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Balancing Intensity: The Science Behind the 80-20 Training Principle
Episode 1322nd February 2024 • The Athlete's Compass • Athletica
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In this episode of the Athletes Compass podcast, hosts Paul Warloski, Marjaana Rakai, and Dr. Paul Laursen dive into the 80-20 training model, a popular method for organizing training time among endurance athletes. They explore the origins of the model, its application in preseason training, and how it can be adapted for different training volumes. The discussion includes insights on the benefits of low-intensity training, the importance of monitoring heart rate, and the role of high-intensity sessions in a balanced training plan.

  • The 80-20 training model suggests that 80% of training should be at low intensity (zones 1 and 2) and 20% at high intensity (zones 4 and 5).
  • Originated by Dr. Steven Seiler, the model is based on observations of elite Norwegian cross-country skiers and their training methods.
  • For athletes with limited training time (8-10 hours per week), the 80-20 model can still be effective, but other training plans may also yield results.
  • Incorporating a small amount of high-intensity training during the base phase can lead to better performance in subsequent build phases.
  • Monitoring heart rate is crucial for ensuring training is conducted at the correct intensity, especially for zone 2 workouts.
  • The 80-20 model is flexible and should be adapted based on individual needs, training volume, and specific race goals.

Transcripts

Paul Warloski (:

Hello and welcome to another episode of the Athletes Compass, where we navigate training, fitness, and health for everyday athletes. This week, we're answering a listener question about the 80-20 tool for organizing your training time. It's a popular and widespread model that suggests that most of your training should be in zone one and two. Remember of our discussion in zones in episode 10, I think.

Paul (:

Thank you.

Paul Warloski (:

and the remainder should be harder efforts in zones four and five or above your, right around your threshold or above. While Dr. Steven Seiler, who is credited with creating the 80-20 model, never intended it for it to be a hard and fast rule, there are now a lot of misunderstandings around the model. So let's dig into what it is and how everyday endurance athletes should use it.

Paul (:

Let's dig into what it is.

Marjaana Rakai (:

And this week we have a listener question from Navin from Texas for age group triathletes with limited training time around eight to 10 hours per week, looking to get faster. And he mentions higher FTP. Is 80-20 the right training method for pre-season? Specifically if early season is focusing on sprints and Olympics where speed is primary over endurance.

Paul (:

This week we have a listening course.

Yeah, that's a great question. So is it optimal? It's a good model in the preseason. One of the things usually in preseason that you want to have is you want to do that aerobic base, no question. So even in the 80-20 model, you're going to be doing the bulk of that.

as building your aerobic base. And what we say, when we're doing that, we say we're building our ability to burn fat as a fuel, we're building the heart's capacity to pump blood to the working muscles. But even having that 20% or even call it five or 10%, you wanna do at least one session per week, potentially two as a little bit harder

kind of work. Now there's research from Rolstad and colleagues that has shown if you do add just a little bit of high intensity in your week during the base phase, you are better off when you start in on the build phases of your program than if you had just done straight aerobic training. So that's just to kind of start there and answer the question.

It's good to still have a little bit of high intensity work in there. Is it optimal? At 8 to 10 hours a week, you could probably get away with a lot of different training plans if I'm honest. You could probably be doing sweet spot training and still get away with it. But you would, if you're stressed, you would run a little bit more of the risk of going towards that overtraining. But a lot of people can still handle that too.

So at those lower training volumes, like eight to 10 hours a week, probably get away with almost anything. Where 80-20 really comes into play is at higher training volumes. When you start moving towards the 15 hours a week plus, and you're still doing too much high intensity work, you're gonna definitely eventually feel that. And that's where...

you're going to start to potentially have too much stress overall. When we do high intensity work, we get very, very stressed. So if you're continuing on with too much sweet spot, too much threshold, too much HIIT you're going to, and then add time onto that, which is training volume, then eventually you get kind of run down. So the 80-20 formula.

ve at ACSM in Seattle back in:

He said, no, this is not the way the elite cross-country skiers that were winning gold medals was doing it. He was observing them. It's like, no, the coaches were not doing it that way. They were not going threshold all the time. They were doing their training easy, steady, the majority of it. And only the key sessions were done quality. But by doing it in that model, you spare yourself so that the hard sessions...

you can just rip the legs off yourself when you kind of go and rip into it. And you get a lot more bang for buck. So it's a, tends to be the better road to Rome. Sorry, long-winded answer there.

Paul Warloski (:

Thanks for watching!

Marjaana Rakai (:

And I think speaking to the Nordic model, it's not just Norwegian, it's Nordic. Because I was a cross-country skier like long, long time ago. And that's what, that's what we did. We, during summertime, which was base training, we would go Nordic walking. So we're walking with our ski poles that are a little bit shorter. And uphill we would walk.

Paul (:

Yes you were.

Marjaana Rakai (:

And then once we crest the uphill, we start running. So we would run on the flats and then uphill we would walk to keep the heart rate low. Yeah, it was, but it takes, it takes some discipline though, which I wasn't that good at. I tended to go into the zone three trap.

Paul (:

I love it. So, there you go.

Yeah, but so many people find that, right? And even when they're like the classic example is people coming into Athletica and they perform the MAF test and they're just they're like, I can't do it. I can't do it this low. It's just my body doesn't work that way. Well, you need to slow down even further, right? That's what Phil Maffetone would say. He said, well, you actually just need to walk then like you were sort of saying, like if you want it, if you want this to work, you've got to kind of keep that stress really low.

Marjaana Rakai (:

Mmm.

Mm-hmm.

Yeah.

Paul (:

to perform that way and your body will adapt and you won't be walking forever, right? Eventually, eventually you'll start to be able to move faster at those lower exercise intensities because fat metabolism will take the place of the carb burning stuff that you're currently doing. That's why your heart rate's so high.

Marjaana Rakai (:

Mm-hmm. And I would like to echo a little bit about the MAF tests because a lot of people are asking what's the point of these MAF tests and the point is to look at your progress over time, like if you commit to Athletica program, you start with the test week, um, take a note of your MAF tests, if you're doing it running, what is the pace over those 5Ks

8Ks whichever version of MAF test you're doing, and then retest over time. And you can see if your zone two work has been done slow enough, easy enough, because you'll be running a lot faster at that same intensity. That's my experience.

Paul (:

Yes, totally. And same with the power outputs as well on the bike. Like you can see the same thing, right? And this is that MAF power is that's typically kind of top of zone two, bottom of zone three. That's typically where we're trying to kind of pinpoint, right? But Ironman pace, right? So anyone out there that's gunning for an Ironman or a half Ironman, it's like, you know, really helps to have a, you know, working on your ability at that MAF

Marjaana Rakai (:

Hmm, yeah.

Paul Warloski (:

So Marjaana, how do you think and how do you as a coach suggest to athletes to practically implement this 80-20 model into their training schedules, especially if it's a well-rounded health-based training plan that includes strength training, cross-training, recovery and

Marjaana Rakai (:

Uh, well, Paul kind of already answered that. Like if you're in a low volume, uh, keep it simple. Like if you're training 10 sessions per week, one or two could be high intensity and then you add the strength. It doesn't, that don't overcomplicate things. It doesn't have to be that complicated. Like, of course you could go into a rabbit hole and start, you know, counting minutes and, you know, making sure that you're doing 80, 20, but, uh,

It doesn't have to be that complicated.

Paul Warloski (:

So four of five, eight of 10 sessions in general are easy kind of endurance sessions.

Marjaana Rakai (:

Yeah. Like if you're doing 10, do one VO2 max, do one like around threshold, strength training that leaves you seven easier sessions.

Paul Warloski (:

Hmm. Okay.

Paul (:

Yep. And I mean, if you're a triathlete and you're doing those two, right, you might want, you know, a high intensity running session, you might want a high intensity bike session. And then again, we're talking kind of the base phase as well here too, right. So yeah, and space, space them out in the week as well. So you feel kind of kind of recovered or if you if you I mean, there's this whole thing called the priming effect to right, you can actually have them back to back as well. That might not might suit you suit you. But yeah, good, good to get one or two in the week for sure. Yeah.

Marjaana Rakai (:

Hmm.

So I've been doing strength followed by VO2 max bike sessions and those been really good for me. But I'm used to strength training. Some might feel that their legs are zapped if they do strength before bike. So they might want to switch over, do the bike first and then do the strength after.

Paul (:

Yeah. And that's, we mentioned that in the Erin Carson strength training podcast as well. Um, you know, in her experience, she tends to find that, um, that priming effect is best. So it's like, just like Marjaana said, so it'd be like a morning session might be a, you know, a weight session or, or high intensity session. And then the, the afternoon session is also high intensity, but it's, um, and it would be the alternate one. And, um, yeah. So in experienced athletes, that tends to be the.

a really nice formula. We showed that in a Jess Bush's PhD study as well on the New Zealand elite kayak team where we actually looked at what was the better output for these elite kayakers on the Olympic program. Just like Marjaana said, they had better power outputs on the kayak ergometer when they did their strength training in the morning.

versus when they did it the next day. So the next day they felt, they kind of felt flat after the sleep for whatever reason. There was like, yeah, they were still kind of in that sleep inertia and it was like, they couldn't get G'd up for it as much as if it was just on the same day.

Paul Warloski (:

I think the other thing with the strength training, you know, I tend to prescribe, you know, hard days and easy days. So if I'm going, if there's going to be, uh, intervals on a day, that's a day that we'll also do strength training. Typically, not always simply to keep it a hard day, hard. Um, and yesterday I tried, I, after listening to the strength training podcast with Aaron Carson, um, I tried the priming.

Marjaana Rakai (:

Mm-hmm.

Paul Warloski (:

effect, but right away I did my intervals and then right away went to the gym. That did not work. I was tired. And although, you know, we're obviously not trained to be bodybuilders. The key is to develop that sense of, of fatigue. And that's what we're trying to do in the gym is, um, strengthen the muscles by building additional fatigue.

Marjaana Rakai (:

Hahaha

Paul (:

Hehe

Paul Warloski (:

and move in different directions so that we are building full body strength. I'm also reading right now Alan Cousins' new book and he talks a lot about how to monitor the endurance sessions, the 80% or the majority of what, and he talks about 60 to 75% of your max heart rate is kind of your zone for endurance. How...

How would you recommend both of you athletes monitor their intensity to make sure that they're still staying in the right zones?

Paul (:

Well, I think, I think Athletica does a pretty good job of that, where the zones are calibrated as best we can. We're going to get better with that. We're working on a new innovation right now around the power profiling and the pace profiling that is going to make the zone calibrations even more individual. At the moment, when you use programs like TrainingPeaks and others, and even Athletica today as we speak.

.:

fiber types, how resilient those muscles are, your durability in them, your anaerobic power and speed reserve, how much fast twitch muscle fibers that you have. And again, we were just speaking offline about the genius developers that we have at Athletica. Well, they've figured out a way where we can actually use that power and pace profile to get even closer to what your

speed your zones should be on for both pace and heart rate. So watch out for that kind of coming. And yeah, but that's yeah, I hope that I answered your question there.

Paul Warloski (:

Mm-hmm. Heart rate, power, pace, what's the best ways of monitoring, especially for zone two?

Paul (:

Well, I mean, heart rate for yeah, for sure heart rate like you. That's the best one, right? So it's like, go at your heart rate for zone two, we this is, this is the smart coach option on Athletica. So if you go to your settings, and you'll have you'll be able to actually push your workout prescription to your Garmin unit if you happen to be using Garmin, which most are

and you'll actually get that pace prescribed in zone two via, if you use the smart coach, you'll use heart rate. It'll give you the heart rate range that you should be at. And that's best practice because, you know, if you are, say the heat is out, it's really hot, or say you're at altitude, or say you're fatigued, who knows what issue is gonna cause you to slow down, then...

you know, your cardiovascular system connected to your nervous system is just gonna down-regulate the pace or the power. And that's good because then we get the stress right by doing that. So yeah, so go at your heart rate for zone two training is best practice. If you are getting a prescription to hold this pace or hold this power, what's gonna happen, right? You can imagine if you're off on the day or the prescription's wrong,

cardiac drift and that rise in heart rate, which is called, is termed in exercise physiology, cardiac drift. It's an indicator that the stress is going out of whack and you're drifting up into zone three, which is classic problem for, you know, why we run into endurance training, just like drifting into mid zone. I did it all in my training life. So don't do what I did and don't do what Marjaana did. I see her giggling here as well because she knows better as well now too.

Paul Warloski (:

Thanks for watching!

Paul (:

Right, MJ?

Marjaana Rakai (:

Totally. Yeah. A couple of things that you can use together with your heart rate and your feel is if you're able to nose breathe. Because if you're nose breathing, you can't really go too hard because it becomes impossible to nose breathe. Especially, well, at least for me, it took a while to learn how to nose breathe while I'm running easy, but it's possible to learn.

Paul (:

Mm-hmm.

Marjaana Rakai (:

And then chatting full sentences. This way a slower running partner is so good to have because of that. You can, you know, it keeps you in that zone 2 Uh, and then, you know, the feel to ask yourself how, if I was to rate how I'm going right now, is it two, within two, three, maybe four at the end out of 10?

Like, could I keep going for like six hours at this effort? That should be an indicator that you're doing it slow enough or easy enough.

Paul (:

Totally.

Yeah, awesome advice, coach.

Paul Warloski (:

I always tell my athletes they can talk about anything with somebody except for politics or religion. And those two things might get a little, it might get a little too heated for zone two. So, don't go there, no, no. What are some of the specific benefits that athletes could expect from an 80-20 kind of model, such as improved endurance or faster recovery or reduced risk of injury? What are some benefits that might happen?

Marjaana Rakai (:

Thank you.

Ha ha ha! True!

Paul (:

Don't go there, don't go there.

I think you nailed them, Paul. So yeah, you are working on your endurance, your resiliency, and yeah, you're building the slow twitch muscle fiber resiliency, you're building your ability to burn fat as a fuel, which we know is far more efficient than the alternate burning

carbohydrates with larger motor units. And yeah, the higher we can kind of get that level, the more everything is just easy. And just to kind of go into the metabolic machine, when you look at the production, what actually happens as a byproduct of a burning of fat versus a burning of sugar. When you burn sugar, the byproduct is more of a blood lactic.

response, pyruvate to lactate, including hydrogen ions, so you become like more of an acidic kind of medium versus burning of fat. The only byproduct that you get from the burning of fat, like a pyruvic acid, is water and carbon dioxide. You just easily breathe out the carbon dioxide, water just goes back into the system. So it's like this, you know.

Yeah, just energy efficiency. Like you're just such an efficient human being and you won't be out of breath. You'll be in homeostasis. And yeah, and it's like all those various different things. So you want that level as high as you can kind of go because then your all-day pace is easy. And if you wanna turn on the gas later, then you can do that. You can always kind of dip back into that sugar burning.

system but you're sparing it only for the end when you need the punch when you need to drive the throttle forward but yeah

Marjaana Rakai (:

I used to do my long rides and sing this silly song about building mitochondria. And if I...

Paul (:

How does it go? Sing it out. Come on. Give it to us. Oh, come on.

Paul Warloski (:

I was gonna say you've gotta share it now.

Marjaana Rakai (:

I can't do that. I can't do that. I'll sing it if we ever ride together then I'll sing it.

But so zone two builds mitochondria, right? And then a higher intensity makes the mitochondria work more efficiently. Is this physiologically correct way to think of it?

Paul (:

Well, I'm not actually sure. When I think from a cell signaling process, if I go into my little test tube world, there's kind of different signals. Calcium, chelmodulin, kinase is in this slow twitch, long duration area. And then the high intensity stuff is this AMPK signal. And they all meet in the middle and cause the same. They connect.

PGC1 alpha signal that builds the mitochondria. That's kind of what works. You can kind of get the best, you can get, you can hit the mitochondria button from either side. You can hit it from the calcium long distance stuff, or you can hit it from the AMPK high intensity stuff. Right, if you know that. I think you know which schematic I'm kind of talking about, Marjaana. But so yeah, you, I don't really know if there's an efficiency versus a number kind of thing in mind. I think they all kind of work.

Marjaana Rakai (:

Mm-hmm.

Mm-hmm.

Yeah, yeah, yeah.

Paul Warloski (:

Hmm.

Paul (:

towards building that mitochondria at the end of the day, but one does it kind of with low stress and the other one does it with high stress and both kind of, both roads emerge and merged towards the middle to give that same output. But you're always balancing that ability to adapt the system and build the mitochondria with the ability to keep your stress low because remember, it's the consistency of that signaling that you wanna hit

Marjaana Rakai (:

Mm-hmm.

Mm-hmm.

Paul (:

And if you're doing too much of the AMPK high intensity stuff, then you might be putting your putting yourself at risk of missing tomorrow's session because you haven't slept well and you don't feel good and you whatever you become run down it you know lowers your immune response all these various different things who knows what it is injury lots of ways that it can derail us.

Marjaana Rakai (:

Mm-hmm.

Paul (:

Yeah, that's why 80% is down around that low intensity stuff.

Marjaana Rakai (:

And...

Oh, forgot what I was going to say, but, um, I find like when I, I'm on a build phase now or a specific phase, I have three hard sessions, a row, a row. Like Thursdays I'm pretty beat because I've had a VO2 max on Wednesdays. And then I have hard swim Thursday. And I think there's a running HIIT session.

And I'm absolutely just knackered after that. So, uh, Fridays need to be easy for me. Um, but if I weren't getting better at listening to my body signals, I would definitely, uh, overreach or plateau. And I think one of the benefits of 80 20 is that you avoid that.

pesky plateau, like you feel like you're doing everything you're doing, all that HIIT sessions, you know, like, and you're not getting any better. And that speaks to the, you know, parasympathetic stimulation that zone two is so good at.

Paul (:

Yeah, and you know, Marjaana, you're causing me to reflect nicely on the conference that I just gave, the presentation I just gave at Endurance Exchange, and the topic was, it wasn't exactly this topic, but it was highly related. It was the topic of heart rate variability. Now, if you're following Athletica, you'll notice that we just released this feature of heart rate variability. If you're using the Garmin system, we'll be adding other heart rate variability markers in the future, but

For now, if you look on your Athletica profile, you can actually go in to what's called your recovery profile. So it's in your charts. Look in your charts, go down, look at recovery profile, and you can see there your heart rate variability if your Garmin is being worn in the evenings and you've got at least 60 days of capture. You have your heart rate variability in the top panel.

You'll have your heart rate and your sleep in the bottom panel. So this is giving insight into your central nervous system, your autonomic nervous system, your automatic nervous system. And this is where we have both the sympathetic system fight or flight, and we have the parasympathetic system rest and digest. And ultimately, if you are adapting, you should be seeing either plateaus or a rise.

in that heart rate variability number, the seven day rolling average, it should start to be pushing upwards on your chart. That's a sign that you are adapting to the stress. If it's not, if it starts going down in towards negative adaptation, and if the seven day dark blue line rolling average starts going down below your normal value, that's usually an indicator that you've probably got too much high intensity work, too much stress in your life.

This is the cool thing about heart rate variability. It doesn't care what kind of stress that you're getting, whether it's exercise stress or life stress, psychological stress, heat, altitude, battles with your spouse. It just doesn't really care, right? It's like looking at the whole big picture of what your central nervous system is interpreting and it will respond accordingly, all right? And it's measured as an overnight response.

Paul Warloski (:

Yeah.

Paul (:

I'm sure we'll do a whole, this one all over again on one of the episodes, because it's an important topic. And there's some cool stuff coming, but it really relates to the 80-20 principle. That's why we have 80-20 out there, because we know that if we're doing 80-20, it tends to be associated with this favorable heart rate variability response. HRV is a response to the training load. 80-20 is the load itself. So you're getting that 80-20 load training stress.

And then the response to that stress you can see in your heart rate variability number. And now you can see that on Athletica to see how you're tracking. So get it, start to become familiar with that new chart that we've just added literally days ago as we're recording and consider how that is functioning around the load that's being prescribed. And then start to add that to your tool belt as either a coach or athlete.

to know whether you should sort of move things around or not.

Paul Warloski (:

Are there any downsides to 80-20? Anything that athletes should be aware of in terms of possible negative effects?

Paul (:

I wouldn't say it's any negative ones. The only one that first kind of comes to mind, Paul, is that sometimes when we're doing Ironman or Half Ironman, 70.3s or fulls, you tend to want to switch more towards a pure middle approach, which is called. And this is really when you start moving more towards like a 70, 30 kind of approach, where a little bit more high intensity. And specifically the zone three work really starts kind of coming up as you work towards more

Paul Warloski (:

Mm-hmm.

Paul (:

the key races because that's when specific weekend training kind of comes in, especially we see this on Athletica, right, where either zone 3A or zone 3B pieces really start becoming important for those weekend sessions to prepare you for your upcoming event in both the running and the cycling.

Marjaana Rakai (:

I think what Dr. Seiler, like in the beginning, we mentioned that it wasn't meant to be like the whole method wasn't meant to be like 80-20. You just always stick to the 80. Like there's, I'm sure Paul, you're aware of the study by Dr. Rannestad where they studied the most winning female cross-country skier ever. And her, her

training time was like 91% low intensity, but it doesn't look like that over like a whole training year. It might look like 95% in the base season and then it moves towards the 80 or even lower towards, you know, racing season where the volume goes down and intensity goes up. So I think...

One of the mistakes that people do is that they always have to hit the 80-20 and they are going into the rabbit hole and making sure that they do 80% low and then 20% that high.

Paul (:

Yep, I couldn't agree more, Marjaana. And I actually can, I reflect, I'm gonna call out one of my buddies because Dan, so many of you know that Dan Plews and I are good mates and we also had another good mate that we were training with at the time, Rod Siegel. And I'm sure they won't mind me sharing this, but it's like we were out kind of training and Rod was.

Rod was kind of training at these lower exercise intensities, but very into his sports science as we all are. But he was just so into the whole 80-20 thing that at low training volumes that he really didn't, we don't believe that he really got to where he could have because he just kind of, you know, sometimes you just have to, you do have to train a little bit hard kind of thing. You do have to kind of go out of that. So don't be so wound up in these.

just these 80, 20 numbers, so anal retentive that you're afraid to go 70, 30, or even 60, 40 if it's just even for a short while. It's just, yeah, you're splitting hairs kind of thing. Go with the flow a little bit more. These are general rules and they're better sort of hindsight rules where it's like you reflect over it.

Because you use the tools and the monitoring process to kind of say, oh, that went really well. That went not so good. Whatever it is, right? But just reflect on it. That's why the data is there. And then, but don't go crazy with it. I think it's better to be more loose and well-rounded around the whole approach.

Paul Warloski (:

Thank you.

Marjaana Rakai (:

Be a rebel sometimes.

Paul Warloski (:

Hahaha!

Paul (:

Exactly. 100%. Nice.

Paul Warloski (:

So it's a model, not a rule. Yeah. So what advice would we want to give someone who is just starting out? Would they want to do an 80-20? Is that a good guideline for them when they're setting up their training programs? So we're talking about somebody who's either off the couch or just getting started with more structured training.

Paul (:

Yeah, context everything, but I think generally you're gonna start easy. So we wanna walk before we run, right? Like just, yeah, even just get, just getting moving is the first goal, right? Just, and we do have some, you know, some low intensity run programs. Say for example, if you're starting out on the 5K, these are in the base period, we're just running. We're just building up our run training volume.

So train to train kind of thing is the whole philosophy. And then once you've done a few weeks, well, maybe you've got now, maybe now you wanna experience a little bit of exercise intensity and just do a little bit to sort of start there. So it's, I think if you're just getting off the couch we're slow to build up to that 80-20 rule. We wanna just work on the low intensity sort of stuff first and get the motor patterns moving.

The resiliency and the muscles don't want to be injury. We don't want to have any injuries. Want to be injury free. Health is first, right? So get there sort of slowly. And then once you're going and once you're moving after three to four or five weeks, then time to play around with the intensity a bit.

Paul Warloski (:

So our original question was, is the 80-20 the right training method for the preseason? And we're pretty much saying that, you know, 80-20 is, you know, doing 80% of our training in zone one and zone two, and 20 more challenging zones seems to be an effective guideline, to organize our training for higher volumes, especially. For lower volumes, other models can work too.

realize that heart rate monitors and monitoring your heart rate is really the best way of getting the zone two training right to get our stress right. Nose breathing is also a really good tool to stay in that zone two. And the third thing that, third way of answering this question is that doing tempo or sweet spot is not wrong in an 80-20 model. In fact, we need that kind of training for our race prep.

It simply adds more stress to our system that we need to make sure we're recovering from. And we need to consistently signal that those adaptations are happening. And the most important workout is tomorrow's workout. That is all for this week. Thank you for listening and join us next week when we dig into the recent popularity of this zone two training that we're talking about, but more specifically why it's so effective in building health and fitness.

For Marjaana Rakai, Dr. Paul Laursen I'm Paul Wurlowski, and this has been the Athletes Compass podcast. Thanks

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