Do You Really Need Zone 2? HIIT, Heat & Smarter Endurance — Jonah Rosner — #411

Interview transcript — Timeline B (final MP3), approved 05:03 raw Zoom cut. Intro, outro, and disclaimer audio are separate recordings and are not transcribed here. Transcript is machine-generated and needs proofreading.

[00:03:01] Dr. Mike T Nelson: Yeah. Thank you so much. Uh, it’s, uh, we’ve both been reading each other’s work, and now we get to chat, which is pretty cool.

[00:03:08] Jonah Rosner: Yeah. It’s always awesome where you, uh, today’s day and age, you meet someone online or you read all their stuff online, you feel like you know them, and then you finally get to connect.

[00:03:15] Dr. Mike T Nelson: Yeah. My first question is, tell me what you think about this statement that everyone for longevity and health purposes should do two to three hours a week of Zone 2 cardio training.

[00:03:31] Jonah Rosner: Yeah. I think if we’re talking about, uh, overall health and longevity, I’d probably say for that absolute statement, I disagree with.

[00:03:38] Jonah Rosner: I think it’s probably a little bit more complex and context-dependent, um, than that. I think the way I like to look at, like Zone 2 versus high-intensity training, and I know a lot of people push back to say that when someone first starts training, they need to do the lower intensity stuff so they can build a base.

[00:03:54] Jonah Rosner: What I will say is that similar to how I think about lifting, that if we give someone a higher intensity stimulus, and that is true for cardiovascular system as well, you’re gonna have a bigger stress on the body or the bigger stress on the system in a smaller amount of time. Because anyone who does ten minutes of HIIT versus ten minutes of easy Zone 2 will tell you ten minutes of HIIT is definitely harder.

[00:04:15] Jonah Rosner: Oof, yeah. So it’s a bigger stress, and a bigger stress typically leads to more adaptation. So when I’m working with an individual whose goal is health and longevity, and a lot of these individuals don’t have a ton of time to train in a week like a professional endurance athlete, we wanna essentially get the most bang for their buck in the amount of time.

[00:04:32] Jonah Rosner: And so if it’s safe to do so for these athletes, I would probably recommend if they can prioritize higher intensity training in a safe way where they’re not gonna mechanically overload their lower body or specific tissues in an unsafe manner, I would imagine that’s gonna lead to better changes in the cardiovascular system, the peripheral muscular system related to metabolism, that will lead to overall better health and longevity gains.

[00:04:55] Jonah Rosner: Because higher intensity, more adaptations over time, which theoretically would lead to better health and longevity.

[00:05:01] Dr. Mike T Nelson: Awesome. And if someone’s just the, the average meathead, you mentioned about not making sure they don’t overdo it, what would be kind of your favorite modes of that? Yeah.

[00:05:11] Jonah Rosner: I think if someone is going to high-intensity interval training early on first before they’ve established a large training load, we probably are gonna stay away from things that come with a lot of mechanical loading or put a lot of stress on the lower body tissues, like the muscles, the tendons, the joints.

[00:05:27] Jonah Rosner: And so that’s mostly running. So anything with those high amounts of ground reaction forces and tissue damage with eccentric loads, and most of that’s gonna be very high-speed running. And we know running has this exponential relationship where the faster you go, it’s not a linear, I go one mile per hour faster, it’s whatever, one times the amount of tissue stress.

[00:05:45] Jonah Rosner: It’s exponential. So for every speed increase, you’re gonna get more and more tissue stress. And so I typically like modes that come with very low mechanical loading. So that’s any typical type of cross-training where people think about cycling, where there’s very not a lot of eccentric contractions.

[00:05:59] Jonah Rosner: People are now doing things, um, whether it’s swimming as well Rowers are the erg machines, but cycling is probably the most common, or even an elliptical I love, or some of those machines. So anything where we’re not dealing with a ton of gravity and eccentric contractions, I think are a great way to do some of these higher intensity intervals with what I would argue, based on my experience and the athletes I’ve worked with and the literature, I would say come with pretty low mechanical risk for injury in my experience.

[00:06:26] Dr. Mike T Nelson: Yeah. I would agree with that because it’s… One of the issues I had years ago was, okay, so I probably need to do more higher intensity stuff, but then I would see my average client, especially when I did a lot more in-person stuff, run, and I’m like, oh- Yeah … dear God. Like- Yes. … I don’t even know if I want you to run a mile at, like, a low pace.

[00:06:44] Jonah Rosner: Exactly. Yeah, if you haven’t- Like, I think this

[00:06:45] Dr. Mike T Nelson: is gonna be a disaster.

[00:06:47] Jonah Rosner: If you haven’t gone for a run in 10 years and then going out and trying to do sprints, that’s probably a recipe for a good old hamstring pull disaster. So I think slowly, the way I like to frame it, people think they misinterpret what I say, and they’ll say, “Oh, he’s telling me to go do four minute all-outs around a track.”

[00:07:01] Jonah Rosner: I’m definitely not. What I would say is I would slowly introduce cross-training, high intensity interval training, and maybe the lower intensity stuff could be running. And then as you build the tissue sh- uh, tolerance with running, then you slowly dose in a progressive manner the running stress.

[00:07:15] Dr. Mike T Nelson: Yeah. I feel like that’s what’s hard, even I’ve gotten a bunch of pushback on this, and I’m sure you have, too, of when you’re putting stuff out on social media, like, it’s…

[00:07:24] Dr. Mike T Nelson: If you’re doing a reel, you’ve got three minutes, or if you’re doing a post, like, there’s some limit to how much characters you can put in. And it’s frustrating because I want people to respect context, but at the same point, you just don’t have enough time or space for people to have enough bandwidth to go through every single exception about everything you’re, you’re talking about.

[00:07:45] Dr. Mike T Nelson: And I think that running seems like it’s, it’s kind of its own… I don’t wanna say it’s its own thing, but it has so many different things that if you’re doing rowing or an assault bike, you don’t have to worry about. You know, like, if you’re on a rower, yes, there’s better form, but you can do a good enough form where you’re not gonna injure yourself and get an effect.

[00:08:05] Dr. Mike T Nelson: Same thing with an assault bike. Where running, you could spend years upon years working on, you know, technique, and then like you said, you’ve got the eccentric overload, you’ve got how people are responding to it, and everything down to what shoes they’re wearing and everything else. Where it just seems like if you put running aside, it, it’s kind of its, its own thing.

[00:08:26] Dr. Mike T Nelson: And unfortunately, a lot of the literature is derived from running when you look at aerobic stuff then, too.

[00:08:32] Jonah Rosner: Yeah. I couldn’t agree more. I think exactly as you alluded to, for a lot of these, like, cross-training devices, you’re probably just gonna naturally optimize your form over time as you learn to do it.

[00:08:42] Jonah Rosner: Mm-hmm. And even if your form’s not great, if you work hard, you’re gonna get a good stimulus. Um- Yeah, you still get a training

[00:08:46] Dr. Mike T Nelson: effect.

[00:08:47] Jonah Rosner: Yeah, you’re still gonna get a training effect. Same thing with running, too, but obviously, as you alluded to, running’s probably a little riskier and just a lot… a little more complex with all the different variables.

[00:08:57] Dr. Mike T Nelson: Does it seem like there’s a resurgence in sprinting, as in running now? I’ve had, like, a couple people hit me up and are like, “Yeah, I wanna get into sprinting.” And these are people who are, you know, 45 to mid-50s. Yeah. My first response is, “That’s amazing.” And then it’s like, “Okay, for God sakes, please don’t go out and run at 90, 95%.”

[00:09:20] Dr. Mike T Nelson: Like, just… And the handful of people I’ve taken through the process, it’s, I don’t know, maybe I’m just hyper-conservative ’cause I don’t want them to get injured. They’re not, usually at that point, they’re not highly competitive athletes. It’s like this isn’t their profession per se. So to me, like, having an injury is kind of on the low acceptability risk.

[00:09:38] Dr. Mike T Nelson: Um, but it- the big thing I just wanna get across to them is that it just, it’s gonna take much longer to get proficient, to push intensity, even if you were younger. And it just seems like everyone’s in a hurry to do the super fast cool sprints or 100-meter repeats or whatever is cool now, I guess.

[00:09:57] Jonah Rosner: Yeah, I definitely have seen a resurgence in sprinting.

[00:10:00] Jonah Rosner: And I think first, I think it is important, exactly like you said, that- Before we increase– A lot of these injury studies where we see are in running-based sports- Mm-hmm … which are exactly cross-training sports, where there is a huge mechanical load every time your foot hits the ground. Even if you’re running slow, an easy zone two run still causes some muscle and tissue damage, which I think a lot of people forget about, even when they say zone two.

[00:10:24] Jonah Rosner: So I think, as you said, it’s important that we know from a lot of this literature when we’re going to running, if we see huge increases in training loads. For example, I’m used to doing a five-mile run, and then that week I go out and do a fifteen-mile run, and I run every day, that’s a huge piece of training load, and your injury risk probably is higher.

[00:10:39] Jonah Rosner: So we just need to slowly progress you because as you slowly progress week by week, your tissues, your muscles, your tendons, your ligaments get used to that stress. They recover from that stress. And so the next time you go out and do it, like any adaptation, they’re more prepared for it. But you just need to slowly progress yourself there.

[00:10:56] Jonah Rosner: And, um, from the standpoint of sprinting, it does seem like sprinting is becoming more and more common. And I think we have some literature. In the literature they call it sprint interval training, where essentially you do, like, an all-out sprint for whatever, ten to thirty seconds. You rest, you recover.

[00:11:11] Jonah Rosner: And we have some really good literature now that that itself leads to a lot of beneficial adaptations from a metabolic cardiovascular standpoint. You could still get some really great metabolic adaptations in the muscle itself, but also from a cardiovascular central standpoint in the heart area. But then also it does lead to some, like, neuromuscular benefits as well.

[00:11:30] Jonah Rosner: Like, you’re gonna activate a ton of muscle because you’re producing a lot of force to sprint, and that can lead to s- maybe not exactly the same adaptations of heavy strength training, but similar adaptations where you recruit a lot of this fast-twitch muscle fiber. Those get stronger. You be– get better at recruiting them.

[00:11:44] Jonah Rosner: And I also think for individuals who have running, endurance running goals, whether it’s five K, half marathon, full marathon, we do see some literature now that including sprint training can improve your running economy, which is how efficient you are, similar to how strength training does, where you kind of raise the individual’s maximum speed capability.

[00:12:02] Jonah Rosner: Then every endurance run is a s- submaximal or more submaximal of your maximum pace. So if it’s essentially a smaller percentage of your maximum pace, that running becomes more easier or it’s more efficient for you.

[00:12:13] Dr. Mike T Nelson: Yeah, I always equate that to in lifting, it’s the, the 1RM- Exactly … is kinda like the big size of your engine, right?

[00:12:20] Dr. Mike T Nelson: I know you’ve worked in the NFL, but, like, if you’re gonna do the NFL Combine, I’ve got two athletes. Like, one athlete, their 1RM bench press is 340. The other one is, like, 235. It’s like, who would I wanna train to do reps with 225? It’s like- Exactly … of course I wanna train the guy who’s got the bigger 1RM.

[00:12:37] Dr. Mike T Nelson: Even if right now he may not perform as well on that test if he’s never done it or anything like that, I guarantee he will absolutely blow the doors off the other person within a few weeks probably, or even just a few practice runs. Just like you said, because everything is so sub

[00:12:53] Jonah Rosner: max. I couldn’t agree more.

[00:12:54] Jonah Rosner: Especially when I work with, um, some of the older athletes now who get into half marathons. A lot of them come to me and say, “Hey, I wonder about a half marathon or qualify for a Boston Marathon at this pace.” And let’s say the pace is a seven-minute per mile pace. But if their maximum sprinting ca- capability is at a 6:30 minute per mile pace, then that ceiling is gonna be what caps them.

[00:13:13] Jonah Rosner: They’re just running way too close to the ceiling for, so for a lot of them, ’cause we know maximum speed, maximum power is something we lose first as we age. We first have to raise the ceiling by exposing them to that sprint stimulus, so then they have room to move that half marathon pace up. If not, they’re kinda crammed by the ceiling

[00:13:30] Dr. Mike T Nelson: Yeah.

[00:13:31] Dr. Mike T Nelson: Do you have any way of doing that? Like, one of the things I’ve done, which I got from, like, what Roger Bannister kinda did, I, I just coined it, I called it, you know, QDR, like quality density repeats. So I’ll take, like, their ideal time or even, like, faster than their ideal time, depending upon the race length, and it’s like, okay, let’s see.

[00:13:50] Dr. Mike T Nelson: You know, assuming your form is good, everything else is good, I’m not worried about your running mechanics, like, can you hit that pace, but what is the distance? Is that a mile, three-quarters of a mile, half a mile, quarter mile? And then I’ll just do repeats. Let’s say you can hit that fast pace at a quarter mile.

[00:14:07] Dr. Mike T Nelson: So great, go run a quarter mile, rest completely, see if you can do it again at that pace, and then we’ll just build up volume there. It’s- And then all of a sudden- Yeah … hey, like, you could… Oh, cool, now you can do a half mile at that pace. Great. And just keep scaling them up over time.

[00:14:21] Jonah Rosner: It’s just… Yeah. It’s progressive overload 101, is what I would say.

[00:14:25] Jonah Rosner: Right. And it’s, a lot of the framework applies. What I like to do when I’m working with an older athlete is, if we do wanna work on maximal sprinting but they’re newer to running, I think a lot of it, actually where I start is, I start at the gym with, like, plyometrics-

[00:14:38] Dr. Mike T Nelson: Oh, yeah …

[00:14:38] Jonah Rosner: um, heavier strength work, maybe things that are a slightly safer environment than them sprinting- For sure

[00:14:43] Jonah Rosner: just to increase the tissue tolerance to stress, get the tendons, everything ready. And then once that’s at a good spot, then maybe we’ll go to, like, accelerations or strides out on a field where it’s, we’ll, again, accelerate up to 80% of max. So we’re not sprinting yet. So there’s a little bit of a progression where we start in a more controlled environment, we still keep it controlled, we get to 80% of max, and then eventually build up to 100% of max.

[00:15:06] Jonah Rosner: And then I take what we call, and I know you’re familiar with, like, a short to long approach.

[00:15:09] Dr. Mike T Nelson: Mm-hmm.

[00:15:10] Jonah Rosner: And Dan Pfaff talks a lot about this, but actually one of my biggest influences for marathon coaching is Renato Canova, and what he does is he does, he’s an Italian marathon coach, a short to long approach where he first gets them sprinting a very high intensity at whatever the desired pace is, or probably typically faster than their race pace, and then he extends it.

[00:15:29] Jonah Rosner: So he essentially just says exactly two or two each week, okay, running at this pace, faster than your marathon pace. Then instead of it being for two minutes, it’s gonna be three minutes at this pace. And just over time, as the tissues have now gotten used to the higher mechanical stimulus, we just extend the amount of time you can maintain that pace, which is probably a metabolic side.

[00:15:49] Dr. Mike T Nelson: Yeah, that’s pretty similar to what I do, depending on the person is I call like the, the barbell or the literature would say it’s like a polarized approach. You know, like on the right end, I’ve got like your high-speed stuff, your mechanics, your, you know, trying to run short distances, but high-quality output.

[00:16:04] Dr. Mike T Nelson: And then on the other end, I might do some zone two, just some basic stuff like just get used to running longer distances, more tissue tolerance. Exactly. I don’t want a high load, you know, per, you know, limb strike or ground reaction forces or all that stuff. And then over time, these will kind of merge a little bit more in the, in the middle as we go.

[00:16:27] Jonah Rosner: Exactly. And I think as we work with older athletes, understanding how this all fits into the week and the time course of recovery of certain tissues becomes very relevant. So if we do like one of those big workouts with a lot of high-speed work and mechanical stress, then maybe we’ll take a day off, and then actually I use a lot of cross-training with these athletes to get the metabolic load.

[00:16:44] Jonah Rosner: So essentially, let’s say Tuesday we did a big track workout to prepare you for your marathon. That’s important, so your tissues get used to that high stress, and metabolically you get used to it. But then those tissues, the tendons, the bones, ligaments, the mu- they just need time to recover from that damage.

[00:16:58] Jonah Rosner: And so we’ll give them a day or two, and in those days, we can do easy running, which still loads it, or do cross-training, which probably doesn’t load it really at all. And that cross-training can still give you a very important metabolic stimulus, cardiovascular adaptations over time if we’re consistent with it.

[00:17:12] Jonah Rosner: But then you still allow the tissues in the lower limbs to recover, so they’re ready to go again for another high important quality session.

[00:17:18] Dr. Mike T Nelson: Yeah. Yeah, I love that because you can… Some people, when they look at the program, they’re like, “You’re an idiot. Like, I’m doing the rower, and I’m doing an assault bike.”

[00:17:27] Dr. Mike T Nelson: And I’m like, “But y- you’re, you don’t have the capacity to only be-” Exactly … running without me just blowing you up in, like, three weeks. So we’re costing time because we can’t load your structure to- Exactly … quote, quote, “the perfect.” But I could put you on a rower and have you do 30-second repeats. Hell, sometimes just even do two of those.

[00:17:48] Dr. Mike T Nelson: Not gonna beat you up. It’s concentric only. It’s full body.

[00:17:52] Jonah Rosner: Exactly.

[00:17:52] Dr. Mike T Nelson: And I can get a lot of metabolic demand from that without risking your tissues and everything else.

[00:17:58] Jonah Rosner: It’s one of the biggest things I’ve thought about over these past years as I’ve worked with team sports, and I’ve moved more into running, and definitely older athletes.

[00:18:05] Jonah Rosner: A lot of the younger high-volume athletes who I work with, they can run twice a day every day, and most of them seem to be okay. Oh, yeah, they’re fine. Who cares? Yeah, but some of them, they’ll come back from injury, and they need some of this, um, probably just more thought in how we progress the mechanical load.

[00:18:17] Jonah Rosner: Yeah. But something that’s really I’ve thought about is how do we separate mechanical and metabolic load? Mm-hmm. They’re both really hard to quantify- Yeah … so a lot of it’s probably just subjective and anecdotal in nature. But with a lot of the modern technology, we can essentially say, okay, think about typically, like, why does a runner, a, a lead endurance runner maybe runs 10 to 15 hour a week.

[00:18:35] Jonah Rosner: An elite cyclist cycles 30 hours a week, 25 to 30. Yeah. So why is that? It’s because the runner mechanically is limited. Yep. You can only handle so much mechanical tissue stress, where a cyclist doesn’t deal with that. So that essentially tells you what the limiting system is for these elite runners. And so if we apply that idea to some of these other runners we work with as well, it’s like, okay, we know you can’t handle any more mechanical loading, but you probably have room to spare on this metabolic side of it, where we can add more metabolic and cardiovascular stress, um, to potentially improve your running performance.

[00:19:08] Jonah Rosner: And so that’s where we could separate the mechanical and the metabolic and say, okay, how do we accrue a high metabolic load with a low meta- with a low mechanical load? And that’s where the cross-training comes in. But then also we could do things like heat training, when people go to altitude, blood flow restriction training.

[00:19:23] Jonah Rosner: These are all things where if I run with… in heat, metabolically, that’s much harder, but I’m still running at a slower speed, but getting a bigger metabolic stimulus. And when I run at a slower speed, it’s a less mechanical load, for example.

[00:19:37] Dr. Mike T Nelson: Talk to me about heat. That’s one thing I’ve been fascinated with, and obviously, you know, I’m biased ’cause I do the physiologic flexibility cert, and one of the pillars is, you know, cold and, and heat in terms of temperature.

[00:19:47] Dr. Mike T Nelson: But especially on the heat side, if you have access to it or people live in a warm environment, I, I just… I don’t know if you would agree on the literature on this, but I do think there is something to being heat acclimated that goes beyond- Oh, 100% … just being used to that environment. There just seems like if you’re heat acclimated, and you’re doing well, and it’s past, you know, the two weeks with the classic, you know, increase in, you know, plasma volume and stuff like that, I just see if the temperature drops, the athlete who is heat acclimated, even though they’re not running in the heat, does better than the athlete who was not heat acclimated.

[00:20:26] Dr. Mike T Nelson: I don’t know if you’ve seen such a thing.

[00:20:28] Jonah Rosner: I’ve seen the literature for sure, and there’s definitely some literature about heat training transferring over to temperate conditions.

[00:20:33] Dr. Mike T Nelson: Yes.

[00:20:34] Jonah Rosner: And we could talk about that a little bit right now. I think number one- Yeah, that’d be great … if you’re, if you’re racing in heat, you have to do heat acclimatization.

[00:20:40] Jonah Rosner: Yeah, no question. You have to get ready for the heat or you’re not gonna, you’re not gonna survive. You’ll get destroyed. Yeah. We know that the typical protocols are within 14 da- two weeks, you typically get a lot of those initial heat, um- Mm-hmm … adaptations, which essentially like if you… We typically recommend 10 out of 14 days, so 5 days a week you’re doing heat training.

[00:20:58] Jonah Rosner: And the typical sessions are like easier zone two, zone three, heart rate, whatever zone two heart rate is, um, for 60 minutes or longer, 45 to 60 minutes, and you can have a combination of active and passive, where essentially you do things like exercise in the heat and then I go in the hot tub or the sauna after.

[00:21:14] Jonah Rosner: And it’s just about keeping your core temperature as high as you can or past a certain point for probably that 60 minutes plus with a combination of active, um, and passive. Since when I’m working out actively, I produce metabolic heat and that heats my body up. But essentially what happens within those two weeks, if you do it daily, you increase your sweat rate.

[00:21:32] Jonah Rosner: Obviously, sweating is how your body dissipates heat or dumps heat as one of the main ways. You get better at holding onto electrolytes in the system. Um, you… One of the early adaptations is you actually increase your plasma volume, or just the overall volume of the blood. So obviously, if you have more blood, that helps with heat dissipation.

[00:21:49] Jonah Rosner: But also one of the big things that happens in heat, why it makes it so hard, is your body sends blood and oxygen to the muscles to work because oxygen is an important- Um, to create that energy and ATP. But then when you’re in heat, as we talked about, the way your body gets rid of heat or dumps heat is it has to send blood to the skin, and that essentially dumps heat.

[00:22:10] Jonah Rosner: So if I’m sending blood to the skin, that’s less blood typically that’s gonna go to the muscles. So there’s almost this competition. So less blood to the muscles makes it a little harder for those muscles to work. That’s why the heartbeat goes up. It’s trying to get more blood flow. So by increasing that plasma volume, you have more blood to distribute, so more blood for the skin for cooling and then more blood to the working muscles to actually produce the energy to move you forward.

[00:22:32] Jonah Rosner: And so we get– And you just get better at tolerating the cr- increases in heat as well. So there’s all these adaptations that happen within those two weeks to potentially make you better at exercising in the heat. But now there is other research coming out that essentially says we know that when we’re exercising in heat, we get all these things like heat shock proteins, all these other things that potentially could benefit.

[00:22:53] Jonah Rosner: But there are some papers now that when people extend the heat stimulus for maybe four or five weeks, um, daily or five out of seven days a week, we can say, and a combination of that active… Actually, the, the study that’s been really interesting was a passive one where they actually did all hot tubs after they did a session.

[00:23:11] Jonah Rosner: So they would do the typical forty-five to sixty-minute run, and then they would go sit in a very hot hot tub, and they progressively made the hot tub hotter over time for progressive overload.

[00:23:19] Dr. Mike T Nelson: Oh, nice.

[00:23:19] Jonah Rosner: Nice. So essentially what happened is, um, they got a very similar response to altitude, probably slightly different mechanisms- Hmm

[00:23:25] Jonah Rosner: where you got that initial increase in plasma volume But over time, the body sensed that increase in plasma volume, and we don’t have to get into all of the nerdy details, but something that your kidneys do potentially or what happens to the body, you have a ratio of plasma volume to the actual red blood cells or hematocrit and all that stuff, and your body wants to maintain homeostasis.

[00:23:47] Jonah Rosner: So if your body says, “Oh, right now I have a lot more blood volume relative to actual red blood cells,” the kidneys say, “Okay, we need to fix that, and so we’re gonna make more red blood cells. We’re gonna increase hemoglobin, which carries the oxygen.” So what happens when we go to altitude, when there’s lower partial pressure of oxygen or, or all that stuff that happens at altitude, your body responds by making more hemoglobin so you have more oxygen to carry around.

[00:24:09] Jonah Rosner: And so we see a similar response where prolonged heat training for four to five s- weeks is, is… The body wants to maintain homeostasis, so when it senses that increase in plasma volume, it says, “Okay, now I have to make more hemoglobin mass, more red blood cells,” you get s- that similar response to altitude.

[00:24:24] Jonah Rosner: And it can potentially raise your VO2 max, and also because we got that increase in plasma volume, every… That tends to actually increase overall stroke volume and VO2 max because we know to increase stroke volume, more blood flow stretches the heart more. Overall blood volume potentially leads to essentially more blood your heart can pump with each beat, which is a positive adaptation for VO2 max.

[00:24:45] Jonah Rosner: And that’s really interesting because if we increase your VO2 max or we increase just your hemoglobin, so circulating in the blood of red blood cells, that’s gonna transfer over to non-heat environments, right? Because if I have more blood to send, more oxygen to send, and higher VO2 max, then even if I’m not in heat, those are adaptations that all make you potentially a better endurance athlete.

[00:25:02] Jonah Rosner: I know that was a lot. Hopefully, hopefully that makes sense. No, it’s perfect. I love it. I can clarify any of it. But that’s what my thoughts about potentially how it would help in temperate conditions, but also just all the adaptations, better sweater, holding on to more electrolytes, I think could help as well.

[00:25:16] Dr. Mike T Nelson: Yeah, and if you can just cram more blood flow into the heart via the Frank-Starling mechanism- Exactly … you get that kind of stretch response, which is- Exactly … almost like free output, so to speak. Right? Exactly. You, you get a lot more… You’re not putting a lot more energy into the system to get it out.

[00:25:33] Dr. Mike T Nelson: It’s almost like a, a- It’s just a stretch response … uptick in efficiency. Yeah.

[00:25:36] Jonah Rosner: Yeah. Yeah, exactly. The Frank-Starling method. I didn’t know how deep you wanted to go, but that’s exactly what happens. No, yeah. Right? Because you have more plasma volume from the heat adaptations, so the heart stretches more with each beat.

[00:25:46] Jonah Rosner: It uses the heart’s natural elasticity. It’s essentially f- free extra blood volume, as you alluded to, which I think it helps. It’s… You’re essentially able to maintain the same exercise for a lower heart rate, since each beat delivers more blood.

[00:25:58] Dr. Mike T Nelson: Yeah. No, that, that’s super cool. I didn’t know the part about that the red blood cell mass goes up to match it, which, which makes sense because that’s the part I…

[00:26:07] Dr. Mike T Nelson: In my head, I was trying to figure out. I’m like, I keep seeing this trend happen over and over again. I’m like, “Well, what’s the mechanism?” Because plasma volume is usually maxed out, so that, that makes perfect sense. That’s awesome.

[00:26:18] Jonah Rosner: Yeah, and I think it’s this new theory as we’re seeing these adaptations happen.

[00:26:22] Dr. Mike T Nelson: Mm-hmm. Like,

[00:26:22] Jonah Rosner: this hematocrit or crit meter theory where it’s like, okay, the body probably wants to maintain this ratio of hematocrit and all, so it’s naturally gonna upregulate the red blood cell production.

[00:26:34] Dr. Mike T Nelson: Yeah, that’s cool. Do you, do you think there’s something related to I know kind of an acute effect.

[00:26:41] Dr. Mike T Nelson: So the first time I saw this was years ago. I, I saw, I think it was Laird Hamilton stuck an assault bike in a sauna, and I had talked to people who had trained with him, and he’s like, “Yeah, he first put– burned his hands on it, so he had to use, uh, oven mitts on the, on the handles because it was- That’s so funny

[00:27:02] Dr. Mike T Nelson: it was so hot in the sauna that he’s in there exercising in the heat doing this,” which again, I, I would not recommend this to people. You can way overextend yourself pretty fast. But I do think there is something to moving heated blood around the body because it’s a different adaptation- Yeah … than sitting passively because you have now thrown in the component of muscular work at the same time, especially for these short bursts of high output that is probably harder to do otherwise.

[00:27:39] Dr. Mike T Nelson: I just think there, there is probably some adaptation there as long as you don’t completely nuke your system doing it with stress.

[00:27:47] Jonah Rosner: Yeah, I agree. Because we know, like, why when we exercise do we get so overheated. I think people don’t realize, like a car, we’re very inefficient. Mm-hmm. So the amount of energy you produce, only about 20%, and it depends on the individual-

[00:28:00] Dr. Mike T Nelson: Yeah

[00:28:00] Jonah Rosner: is actually gonna move you forward, um, in regards to locomotion, and 80% is heat dissipation. So out of all that 80% of it is heat created from the creation of ATP and energy. Um, and so essentially, that heats us up, um, moving us forward, creating energy, and as we move up to higher intensities, we know that we create more heat as we have to work harder.

[00:28:24] Jonah Rosner: And so the body has to get good at dissipating that heat from metabolic work. So I think it is interesting where there’s been arguments back and forth, is active or passive better for heat adaptation? And I think personally, my biases from literature I’ve seen, I don’t think passive on its own is gonna be ever as effective as active or a combination of active and passive together.

[00:28:50] Jonah Rosner: ’Cause exactly as you alluded to, I think the body does need to get used to dissipating the heat from metabolic work at higher intensities as well. And there’s slightly different adaptations where it’s how do we, um, heat adaptations like humidity versus regular heat, where the skin, um, potentially dealing, dealing with the skin, um, temperature versus core body temperature.

[00:29:12] Jonah Rosner: So there’s all these interesting nuances you could get into.

[00:29:15] Dr. Mike T Nelson: Yeah. And at the end of the day, your brain is still having to manage all this, right? So it’s- Exactly … gonna steal blood flow to make sure you’re upright and don’t friggin’ face dive as you’re on the asphalt.

[00:29:27] Jonah Rosner: Yeah. And there’s the element of perception, right?

[00:29:29] Jonah Rosner: Yeah. Like, we know that one of the adaptations to heat is thermo perception, but your body and your brain just get better at saying, “Okay, I’ve been exposed to this before.” I know it’s uncomfortable, but I’m better at dealing with it and I’m not gonna shut my body down. So you get better at perception of heat.

[00:29:43] Jonah Rosner: That’s why people now try to use a lot of stuff that essentially, um, reduce the thermo perception.

[00:29:49] Dr. Mike T Nelson: Would that be like cooling around the neck to try to tell- Exactly … the brain it’s a little bit cooler? Exactly. Does that make sense? Like, you’re cooling the blood flow as it’s coming into the brain, but I, I don’t know.

[00:30:02] Dr. Mike T Nelson: I’ve seen that backfire a few times. Again, it’s anecdotal because you, in essence, I get what they’re trying to do. You’re trying to, like, overclock your system a little bit, but I’ve seen that backfire where people have actually just passed out and have been, I’d say, less aware of the true environment of what’s going on.

[00:30:24] Dr. Mike T Nelson: So I don’t know. I’m not as big a fan on that, but I don’t know what your thoughts are.

[00:30:28] Jonah Rosner: Yeah. It’s one of those. Again, the literature around them isn’t too conclusive in regards to improving- Mm-hmm … performance, so that’s exactly right. Obviously, like menthol is something people would do to reduce- Yeah … the thermal perception as well, so that’s an example.

[00:30:40] Dr. Mike T Nelson: Very cool. Do you think there’s benefits on the opposite side to, like, cold? Like, cold water immersion? I know that’s a very-

[00:30:47] Jonah Rosner: Yeah. I mean,

[00:30:48] Dr. Mike T Nelson: I think- … polarizing topic now.

[00:30:50] Jonah Rosner: Yeah, it’s definitely polarizing. It’s definitely… I’m not as confident in myself about the literature here. Um, I do think if you’re gonna be exercising in cold, if you’re doing, like, some event in cold, it’s probably good to prepare yourself- Sure

[00:31:01] Jonah Rosner: um, and just get used to those demands because of sensitivity. In regards to cold water immersion, I definitely think from a recovery standpoint, I’ve become less convinced or very skeptical, especially in recent years with some of the evidence that has come out where it not really have any, any potential benefits from my bias or what I’ve seen for improving recovery, and if anything, potentially can harm recovery or make it, um, harder to recover.

[00:31:26] Jonah Rosner: I feel like now it’s pretty conclusive that w- if you consistently use cold water immersion after strength training, it definitely can slightly blunt hypertrophy- Mm … um, related adaptations. And then obviously there’s some interesting stuff. Um, the lab, um, Cas Fieux and Jorn Trommelen have some- Yeah

[00:31:43] Jonah Rosner: interesting papers they did. Dr. Fieux has been on the podcast. Yeah. Yeah. Yeah, he’s great. Um, what they looked- Oh, he’s awesome. Love that dude … they looked at cold water immersion and act- or sorry, immersion in one limb versus another limb- Mm-hmm … and then actually tracked the amino acid pool. And again, they saw that when the leg was emerged in cold water, that it had less amino acid delivery to the muscles, which potentially could harm recovery or adaptation, again, ’cause your body is probably not gonna send blood flow to that, um, limb that’s emerged in cold water.

[00:32:11] Jonah Rosner: But the other limb saw, in regular conditions, just as much blood flow and amino acids as you would normally expect. So if you got amino acids there less, then just level, less overall substrate delivery is delayed, and potentially that could affect adaptation. Because you’re not, you’re not getting blood flow there essentially.

[00:32:28] Dr. Mike T Nelson: Yeah. What are your thoughts on this? I did this for a while, that I would drag the rower out in the, the heat in the summer, and then my goal was to increase the density of… I think I was doing… What was I doing? I think like four to six minute repeats, so like VO2 max like type stuff in the heat. But then in between, I would go back in and do the cold water immersion, and then I would go back and repeat it in the heat.

[00:32:56] Dr. Mike T Nelson: So my thought, what I noticed was, I could pretty dramatically increase the density of, let’s say I’m doing that for three rounds, by basically using the cold water immersion to dump the heat load in between. I don’t think this is best for, uh, heat adaptation, but my thought was, if I could still train in the heat but compress the amount of work that I’m doing by artificially offloading the heat, is there a benefit to it?

[00:33:26] Dr. Mike T Nelson: And- Yes … I did it for a while. Yeah. My density seemed to go up, but I stopped doing it because fucking pain in the ass because I- Dude, yeah. I was gonna say logistically- … I come back out completely wet, put all my clothes on, and all this other shit to do in between.

[00:33:39] Jonah Rosner: L- logistically, that sounds like a nightmare.

[00:33:42] Jonah Rosner: It

[00:33:42] Dr. Mike T Nelson: was. But what

[00:33:42] Jonah Rosner: I was gonna say is, I think it’s just all different ways we can manipulate the workout. As you alluded to, like if you’re going back in and getting cold, that’s probably gonna allow you to produce more output or power- Right … on each interval. That’s what I

[00:33:52] Dr. Mike T Nelson: noticed, yeah.

[00:33:53] Jonah Rosner: So if you produce more power or more output, that’s more work you complete an interval, and you’re getting more load and potentially better adaptation.

[00:34:01] Jonah Rosner: But then you could go on the other side and make the argument that says, well, then the heat stress by not cooling yourself off, you’re gonna have a higher metabolic load even if you don’t produce as much- Correct … power or watts like internally. So it’s all about that differentiation between external and internal load, and asking yourself, what is the goal of the session?

[00:34:17] Jonah Rosner: Do I want to do as much internal work as possible and reduce the mechanical load or the me- the external output? Or vice versa, is my goal here because I’m a sprinter, or the goal of this session is to get as high mechanical and power output stimulus as possible to prepare my tissues and get maybe some fast twitch adaptations.

[00:34:37] Jonah Rosner: Then maybe I’m, want to reduce the internal load so I can produce as much external work as possible. And so I think you get into all this interesting thing where you say, what’s the goal of this session? Do I wanna potentially reduce mechanical loads so I can get a big metabolic stimulus for less cost, the recovery cost, or vice versa?

[00:34:52] Jonah Rosner: And that’s how I started to look at heat as well, where essentially we can manipulate heat, the ambient conditions, where we do it to potentially alter the mechanical versus metabolic load, how we were talking about earlier.

[00:35:05] Dr. Mike T Nelson: Very cool. Uh, you mentioned altitude. What are your thoughts about, let’s say you have…

[00:35:11] Dr. Mike T Nelson: There’s these, I know these places are popping up now, like exercise at low partial pressure of oxygen or even just low oxygen environments to stimulate altitude. And so let’s say you, you have the perfect setup. You can go hypoxic, you can go hyperoxic, you can exercise in it. Yeah. You could do whatever you want.

[00:35:34] Dr. Mike T Nelson: And you said, “Okay, I’m X person, wanna qualify for the Olympics.” Like, w-what would you do with that person if they’re doing, let’s say, running as that? Would you– How would you balance that out? What would you do?

[00:35:46] Jonah Rosner: Yeah. Yeah, it’s really great. I think if someone has the goal of running as fast as a marathon, half marathon, a specific race as possible, we definitely can strategically use altitude.

[00:35:58] Jonah Rosner: Altitude is definitely not my area of expertise, but from my understanding of the literature and talking to others, we definitely seems like we get the best adaptations from altitude from this, um, live high approach, train low approach, you could say. But essentially, the idea is you probably need to be at altitude for a decent amount of time throughout the day, um, to get the most adaptations in the hemoglobin mass as possible.

[00:36:22] Jonah Rosner: So rather than having maybe a chamber where you go, um, for half an hour a day for a workout where you reduce the partial pressure, you would actually live. That’s why all these athletes are living in Boulder or some of these places in the US at altitude, because by being exposed to it for several hours in a day or living there or sleeping there, then that’s where you potentially get the most adaptation.

[00:36:43] Jonah Rosner: So it does seem like you need to be there for a long time. Um, so they’ll be there. And then what they do is they do a lot of their easy running there as well. But then when they have to do a high intensity session or a VO2 max session or a workout, they’ll actually go down to more sea level. And that’s because if you work out at altitude, you’re gonna produce less external work, just as we said, because those essentially, w- um, the way oxygen, um, it works is the s- the parts…

[00:37:09] Jonah Rosner: It’s just harder, um, for your body to set– your, your body essentially has less oxygen available, I think would be an easy way to say it. Um, so because of that, it makes these high intensity workouts harder, since oxygen is obviously a lim- typically a limiting factor there. So then they’ll go to sea level where there’s more oxygen and allows them to complete those sessions at higher intensities and higher speeds, which leads to more mechanical work to prepare those tissues for the specific demands.

[00:37:36] Jonah Rosner: And then typically what they do is they’ll go to a race. So they do an altitude block where they’ll be there maybe for a few months, two or three months, or we typically recommend you stay at least for five weeks, and then they’ll go down a few weeks before to sea level, um, wherever they’re gonna race at, where they do like their final sessions, um, is typically how I recommend it.

[00:37:55] Jonah Rosner: I don’t know what you’ve seen in regards to altitude or have used it historically, but that’s typically what I recommend. But I do think there is a use case for these rooms now where, again, if I wanna– or things like blood flow restriction training where essentially I wanna increase the metabolic load but reduce the mechanical load.

[00:38:12] Jonah Rosner: If someone’s hurt, for example, and can’t run at faster speeds, we could go into one of these altitude rooms where we essentially mimic altitude. It’s slightly different, but it makes the workout harder. So metabolically, it’s gonna be harder internally, but externally, you won’t complete as much work, so maybe the tissues aren’t ready to handle that work

[00:38:29] Dr. Mike T Nelson: Yeah.

[00:38:29] Dr. Mike T Nelson: No, I think that’s cool. I agree with that. Like, I, in my head, and again, I don’t have any data on this, is I would move someone to altitude like, you know, Denver, Boulder, et cetera. And then in a perfect scenario, I would love to test a hyperoxic room, and all of their high-intensity stuff would be done in the hyperoxic room.

[00:38:50] Dr. Mike T Nelson: Yeah. So you would save them the travel to lower sea level, and you could even go beyond sea level. So again, you’re- Yeah … you’re raising that top end ceiling that I, I’ve kept looking at literature on this, and there’s one super old study where they took a, like almost one of those, looks like a diving chamber, but it’s basically a hard shell chamber that they stuck a bike in, and they did it in hyperoxic conditions, and they did see an increase in performance.

[00:39:19] Dr. Mike T Nelson: This is just a one-off session. This wasn’t a chronic study. But what was super cool is they then tested them, I think the next day, in the normal oxic environment, and it didn’t seem to transfer. Again, you could argue maybe it’s not gonna transfer ’cause it’s a chronic adaptation, not an acute change. Um, but I’m curious if you did it with repeated sessions in a hyperoxic condition because you can get that higher output.

[00:39:44] Dr. Mike T Nelson: My guess is it would transfer at some point, and then you would have the background of the hypoxilic environment that’s still keeping the red blood cell mass and all these other adaptations.

[00:39:57] Jonah Rosner: Exactly. Yeah. Altitude research is very hard to do just because- Kind of, yeah … of keeping people at altitude for a long time.

[00:40:02] Jonah Rosner: Can’t go

[00:40:02] Dr. Mike T Nelson: placebo either.

[00:40:03] Jonah Rosner: And there’s all these other variables, exactly, to control for. It’s like, okay, if I have a control group who’s at sea level, but all the workouts that are higher intensities because they’re not dealing with altitude, is it just because they’re working out at higher intensities- Yep

[00:40:14] Jonah Rosner: versus the altitude group? So altitude research is really hard, and for the people who control the training loads, um, it’s very difficult. But I, I definitely agree. I think if you… And that’s what best practice typically is, the live high, train low. If you do those high-intensity sessions consistently at sea level where you’re producing more external output, I would argue that potentially could lead to good adaptations over time that should transfer.

[00:40:36] Dr. Mike T Nelson: Yeah, I would agree with that. Um, related to that, have you looked at any of the research on what’s called, like, EWOT, so exercise with oxygen therapy? So you’re not necessarily changing partial pressure- Yeah … per se, but you’re going hypo and hyperoxic, but you’re not changing pressure on it.

[00:40:55] Jonah Rosner: Yeah. I’ve definitely seen some of that stuff.

[00:40:57] Jonah Rosner: I’m not an expert, so it’d be hard for me to speak upon it. But yeah, from my understanding, exactly as you allude to, it’s just where altitude changes the partial pressure, this doesn’t actually change the partial pressure. But no, I don’t, I don’t know enough about those, honestly. Have you seen anything cool?

[00:41:11] Dr. Mike T Nelson: I can’t point to any research. I had a long discussion with Kyle Dietz about this once, ’cause he’s got a few of the machines, and he was saying in his high-level athletes, he saw a huge difference, and then he sent me, ’cause it’s Cellie or maybe it was somebody related to him, some… There’s some really old Russian research, and their conclusion, as far as I can make heads or tails out of, was that the only time that the hyperoxic works without pressure changes is if you immediately switch from a hypooxic condition.

[00:41:44] Dr. Mike T Nelson: So you would have someone exercise, right? So you’re depleting oxygen out a little bit, and maybe you drop the- Yeah … inhaled pressure of oxygen, and then you have them do, like, a hard sprint, but now you do the sprint immediately after in a hyperoxic condition. And supposedly, it’s this switching, going from hypo to hyper in a very, very short period of time, is where you see more of the beneficial adaptations.

[00:42:08] Dr. Mike T Nelson: But again- Yeah … it’s a lot of- Makes sense

[00:42:10] Jonah Rosner: to me …

[00:42:10] Dr. Mike T Nelson: anecdotal and who knows? Yeah.

[00:42:13] Jonah Rosner: Yeah, exactly. It’s one of those ones where we don’t really know, I would say.

[00:42:17] Dr. Mike T Nelson: Yeah. Very cool. Um, do you use blood flow restriction training as kind of a, a poor man’s- Yeah … way of, of changing a lot of the metabolic environment? I, I don’t-

[00:42:29] Jonah Rosner: Yeah, exactly

[00:42:30] Jonah Rosner: it’s kind of an

[00:42:30] Dr. Mike T Nelson: oversimplification.

[00:42:31] Jonah Rosner: But yeah, exactly. I think sometimes people think it’s very similar to altitude. Well, it’s a little different where it’s more of the peripheral-

[00:42:36] Dr. Mike T Nelson: Mm-hmm …

[00:42:36] Jonah Rosner: um, oxygen environment it actually is itself. But yeah, so I’ve been a big fan of blood flow restriction training for a while.

[00:42:42] Jonah Rosner: So first started using that if I were with those athletes, um, probably a lot in a return to play situation or where we just wanted to offload them and going after some of the hypertrophy and strength adaptations, and I still do that a lot with runners. Runners are definitely not too keen to always lift.

[00:42:56] Jonah Rosner: Yeah. But they’ll be more open to it if we just say, “You don’t have to load heavy. You won’t get as sore, and we could get a lot of the very similar hypertrophy adaptations or potentially a good proportion of the maximal strength adaptations.” But then also, as you alluded to, there’s newer research coming out where there’s probably other use cases because what is blood flow restriction doing?

[00:43:13] Jonah Rosner: It’s creating a high metabolic stress environment in the peripheral, in the limbs, and so that probably is gonna lead to some metabolic adaptations. Um, some of the peripheral ones where it’s increasing the capillaries, mitochondrial density and function, and then also potentially there’s a recovery aspect.

[00:43:28] Jonah Rosner: ’Cause you can make the argument, and we’re seeing some new literature come out, where if you do rounds of occlusion and then you get release, so fusion, reperfusion, where you get old blood flow sending back to the heart, new blood flow being rushed in, potentially that can help clear waste product and send fresh oxygen and nutrients to those tissues and potentially help with the recovery process.

[00:43:49] Dr. Mike T Nelson: Do you think some of that might be, and I did some research on like FMD, so like flow media dilation- Exactly … that in essence when you’re doing BFR, do you think there might be a training of the blood vessels locally to be better adapted to controlling blood flow? Because now you have this- I 100% … massive-

[00:44:08] Jonah Rosner: Yeah

[00:44:08] Dr. Mike T Nelson: influx which causes the sheer stress, which causes the dilation and-

[00:44:12] Jonah Rosner: Exactly. There’s a great paper I have to send you where they essentially did this study. Oh, cool. One leg BFR, one leg not. And one of the main adaptations they argued, exactly as you alluded to, because when you do that fusion reperfusion with blood flow restriction training, you’re getting this huge influx of blood- Mm

[00:44:27] Jonah Rosner: which creates all this sheer stress at the local capillaries, the, um, and all the local, um, sorry, the local capillaries to the muscle and all, all the blood vessels. And that sheer stress is quite a strong signal for VGF or adaptation to more capillaries, et cetera. Yeah. But also probably the flow media dilation to improve blood flow control.

[00:44:47] Jonah Rosner: So one of the main theories and what they saw, they did some stuff with like, uh, NIRS or near-infrared spectrometry- Yep … and also measured blood flow. They actually saw the tissues, their theory was, got better at that flow media dilation. So it was better at sending blood flow to the tissues where they needed it and not when they didn’t need it, and dealing with kind of that on off of blood flow.

[00:45:05] Jonah Rosner: And they argued that that was one of the potential adaptations that improved the metabolic efficiency of the musculature.

[00:45:11] Dr. Mike T Nelson: That’s cool. I mean, that’s one thing I’ve done, but I don’t have enough, I’d say, data to say yay or nay is if I have someone who’s more of an endurance athlete and we stick a, a moxie like so, right?

[00:45:22] Dr. Mike T Nelson: So a NIRS device on the muscle, say the quad, and I just for the life of me, can’t get them to desaturate, right? So I can’t get them to drop, uh, oxygen out of the muscle to a low level. I’ll do some blood flow restriction training on that limb as a theory of, again, giving it this massive stimulus of, okay, we’re gonna restrict, you know, venous, basically we’re gonna allow blood more to not exchange out as much, and you’re forcing almost like depletion of oxygen from it, and then go back to their normal training at some point.

[00:45:59] Dr. Mike T Nelson: I don’t have enough data to say that it changes the SMO too, but it, it seems to let them deplete oxygen a little bit better over time than anecdotally.

[00:46:09] Jonah Rosner: E- exactly. And anecdotally, and from my understanding of the literature, I would, uh, make that argument as well

[00:46:16] Dr. Mike T Nelson: Yeah. So for people who are listening, it’s kind of a cool way you can then…

[00:46:20] Dr. Mike T Nelson: You know, that’s one of the reasons I bought a metabolic cart that has, uh, nears that you can put on at the same time, ’cause I’m like, “Oh, so now I can look at these full body changes and, you know, RER and, and flow rates and all this stuff, but I can also look at, okay, what’s going on at, like, the local muscular level- Exactly

[00:46:38] Dr. Mike T Nelson: as best we can tell, and see is it just, hey, maybe your respiratory rate’s too low, or maybe you’re just burning carbohydrates too soon, or maybe it’s none of that is… Maybe all that’s great, but you can’t… Your SMO2 never goes below, like, frigging 55. Like, you just can’t run the muscle hard enough to get down to deplete oxygen out of it.

[00:47:00] Dr. Mike T Nelson: So it kinda gives you an idea of where their limiter might actually stay.

[00:47:04] Jonah Rosner: Yeah. Some of that stuff is really interesting, where we see if someone’s limited potentially centrally versus periphery-

[00:47:10] Dr. Mike T Nelson: Yeah …

[00:47:11] Jonah Rosner: and how we would potentially train that. It’s hard to know. But for me, some of these stuff like blood flow restriction training, a lot of this as well, typically the cost is pretty low.

[00:47:20] Jonah Rosner: Yeah. It doesn’t add a ton of extra mechanical stress, and it often is a novel stimulus. Even if they’re super well-trained- Oh, yeah … it’s really hard to mimic some of the sheer stress you’ll get metabolically, or just, like, the metabolic occlusion you would get, which leads to a different type of stress, and I think that novelty can lead to potential adaptations as well.

[00:47:38] Dr. Mike T Nelson: Do you

[00:47:39] Dr. Mike T Nelson: think

[00:47:39] Jonah Rosner: there’s some- Especially peripherally, you can overload.

[00:47:41] Dr. Mike T Nelson: Yeah. Do you think there’s something interesting hemodynamically going on? Because I’ve noticed this on myself and even on clients, even just doing BFR arm training, which I don’t do much of, whenever I do any type of BFR, my heart rate goes up substantially higher than it would otherwise.

[00:48:03] Dr. Mike T Nelson: I don’t know if you’ve noticed-

[00:48:04] Jonah Rosner: Yeah … that

[00:48:04] Dr. Mike T Nelson: also.

[00:48:06] Jonah Rosner: I agree. It definitely has happened to me as well, and I have thought about that hemodynamic standpoint and if that would potentially lead to adaptations. But again, it’s one of those ones where I just don’t… Like, is that potentially gonna create a big adaptation than just doing a high intensity interval training session hemodynamically?

[00:48:20] Jonah Rosner: Probably not. I don’t know. Exactly. Yeah. That’s my thought. It’s just, like, if I do four by four minutes intervals, I feel like that’s gonna be a bigger hemodynamic stress.

[00:48:27] Dr. Mike T Nelson: Oh, for sure.

[00:48:29] Jonah Rosner: Yeah. But again, my overall load might be less, so it is interesting too. I’m very, finding it very interesting all these ways we could potentially increase metabolic load with very little recovery cost.

[00:48:39] Dr. Mike T Nelson: Yeah. I’ve noticed that with flywheel training too. Like, it just seems like just doing multiple higher reps with the flywheel just jacks up my heart rate, and most people higher than not using a flywheel to do it. And I, I don’t know if it’s just- Exactly … more muscle contraction, so you’re pushing blood flow somewhere else or what, I don’t know, but it’s interesting.

[00:49:01] Dr. Mike T Nelson: Again, does it probably make a big difference in the grand scheme of things? Eh, probably not, but it’s, it’s just a interesting, uh, effect I’ve noticed.

[00:49:09] Jonah Rosner: Yeah. It’s the same thing. Exactly.

[00:49:13] Dr. Mike T Nelson: Have you looked at, uh, the, there’s a company called AIR, A-E-I-R, and I’ve talked to them a fair amount. They’re in Minnesota here.

[00:49:20] Dr. Mike T Nelson: They do full body CO2. Have you looked at that at all?

[00:49:24] Jonah Rosner: Yeah. I’m just curious on your thoughts. So that, again, so it’s actually funny. People are doing, uh, CO2 rebreathing. Yeah. So CO2 rebreathing’s a way we measure hemoglobin mass in the lab-

[00:49:33] Dr. Mike T Nelson: Oh,

[00:49:34] Jonah Rosner: yeah, yeah … um, essentially, so it’s, it’s a way to get hemoglobin.

[00:49:36] Jonah Rosner: So actually, what happened a few years ago, um, riders on the world tour for the, um, cycling, the world tour cycling, like the ones who participate in the Tour de France, were using, well, they were essentially inhaling carbon dioxide or, um, that as well, the CO2 rebreathing. Because what they’ve done consistently over time, it actually leads to more hemoglobin mass.

[00:49:57] Jonah Rosner: Correct. Um, since essentially it’ll give you the body a signal that, okay, there’s this weird stress going on, and to counteract it, similar to how we talk about with heat, I’m gonna make more hemoglobin. So it’s actually funny where people are using that technique on the tour to increase overall hemoglobin, and it got banned as an illegal drug.

[00:50:14] Jonah Rosner: Yeah. But yes, I’ve seen it from that standpoint, and I know that they talk about that from a whole body standpoint as well, potentially some of the effects, but I’m not too familiar with some of the other potential benefits.

[00:50:25] Dr. Mike T Nelson: Yeah, I just started playing with it and it’s, you know, I’ve only done maybe 13 sessions total, kind of split over a fair amount of time, and my HRV score does seem to be a little bit better, not necessarily the next day, but the day after.

[00:50:39] Dr. Mike T Nelson: And one other thing I’ve noticed- Interesting … is that at sub max stuff, my heart rate appears to be a little bit lower. But like even zone four, zone five, if I’m doing it for a prolonged period of time, my heart rate is actually paradoxically higher, but my RPE is lower. Like, I can hit- Interesting … higher percentages of heart rate at a lower RPE, and like the curve goes up steeper, and then it’ll, I can hang out at higher levels of heart…

[00:51:09] Dr. Mike T Nelson: And then my performance was better, too. And I don’t know if that’s because I’m getting better oxygen exchange, like via the Bohr effect at the tissue. Maybe I have more- Yeah … red blood cell mass, but it- Yeah … it’s been consistent over like the higher intensity sessions I’ve done that are in several minutes range.

[00:51:28] Dr. Mike T Nelson: Like the four, four of them I’ve done, that’s been a relatively consistent effect, so I don’t know.

[00:51:35] Jonah Rosner: That is interesting. I definitely would argue, agree. The first thing that comes to mind is like the Bohr effect or those, as you alluded to, um, some of those pressure dynamics. But yeah, I don’t know either as well, but it is interesting, like all these different modalities you could potentially use to alter the heart rate versus perceptual response.

[00:51:52] Jonah Rosner: And I kind of like to think about training load, where you got like the internal cardiovascular sa- response, the mechanical response, the perceptual response, and how we integrate all these things together and manipulate based on the goal of the training session or the block.

[00:52:05] Dr. Mike T Nelson: Yeah, it also was a good reminder to me to remind clients and athletes, if your heart rate is going up and you’re staying at a higher percentage of heart rate, and your output is concomitantly better, don’t freak out because your RPE could be a little bit lower, and that’s actually a benefit.

[00:52:23] Dr. Mike T Nelson: ’Cause I feel like sometimes, and I’m probably guilty of this too, of overemphasizing heart rate too much. And what I’ve been trying to do over the last few years is just, okay, get… I don’t care so much about your heart rate if I don’t know your output. Because to me it’s almost meaningless otherwise. But if your output- You need both

[00:52:40] Dr. Mike T Nelson: went up and your heart rate was higher- Yeah … and this was a high intensity session, that’s good. That’s great. You did better. Exactly.

[00:52:47] Jonah Rosner: That’s the goal. You’re trying to create stress. I think that’s something I’ve found over the years. It’s important that you have a kind of a holistic model, the external versus internal training load to make them more valuable.

[00:52:56] Jonah Rosner: But also at the same time, like heart rate, that’s been one of my big experiences. Especially in today’s age, like with heart rate monitors, you get, gonna get variability from the devices where they might not be accurate depending on how the individual wears them, the type of session. Yep. Um, but then also there’s a lot of things that affect heart rate.

[00:53:11] Jonah Rosner: Caffeine, dehydration- Yep … day-to-day stress. And I think it’s important that you take into account the external workload relative to the RPE. I’m actually probably a bigger fan of RPE than heart rate for a lot of situations. Mm-hmm. And you said to just understand what was the goal of the session, and if you could complete the external work desired, and maybe it was a little harder or a little easier, that- that’s probably not a bad thing, and not to freak out about heart rate.

[00:53:33] Jonah Rosner: ’Cause so many people would say to me, “Oh, my heart rate was too high for this easy run zone two.” But the main goal of these easy runs is to essentially allow you to accumulate volume without hurting your recovery. So if your heart rate was a little higher, but it felt easy and you were fine the next day, I would say it probably doesn’t really matter too much.

[00:53:49] Dr. Mike T Nelson: Yeah. Which I think gets into, you know, people have their zones done once a year ago, and they swear that they’re gonna be the same every single day. And I’m like, but y- so you’re telling me a, a high zone two, zone three… Oh my God, one day I’m magically in zone three and another day I’m in zone two. Like it, physiology is just not that stepwise linear from one to the next.

[00:54:12] Dr. Mike T Nelson: It’s just giving you a- Exactly … rough idea of where you might be at.

[00:54:16] Jonah Rosner: Exactly.

[00:54:18] Dr. Mike T Nelson: Cool. And as we wrap up, like I know you worked in the NFL for many years, and now you work on the other end of the spectrum. How did that happen?

[00:54:27] Jonah Rosner: Yeah. So essentially, probably like a lot of people start off in professional sports, did my time as a sports scientist, NFL, a few of the other professional sports leagues as well.

[00:54:37] Jonah Rosner: And I think you probably get to a point where you don’t wanna work 80 to 90 hours a week, never see your family, and you kind of just wonder what else is out- It’s

[00:54:44] Dr. Mike T Nelson: brutal. I don’t think

[00:54:44] Jonah Rosner: people realize- Oh, it’s crazy … how brutal it is for most of those positions. Yeah. And you’re just like, “Oh, I wonder if there’s anything else out there.

[00:54:50] Jonah Rosner: I would like to see my family more than once a year.” So kind of decided to make the move back home to New York, um, area, see what else is out there. And yeah, I guess I enjoyed like building my own thing, working with a wide variety of athletes now. So I still work with some elite athletes, but now general population as well.

[00:55:05] Jonah Rosner: Work a bit on like the business media side, and just really enjoyed building my own thing and, um, getting more involved with running because that’s a personal project, a passion of mine, and having more free time to pursue some of these passions. So that’s essentially how it happened, and probably as I start building my own thing and being able to learn in the areas I wanted to learn, I just became super passionate about the private sector.

[00:55:27] Dr. Mike T Nelson: That’s awesome. Any good NFL stories? I, I don’t think… Until people have- Man … seen a 6’6”

[00:55:34] Jonah Rosner: Yes, I think sometimes- …

[00:55:35] Dr. Mike T Nelson: 330

[00:55:36] Jonah Rosner: pound- Yeah …

[00:55:36] Dr. Mike T Nelson: athlete move in person, it, it’s hard to

[00:55:39] Jonah Rosner: explain- I mean- …

[00:55:39] Dr. Mike T Nelson: what’s going on.

[00:55:40] Jonah Rosner: I, I just remember some of these offensive linemen who, exactly as you alluded to, were like 6’7”, 300, 350 pounds, and just could probably beat me in a 30-yard sprint, not even close.

[00:55:51] Jonah Rosner: Yeah. Or like dunk a basketball jump, and you just realize that some of these ath- the athleticism some of these athletes possess is just unbelievable

[00:56:01] Dr. Mike T Nelson: Yeah. And that’s been kind of the argument, I think, from the Olympic weightlifting community, uh, community in the US is that we have all these other places that these high-level freaky athletes can go play for millions of dollars that other countries may not have those opportunities.

[00:56:16] Dr. Mike T Nelson: And so if we could extract some of them, maybe we would do better in Olympic weightlifting or not, I don’t know. But there’s definitely a lot of just insane ability in high-level sports, like, no question. A lot of them, it’s even sometimes in spite of their nutrition and their training too.

[00:56:35] Jonah Rosner: I think a lot of times it’s in spite of it.

[00:56:38] Jonah Rosner: It’s like you kind of just realize it’s the last 1% of their genetic gifts who really would carry them.

[00:56:44] Dr. Mike T Nelson: What are your thoughts about, do you think genetic engineering will be a thing coming more in the future? I mean, there’s

[00:56:52] Jonah Rosner: all sorts of- I, it’s interesting …

[00:56:53] Dr. Mike T Nelson: talk about

[00:56:54] Jonah Rosner: changes now. I don’t- definitely not my area of expertise, but I think it’s definitely gonna be out there.

[00:56:59] Jonah Rosner: Yeah, I don’t know enough about it, but I definitely think it’s possible.

[00:57:03] Dr. Mike T Nelson: Yeah. There’s been some rumors that other countries for their Olympic weightlifting team may have already be doing it, because as of now, there’s no way to know yay or nay, you know? So, and athletes- Yeah … historically will do all sorts of crazy stuff.

[00:57:21] Jonah Rosner: Yeah. Yeah, exactly. So that’s been my takeaway as well.

[00:57:27] Dr. Mike T Nelson: Awesome. La- last two questions. I know you mentioned, uh, some of the triphasic stuff. Do you use that with your endurance athletes, even though that’s … I know it’s typically reserved- You know, I- … for strength and power, but I could make an argument for tissue adaptations and things like that possibly.

[00:57:44] Jonah Rosner: Yeah. I don’t know how much I use it in general anymore. Um, I definitely use more with some of the endurance athletes, for those who are well-trained, you’re familiar with the weight room. Probably some of the principles where maybe we’ll do overload eccentrics, where we actually really overload the eccentric part of specific lifts that I think are critical for them.

[00:58:01] Jonah Rosner: And we’ll do a lot of, um, isometrics in key positions that are heavy, not because I think that there potentially is anything super novel to the isometrics. I think, like, heavy loading too I think could give you a lot of the similar tendon adaptations and p- beneficial tissue adaptations. But we do do a lot of things like calf isometrics.

[00:58:22] Jonah Rosner: We know the calf tends to behave isometrically during distance running as well. So just to mimic that and get it in a joint angle where we know that people, um, tend to spend in distance running, so we’re very specific to the sport. And also it tends to potentially not lead to as much soreness, and so they like that as well.

[00:58:41] Jonah Rosner: So we’ll take a lot of principles where overload eccentrics, some isometrics, because the calf does tend to behave isometrically, and be able to load it super heavy, which is potentially good for the Achilles tendon, which is good for them, um, without a ton of tissue, as much tissue stress maybe

[00:58:57] Dr. Mike T Nelson: Anything you would recommend for Achilles tendon risk reduction?

[00:59:03] Dr. Mike T Nelson: Because that’s one thing I’ve noticed even maybe I’ll blame the resurgence of pickleball or whatever, but there’s just

[00:59:09] Jonah Rosner: more and more- It’s definitely pickleball …

[00:59:11] Dr. Mike T Nelson: injuries

[00:59:12] Jonah Rosner: now-

[00:59:12] Dr. Mike T Nelson: Yeah … of just-

[00:59:13] Jonah Rosner: I think… Yeah. Not my area of expertise, but tendons 101 is just like progressive training load. I think a lot of where people get in trouble with tendons is too much too soon, especially at higher intensities or overall mechanical loading.

[00:59:24] Jonah Rosner: So go from 0 to 100 and they’re running, they sign up for a marathon, they go from 0 miles to 20 miles a week, and all of a sudden it’s the tendons are taking on this higher intensity stress they’re not used to. So I would say a progressive training plan where you make sure the tendon has time to recover and you’re slowly progressing the overall load.

[00:59:40] Jonah Rosner: But then I do think this is where you get into some of the things like, um, some of the gym work. We know that running, um, probably over time will increase tendon stiffness, but it may not be as potent of a stimulus as potentially heavier lifting where you need some of that heavier slow movement, whether it’s the fluid dynamics of the tendon or the mechanical receptors of the tendon, just need a little bit more time under load to increase the overall stiffness.

[01:00:04] Jonah Rosner: And so when we increase the stiffness of a tendon, what happen is it experiences less strain. So a stiffer tendon is gonna stretch less with every step, and a tendon that stretches less experiences less strain, so probably will be exposed to less mechanical damage. And we know one of the best ways to improve a tendon’s stiffness is heavy work in the gym, as I said, because from, uh, the cells will potentially sense that increased stiffness over time.

[01:00:27] Jonah Rosner: And so I think just creating a more robust stiffer tendon can help protect, uh, from some of the demands of distance running as well.

[01:00:34] Dr. Mike T Nelson: Are you a fan of, like, the 20, 30-second isometric work, like from Keith Barr’s stuff? I know that’s

[01:00:39] Jonah Rosner: also- Yeah, I think it’s- …

[01:00:40] Dr. Mike T Nelson: controversial …

[01:00:41] Jonah Rosner: it’s, it’s definitely controversial.

[01:00:42] Jonah Rosner: I know Keith says that you get, like, that stress relaxation after 20 to 30 seconds. I think I would argue, I don’t know if you need 20 to 30 seconds. I think if you get, like, four to five seconds hold but heavier, that’s gonna do just as well, and it’s more just about getting enough strain, so heavy load through the tendon for a few seconds.

[01:00:59] Jonah Rosner: I don’t know how much I believe in, like, the 20 to 30-second holds anymore, where it’s more about getting enough, um, mechanical, um, strain through the tissue, um, for a few seconds.

[01:01:08] Dr. Mike T Nelson: Very cool. Anything else I didn’t ask you that I should have asked you, or something you’re like, “Oh- No,

[01:01:14] Jonah Rosner: I

[01:01:14] Dr. Mike T Nelson: think- … this thing is so cool”?

[01:01:16] Jonah Rosner: I think this was excellent. I mean, this is pretty much most of the stuff I, I like to nerd out about, and obviously a big fan of your work, so it’s great just to kinda nerd out about some of this stuff.

[01:01:26] Dr. Mike T Nelson: Awesome. Yeah, thank you so much for answering all my crazy questions and stuff too. I think that’s, uh, definitely a good background and gives people plenty of options and at least some rationale to think their way through it.

[01:01:40] Dr. Mike T Nelson: ’Cause I think, like I’m sure you’d probably agree, there’s too many, what I call, like, parrots in the industry. Everybody just parrots what somebody else says, and then they try to apply it to something else that makes no sense whatsoever because they didn’t understand the concept behind it or what was actually going on, and then they’re not measuring outputs.

[01:01:59] Dr. Mike T Nelson: So the things they’re doing, they’re not really sure if they’re actually paradoxically beneficial or not. It’s like, oh, so-and-so said just to do this, or just do zone two all the time, or only do high-intensity stuff. It’s… I just, I like that there’s more thought going in because you can design your own experiment then and see, oh, did this move the needle?

[01:02:19] Dr. Mike T Nelson: Did it not? Again, you may not know for sure that was the reason, but at least it gives you a way to kinda iterate your way forward through things.

[01:02:27] Jonah Rosner: Exactly. Exactly. Couldn’t agree more.

[01:02:30] Dr. Mike T Nelson: Awesome. And, uh, tell us where people can find you. I know you’ve got tons of great stuff on Instagram

[01:02:34] Jonah Rosner: and- Yeah … everywhere else.

[01:02:35] Jonah Rosner: I would say my main medium right now is social media, Instagram, so rajnarperformance, and I can send you a link, and then also my newsletter, Marathon Science, um, where I deep dive in. I’ll send you a link too. I have a lot of free resources about the stuff I talked about, which I could just send the links for, like, some of the strength stuff for runners, some of the, um, endurance guides that we recommend, some of the zone two versus HIIT.

[01:02:55] Jonah Rosner: So I’ll definitely send them over to you as well.

[01:02:58] Dr. Mike T Nelson: Awesome. Yeah, I would highly recommend people check out that stuff. And, uh, thank you so much for all your time here today. I really appreciate it.

[01:03:05] Jonah Rosner: Yeah, thank you for having me.

[01:03:07] Dr. Mike T Nelson: Thank you.