? And they're like, I just couldn't pull any harder, but it's not that I couldn't breathe, it's not that my muscles were burning. I just can't go any faster. That's probably a sign that you're utilization limited.

If you're the athlete who is the opposite, you tend to have a lot of top-end speed and power but poor endurance relative to that, that is generally going to be a sign of a delivery limitation. Another sign, and you do see this in combat sport athletes sometimes, is someone who gets pumped out a lot, where they're like, I was grappling, my biceps and my forearms were so full of blood and pumped that I just couldn't keep holding on to someone. That's going to be another sign of a delivery limitation.

Where that respiratory limited athlete is going to be a little bit of a mix between the two, so they tend to have a little bit more of a balanced speed and speed endurance profile, or strength and strength endurance. And when you push them to their max, they're going to be the ones who tend to get the numbness in the fingers and toes, the blue lips.

But, you know, if you're a respiratory limited athlete and you're in combat sports, you're probably never going to get pushed hard enough on your conditioning that you are going to reach those true physiological limitations. But those are the really easy ways to kind of ballpark people.

Secondary to that, you could do what's called speed preservation testing, which is a little bit more of a pain to do. But essentially the way this works is if you were to do it on a rower, you would get someone's 1K, 2K, 3K, 5K PR paces, and you would essentially start to look at ratios between those to see what percentage of your speed at 1K are you preserving for a 2K, a 3K, a 5K.

And you'd start to be able to graph out these different avatars and get a feel for what you are. But that's a little bit more of a technical way to do it. You kind of end up in the same place as just giving people heuristics.

James de Lacey52:12

If you're a hardcore data junky or some biohackers listening or something who want to test everything, I'm sure they—

Evan Peikon52:12

Yeah, fellow data science, hit me up. I could send you calculators to do that. But otherwise, I think those heuristics are a good ballpark if you don't want to invest in the technology or you don't feel you have the time to get into that.

James de Lacey52:35

Yeah, send me those calculators, I'll put them in the description for everyone as well. But have a question from Andrew Aser here in the chat, and I think you answered actually part as part of that. But he's saying, is respiratory really a limitation in some combat athletes? It's tough in comparison to peripheral. And he's saying when you look at, say, linear changes and desaturation and resaturation in relation to heart rate kinetics and VO2, I don't know if you've got any comments on that.

Evan Peikon53:00

Yes. I don't think combat sport athletes can be respiratory limited, but I do not think that that's going to be their sport-specific limitation. So what I mean by that is you're probably not going to expose a respiratory limitation in a combat sport. You will probably have some other form of limitation.

In the same way that, generally, if we were to say my respiratory system is what limits my VO2 max from being higher, if I go and do a 100 meter sprint, I'm not going to expose a respiratory limitation. I'm probably going to end up having a muscular limitation. So it's that difference between gross physiological limitations and sport-specific limiters. I mean, I agree with Andrew there. I don't think you're going to expose a respiratory issue in a fighter unless they have COPD or something, and they probably shouldn't be fighting.

James de Lacey53:28

Fair enough. So with all this work you're doing, research you're doing, and all the things you're applying, do you—would you say throw away the heart rate monitor?

Evan Peikon53:57

I wouldn't say throw it out. I would say be a little bit more skeptical of it. So just, with any tool you use—muscle oxygenation included—it's just important to know what the limitations are, what is the measurement good and not as good for, how does it relate to other data points.

So I do still see value in heart rate monitoring, but I think we just need to acknowledge where is it going to be limited. If you're using it as a combat sport athlete, if it's really hot in the gym that day, you're getting cardiac drift. Does that mean that you just went from zone 2 to zone 3 because your heart rate went higher, or does it just mean that you're pushing more blood through your circulation to your skin for cooling?

If you're bracing and you're increasing your blood pressure and your heart rate spikes up, again, is that indicative of changes in muscle metabolism, or is it just a reflex response? So I think as long as we could acknowledge those things, it's still a good instrument. I still use heart rate monitoring myself. It's just that I like to cross-reference it against other data points that might have some different limitations, and between the two, you could kind of come to a better conclusion.

James de Lacey54:48

No, Andrew's commented here. He says he thinks people don't understand heart rate kinetics and fast and slow phases, and hence heart—

Evan Peikon55:17

Rate monitors not used well. I've seen some of Andrew's graphs—he's done something for me as well. They're confusing with this body data science background and his body algorithms that he's created. He's going to come back on at some point to maybe explain some of that. He's trapped in the world of zones rather than kinetics against other data points.

Yeah, I think we've talked about zones as well. I think even you share a similar philosophy there around heart rate zones might not tell you too much.

James de Lacey55:17

Yep, absolutely. And yeah, I might add to that if my data science skills could start approaching Andrew's, that would be a very happy man as well.

Evan Peikon55:40

Yeah, he's just a massive nerd. Just boxing and computer together now. Perfect.

James de Lacey55:40

I think that's all the questions I had for you, Evan. Is there anything else you wanted to add to that, and if not, where can people find and follow you?

Evan Peikon55:40

So I don't think I have anything else in particular to add, but yeah, you could follow me on social media. I'm primarily on Instagram and Substack, just my name, Evan Peikon. And then for anything related to Nnoxx, you could find us on every social media platform. It's Nnoxx, N-N-O-X-X underscore Inc, on literally every social media platform. So that would be the best way to find out about that technology.

James de Lacey56:05

Perfect. And give Evan a follow on Instagram. I'll link in the description. He's got a lot of the stuff we talked about in this podcast—he's got various Instagram posts about and graphs showing exactly what we're talking about too, so you can kind of see a visualization of what he's doing.

Actually, I do have one more question before we sign off around breathing. So I just saw your Instagram now around breathing and performance. Do me just give a little overview on—I mean I'm just going to give a start very general—just an overview on breathing for performance regarding your muscle oxygenation and nitric oxide graphs.

Evan Peikon56:53

Yes, so recently I've been playing around more with seeing how different breathing protocols impact nitric oxide levels as we would measure them in muscle tissue. And what I'll say is we've gotten a lot of interesting data. I'm not at the point where I could tell you what the practicality or usefulness of this data is, but it's more so that a lot of times you see Wim Hof protocols, box breathing, apnea breathing—people talk about different physiological responses, their breathing protocols, and what's the difference between a three-second breath hold and a four-second?

I think the reality is that a lot of the different mechanisms that people talk about are things that they don't really have a good way of measuring.

So all that I've been trying to do recently is try out these different breathing protocols and see how does a nitric oxide level measured in the tissue differ between these different protocols. We're already seeing some pretty consistent patterns across people. If someone does like a Wim Hof-style breathing protocol, very sharp and rapid increase in nitric oxide levels sustained through the duration, and then they just plummet hard after a few minutes. Someone does box breathing, it's more of like a progressive zigzag trend upwards and they stay elevated for longer.

This is just descriptive. I can't really tell you what those mean, what the differences are, which is better or worse and in what context. So this is still something that's really infant in our understanding, I think.

James de Lacey58:19

So the goal would be to do these different breathing patterns and then maybe exercise afterwards and see how that affects various tasks?

Evan Peikon58:19

Yeah, or what we're trying to look at right now is seeing one, how repeatable are these things. So I think there's also some combination of like what is someone's physiology before the protocol and how does that protocol impact it. And then also see if we could correlate these to different measurements. So are one of these protocols better for lowering blood pressure, changing HRV than the other?

And I think if we could start to quantify those things over time, we could better understand one, what are the real effects of these protocols—protocols have become really popular in the past few years—and two, if you have an X goal versus Y goal, is there one that's better or worse for you based on that, instead of just everyone kind of says that their favorite breathing protocol is the best and they just talk about these benefits broadly without really having any real data to support, in my opinion.

James de Lacey59:12

We have to bring you back on there once you've done a little more testing around these different breathing protocols. It'd be interesting, I think, for the listeners as well. But thanks for coming on, Evan, and sharing everything on here. There'll be links in the description if you want to go check Evan's work out. But appreciate it, and we'll see you again.

Evan Peikon59:12

Yeah, thank you for having me on. Appreciate it.