[Music]

Welcome to the Huberman Lab Guest Series, where I and an expert guest discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine.

Today's episode is the fifth in a six-episode series on fitness, exercise, and performance. Today's episode is all about recovery—that is, how to maximize your recovery to achieve your fitness, exercise, and performance goals, and how to avoid overtraining.

Dr. Andy Galpin, great to be back! Today we're discussing recovery, and I'm very excited to have this discussion because, as we know, despite the fact that different types of exercise can be used to trigger different types of adaptation—such as increased long-distance endurance, anaerobic capacity, strength, hypertrophy, etc.—the workouts themselves are not actually when the progress occurs.

When the adaptation occurs is extremely interesting to me because it parallels what we see with so-called neuroplasticity, which is the nervous system's ability to change in response to experience. We sit down to learn something, we experience something, and that is the trigger for rewiring of the nervous system. But the actual rewiring occurs away from the experience or the learning.

So, too, in fitness and exercise, recovery is where the real results actually emerge, where we get better. I'd love for you to explain what recovery really is, the different types of recovery, and certainly different ways to enhance recovery.

I'd also love for you to explain whether or not there are ways that people can become better at recovering. Because if indeed recovery is when progress emerges, when we get better, then anything that supports our recovery and gets us better at recovering ought to increase our rate and our degree of progress.

Absolutely, you nailed it in the description. What people really want is some sort of change, whether we're talking athletes or the general population. This change is some sort of improvement in muscle function, reduction in body fat, higher functioning metabolism, whatever the case is.

And the only way that happens is we talk about the equation of stress causing adaptation. But as you alluded to, the piece in the middle is only if you can recover from it. So the game we're playing here is we all agree we want more adaptation. That means we need to bring more stress into the system, but we then have to ensure that our recovery outpaces the stress input, or else no adaptation will occur.

In fact, what happens is you will actually be in a negative spot and start going backwards. So what I would love to do is talk about how we've handled this. I've had a decent amount of experience here. I was fortunate enough to do my master's degree in the laboratory of a gentleman named Andy Fry, who's an NCAA Lifetime Achievement Award winner, and he studied, in large part, recovery, overtraining, overuse, overload, and a lot of areas.

In addition, I've been fortunate enough to work with individuals from high-functioning CEOs and executives who have little time for recovery and high job stress to athletes—in the think of the example of pitchers in Major League Baseball who have to recover in a matter of four days so that they can pitch again at maximum velocity.

So I would love to outline some of the tools, tactics, and strategies that we use for all these individuals, give you some foundational stuff, and I would love to maybe actually cover some things that most people have never heard of—some stuff you may not have access to, some technologies that we use, some biomarkers—and then even a whole bunch of things that are keeping with the theme of your show here, cost-free or extremely low cost.

What I would also like to do is cover nutrition, supplementation, fueling, and hydration, but that's probably going to have to be saved for an additional conversation that we'll do in the next episode.

Yes, so we will absolutely hold a conversation about nutrition and supplementation where you can educate us about all the top-tier stuff all the way down to the fine details.

I do have a question about recovery, and it's one that I think most people are familiar with themselves, which is soreness. We think of it as muscle soreness, but I was trained early on in my scientific career to always question the seemingly obvious.

So a couple of questions about soreness. First of all, what does soreness really reflect? Is it really muscle soreness? It feels like it's in the muscles, but what other organ systems, tissues, and cell types does it involve?

And then I'm particularly interested in this concept or this experience that many of us, including myself, have had, which is delayed onset muscle soreness. Why would it be that when we are less in shape or when we perform a movement that is extremely novel to us, the soreness seems to arrive after a reasonable delay of maybe even a day? You know, we're fine the next day, but 48 hours later we are exceedingly sore.

And as we get more fit or more familiar with the movement, the soreness seems to arrive earlier. So I realize I just asked you about three questions or more. First of all, what is muscle soreness at a cellular level? Which cells, which organ systems, and so forth? What does it mean if we are sore?

That's something I know we'll get into a little bit later. And then why the delayed onset muscle soreness? It's actually one question, so it's totally fine you answered all three because I'm going to actually answer number three, which will answer number two, which will actually answer number one.

I'd love to tell you that I set it up that way intentionally, but I'm just happy to hear that where I was unable to be concise, you were able to be concise. Thank you!

Yeah, we are still learning a lot about this area. It's actually really difficult to perform these studies. Anytime you ask a question about something like pain or soreness, you're immediately talking about perception. There is obviously a physical component to that, but there's also perception, and so teasing those things out is extraordinarily challenging.

That said, there has been a lot of work in this area. In fact, you may have a show already out on pain, or maybe one's coming down the road. We did an episode on pain a while ago, but it's definitely time to revisit that literature.

I also have some amazing colleagues at Stanford who work on pain, both from the cellular and molecular side, but also from the psychological side about how our understanding of pain and what we believe about pain shapes the experience of pain and pain relief. Amazing! That stuff is incredibly important, and I'm glad we flagged that.

Maybe we'll just call that good for now; they can come back later for another one of your shows.

So that being said, why does it happen 24 to 48 hours after you exercise? Well, that actually should give you some clues into what's happening.

The traditional dogma of delayed onset muscle soreness, which is what this is called, is that it is a result of quote-unquote micro-tears in the muscle. So you can sort of think, "I challenged the muscle; there were some small tears in there, and I'm feeling the result of that."

Well, in fact, that certainly does happen, and it can happen. That is not what's explaining your muscle soreness. In fact, you can be quite sore from exercise and have no measurable amount of muscle damage.

Much like anything else, when we're in this idea of pain, it's not a one-to-one explanation. There are multiple factors that are probably causing your perception of pain. Muscle damage can be one of them; it is not the only one, and it is probably, in my opinion—though this is yet to be shown definitively—probably not even the leading cause of it.

So what's actually happening? Well, the reason it's taking you 24 to 48 hours is you can actually find various papers, literature reviews dating back a number of years now, over a decade, that show these wonderful curves of an inflammatory and immune response.

We don't need to necessarily go through the entire physiology right now, but effectively what's happening is those things have a little bit of a time delay. Some of those steps happen immediately, like right when the exercise is there, and then some of them are delayed six to 24 to 48 hours.

If you know a little bit about this physiology, you have a combination of neutrophils and macrophages and a bunch of things happening, and this has a time sequence. So what happens is by the time we get to this 24 to 48 hour window, now the muscle soreness kicks in.

Which, wait a minute, if this was a result of my muscles being torn and that happened immediately, wouldn't that pain start immediately? Well, the answer is it would. And so that is your first clue that that's not responsible for it.

When we look at that immune response and we see that that is actually peak 24 to 48 hours later, and then that's the same time the pain kicked in, that's cluing you into the problem.

So we have this immune response happening and inflammation, and then all of a sudden we start getting fluid accumulation. And now there are what are called nociceptors, and you're probably very familiar with these. These are pain receptors.

What's actually interesting is we don't necessarily know a lot of information about how many pain receptors are in muscle. They're not really in the belly. In fact, this is why I can perform my muscle biopsies, and they don't really hurt.

You mean in the belly of the muscle, correct?

Yeah, we do have pressure sensors, though. And so if you change the volume of the tissue, you will respond to that very, very quickly.

So by enhancing swelling in the actual muscle, that is immediately putting pressure on those pressure receptors, if you will. That's the signal.

So what's probably happening here—and I just hate to give you another bone—but a lot of delayed onset muscle soreness is probably just a neural feedback loop rather than it is actual muscle damage.

Yeah, makes a lot of sense. There's a lot of interactions between the types of neurons that control touch sensation and pain sensation and itch sensation. In fact, a lot of people kind of collapse itch and pain together. You know, that's something painful and it itches is a familiar thing for people—mosquito bites and such.

And of course, there's the classic gate theory of pain, which people will be familiar with. And then I'll explain why I'm explaining this, which is if you, you know, something hurts—you bonk your knee or you stub your toe—we tend to grab that body part and try and rub it.

Totally! And that rubbing is not a coincidental thing. It activates a set of touch sensors that respond to kind of broad, dull touch, and that actively inhibits, through the release of an inhibitory neurotransmitter, the fibers that control the pain signal.

So anytime we rub a, you know, like a charley horse in our leg or we stub our toe and we wince and then we grab the toe and we kind of like squeeze it a little bit, that's actually deactivating or partially inactivating the pain mechanism.

So the idea that a swelling response would then trigger a neural response that would recruit the pain receptor response here—I’m using broad brush strokes here to explain this—makes very good sense to me.

Now, and only now that you've explained how this process works, I can actually even add more to that. So if you remember how muscles work, we have to have some sort of signal from the nervous system that has to actually go in and tell the muscle to contract.

Well, remember a few episodes ago we covered the physiology here of what's called a motor unit. Okay? Well, what I didn't explain to are called muscle spindles.

And we have talked about proprioception in an episode before as well, but we never tied this picture together. So let me walk you through that really quickly, and it's going to tie this loop into a nice bow.

So what happens is this motor unit is coming in from what's called an alpha motor neuron, and that's going to be innervating your muscle fibers, and that's going to tell the muscle fibers to contract. Those are typically spread out throughout all sides of the muscle—interior, exterior, all over.

On the outside, though, there is another type of muscle called a muscle spindle. Now, these are non-contractile, so they don't have that actin and myosin and they don't produce force. They are responsive; they are proprioceptive.

So what that means is they sense stretch. And this is why, for example, if you were to stretch a hamstring, stretch any muscle group, it doesn't really matter, or muscle, its innate response is to fire back to close that distance.

And this is what keeps you from, say, if you're leaning to the right. You can imagine that the example we give is if you're standing on one foot and you start swaying to the right.

All right, let's say you're standing on your right foot, and this makes this easier for folks, and you start swaying to the right like you're going to fall on your right ear. Your right ear will hit the ground. The inside of your right calf muscle will start being stretched; the outside will start being compressed.

Right? So the stretch on the inside of the right calf muscle will sense that stretch, and it will respond by contracting. That pulls you back to the middle and stops you from falling. That's proprioception.

And muscle spindles send stretch and tell you to contract. The way that they work is through gamma motor neurons. And so these are sensory things.

So what's happening is, unlike when you tell your muscle to contract, it goes alpha to the muscle to contract. These muscle spindles work such that it is, "Oh, I've been stretched," send a signal back to some central point, typically in the spinal cord.

And we don't actually want to go all the way up to the brain; we've got a time delay. This is why these are subconscious, autonomic, right, versus somatic.

So that gamma is going to go back to the central location and then come back through the alpha motor neurons to tell it to contract. So you have this wonderful mechanism of sensing stretch going back.

Well, one theory that's been put forward regarding muscle damage is that the pressure is actually being applied to those nerve endings of the muscle spindles, and that's actually responsible for the pain signal that's going back and coming up to your brain, and you're registering that as pain rather than it is actually in the contractile units.

So that's a very intriguing idea because it would suggest that stretching muscles in order to alleviate soreness might be the exact incorrect thing to do.

Yeah, now I'm not saying that for sure, for certain. I'm just building off the mechanistic logic that we've laid out here.

Yeah, really, that you've laid out here. There's a more effective principle based on exactly that, which is this is generally why low-level movement is effective at reducing acute soreness.

Because that's low-level contraction of the muscles, and it can get tissue out and get fluid out.

Wow, you're literally pumping it out of the cell!

Yes! And in our previous episode, where we were talking about programming or using the WOD, but let's be fair here, where you were educating us, including me, and the audience about different structures for programming exercise for specific adaptations, etc.—the month, week, year scales, etc.—we had a brief discussion about the fact that if one trains legs very hard with resistance training, you know, some heavy squatting or deadlifting, and there's some soreness, that oftentimes doing some quote-unquote lighter cardio or some low-impact work the next day or any number of different things that involve not high-intensity contractions of the muscles but that do require contractions of the muscles, that it can alleviate soreness more quickly than if one were to simply lie around and, you know, watch Netflix or something.

Yeah, that's exactly right. To go back just a little bit as well, if that's really the case, the question is, like, where is this inflammatory signal coming from?

And while there's much to be learned there, there is a little bit of information right now that suggests it's potentially coming from free radicals released from the mitochondria. Again, that may or may not hold up as more research comes; I'm not sure.

But if you remember back to our conversation on endurance, we talked about the electron transport chain and aerobic metabolism. And regardless of whether or not you're getting energy from glycolysis or carbohydrates, remember they have to be finished through aerobic metabolism.

So even if you're lifting weights and you're using carbs for your fuel, you have got to finish that metabolism by running it into the mitochondria and performing oxidative metabolism.

As a result of that, that electron transport chain runs. So theoretically, if free radicals—which are hyperreactive oxygen species—basically, they're oxygen molecules that are missing an electron, so that they react

**Work Fantastic**

They do, so it's a challenging field to get really objective data on. There's always going to be a little bit of subjective nature to some of these things. I can tell you anecdotally we've used hot and cold contrasts for a long time with athletes. Some love it, some don't care for it, and everything in between.

So, it's one of those things where I never mandated it. Of course, I can't mandate anything for anyone I work with, but I'm never like, "Hey, are you interested?" Great! You're struggling in this area; you want to try this? You did, and you liked it? Great! You're struggling in this area, and you tried it; you didn't love it? Okay, fine. We'll find other routes.

As we'll get into, there are a lot of ways to enhance recovery. This is only one, and it hasn't even really come down to stopping the problem in the first place. We're just treating symptoms, which is the first line of defense, but you really need to go back and figure out why it's happening to begin with as a solution. These are just different, again, acute symptom management tactics.

One final point about deliberate cold exposure I think is worth mentioning is one of the reasons the shower is effective but not nearly as effective as cold water immersion or immersion in ice up to the neck is simply because of the reason you stated before, which is that most showers are not going to get that cold. You're not going to get down, you know, into the sub-40s.

Also, cold showers haven't really been studied that much. They have, but not nearly as much as immersion. People always ask why. I just think about the challenges of studying cold water exposure in the shower, where you can't really control for how much of the body is covered, whether or not the head stays under, different sizes of bodies, etc.

Whereas when people come into a laboratory, they can get into a cold water tank. We know where the neck is, know where the chin is, and we can make sure that people's arms and legs are underneath. But with a cold shower, sure, you can make everyone face away or toward the shower, but it's really tricky.

For all the variations that were described, that said, would you agree that if one wants to use deliberate cold exposure, that a cold shower is better than nothing and cold immersion in circulating cold water or an ice bath is better than a cold shower?

Yeah, what I would actually say is if you're looking for recovery for muscle soreness, I would say a cold shower is probably doing very little for you because you're not going to be able to get enough cold water onto any muscle besides basically your head.

So maybe you could try a cold bath, and so you at least get some surface area coverage. But yeah, if you want to use a cold shower for all the other awesome reasons, that's totally great. But if you're trying to use that to recover your low back and glutes from being sore from training in a good way, it's probably not going to do much. The immersion would be there.

You actually also hit a sneaky other point, which is if you can't get your water super cold, just make the water move. So if you have jets and stuff you can turn on, anyone who's tried this and you're like, "Okay, I can do a 40-degree bath," awesome. Try 60 when the water's moving, right? Because you break up the thermal layer. Normally, you have a little thin layer of water that you're heating up; you break that up, and it's a whole new world.

Yeah, absolutely. So being very still in the cold water is actually the weaker way to go, correct? You can make your face stoic but make your body circulate some water around you.

As long as we're on this, maybe just one more point about heat. I've certainly used sauna, wet sauna, dry sauna, steam saunas, excuse me, jacuzzi can work pretty well.

Males, if you are looking to conceive in the 60 days following sauna or hot tub use, do realize that both those approaches do severely limit the number of motile sperm substantially. So for people that are not trying to conceive, don't think that this works reliably enough that you could use it as a form of contraception.

Yeah, but for people that are trying to conceive, it really is detrimental to sperm health, right? And so for that reason, some people bring an ice pack and put it on the groin or near the groin when they go in, but which is harder to do in a hot tub than a sauna.

So here we're getting into the fine points, or crude points if you will, pun intended. But the idea is that we wouldn't want anyone to approach these techniques and compromise their other life goals.

I was not allowed anywhere near these things when we were at that stage of life. I'll just say Natasha put an "X" on me hanging out with Lared. So going in? No, for those reasons. She's like, "You're not going in. You're not doing none of this stuff," and I just had to wait.

Heat and sperm have a relationship, but it's not one that's positive for the sperm.

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Are there ways to combine the various types of stimuli that you described for inducing recovery? You talked about breathing-based tools, which, while they could adjust and indeed do adjust oxygen and carbon dioxide ratios, etc., I'm guessing the major effect of those on recovery is going to be neural. It's going to be deliberate calming of the nervous system, more sympathetic-based, you mentioned.

Yeah, most definitely. And then you talked about some movement-based and touch-based approaches, which will circulate blood but also will generate contractions of the muscles.

Yep, right. Which maybe, if indeed, again, it's still speculation, if indeed some of the soreness is due to excessive stretch or swelling at the stretch ends of the muscles, that would make sense.

So, movement and touch, and then thermal. Are there ways to combine these that are more effective or maybe even synergistic?

Yeah, I suppose you could throw on some compression garments, put on a pneumatic compression device, and sit in the sauna while you down-regulate your breath. That would be fine.

Quite honestly, though, you probably don't need to maximize all of them. We were joking; you could probably go for a light swim while regulating your breathing in cold water. You get the compression from the cold water, and you'd be in a good spot.

So you can certainly do that. The reality of it is I generally look for some physical approach and then some holistic approach of the breath work, basically. So I want breath and then something else. If you knock those two things out, you're in a good spot.

So that could be breath while you're in thermal stress, so just controlling and doing the un-regulation stuff. You have to also remember ice is a stressor, and I'll actually show you some data here in a second about how that actually can enhance systemic recovery, although it won't happen in the acute minutes. In fact, it's going to take at least 30 to 60 minutes, and then you'll eventually see a rebound effect.

But acutely, it's going to make you actually more sympathetic, which is going the other direction. Heat can do the opposite, or it can actually drive you up. So it's a little bit dependent upon how you respond, what time of day, and how you're using it.

So in general, I guess combining them is if you need it, depending on what you have, what's available. So perhaps you don't have a sauna, but you can take a hot bath? Great! Maybe you have some percussion device, some tool, and you can use that, but you don't have a sauna? Amazing! Don't have an ice bath? These things.

So I think rather than thinking about an optimal combination of them, I would say just use a couple of the tactics based on what you have and what is easily available in your situation.

I'd love for you to teach us about some of the methods for longer-form recovery as it relates to overreaching and overtraining.

Sure! You want to think about this in a couple of phases. Phase one is to try to prevent it from happening in the first place. In terms of training load, you're going to just go back to our previous episodes where we talk and give you specific instructions for how much to increase your volume and intensity per week, etc.

The other thing you can do then is do some monitoring, and I'll go over some different tools, some cost-free ones as well as some higher technologically demanding ones, to monitor to see if it's actually happening.

And then the third approach here is what if this has already occurred? I figured out I'm so how do I get back out of that hole? So I would like to just sort of tackle these one by one in order and talk about what's happening, what tools you can use, and why they're going to work.

All right, so anytime we're talking about fatigue management here, most people are aware of these terms because if you have any sort of technology, you're probably getting some sort of readiness score or recovery score or strain, depending on which app or watch or tech you have.

You have a little bit of vascular change. If you're in the sport performance world, you might be looking at things again like load or GPS tracking and monitoring, and really all of it is doing the same thing. It's trying to either one, predict a problem is going to happen in the future and then placing restrictions upon you so that you don't run into that situation.

The other thing is possibly doing is identifying a drop in physiology or performance and then saying we need to get you out of this hole. That's really what's happening.

And so when we think of the first one, just imagine a scenario like a mileage limitation, pitch count in baseball. What has happened there is individuals in those fields have looked and said, "Hey, what we notice is people who throw, say, more than 100 pitches in a game tend to start losing effectiveness and increased injury rate."

Therefore, we're predicting the next time you go to play, if you cross that threshold, we start having an increased risk of negative consequences. So therefore, we're going to cap your, in this case, pitching volume at that 100 pitches per game or whatever the case. Same thing with running, etc.

So you could just simply do that, and there's actually really cool data coming out now on sport performance stuff looking at things like IMUs and GPS trackers and trying to identify even position-by-position specific recommendations for how much distance you should cover in a practice in a training session.

So that you can say, "Hey, these positions don't cross this threshold; these positions don't cross this threshold in basketball and tennis and all kinds of things like that." That's not probably extremely applicable to many of the listeners right now, but it is still conveying the idea that if we understand where we break, then we can stop ourselves from getting there in the first place.

The functional example here is just thinking about basic things like where do I start my training program and then how do I progress it? And we've already covered those numbers.

In either case, though, you want to have three markers that you're paying attention to if you're concerned you're getting into an overreaching phase or potentially going to lead to overtraining or you want to get out. It's three unique things.

Number one, we're going to look for some sort of performance metric, right? So this could be your times are going down, your squat numbers, your power is going down, any of these things. So it's got to be an actual performance.

Number two, some sort of physiology. And so I want to see something happening with resting heart rate, some biomarker is moving, heart rate variability, some other measure that is not influenced by you.

And the beauty of using biological markers is if we contrast that to performance and I said, "Okay, here's our performance test. Every day you come in, you're going to do a vertical jump, and if one day you come in, all of a sudden your vertical jump is super low, I might think, 'Oh man, maybe we're starting to overreach.'"

You also could be feeling lazy that day and just not have jumped very high on purpose because you didn't want to work out. The beauty of biomarkers is you don't get to manipulate them like that; they don't care.

There's a downside to it, which is maybe they're just indirect markers, right? And so I'm not telling you biological markers are better than performance markers. What I'm saying is you want to look at both.

All right, in fact, you want to look at our third category as well, which is some sort of symptomology. And so am I having a symptom of overreaching? Am I seeing a performance decrement? And then am I seeing a biological marker as well?

If you see all three of these popping up, you have reason to believe you've reached some overreaching. Now, what you have not identified yet is if that is functional overreaching, non-functional overreaching, or true overt training.

And remember, you shouldn't be feeling great after every training session. You're trying to cause adaptation, and until you back off, maybe even weeks or months later, to actualize the adaptation and get that super compensation and performance increase, you're going to have to invest a little bit.

So you're going to go in the hole. Any sport performance coach is going to look at numbers throughout the year and say, "Yeah, yeah, when we first start training and preparation for this season, we are going to see a drop in performance that day, that week." That's part of the plan, though, right? That's the stress you're trying to accumulate.

So you want to see all three of those markers. You just want to pay attention to a couple of things: how long are they down for? A day? Three days? Seven days? Fifteen days? Etc.

If you're seeing a performance drop in a day and I am far away from performance, so the day that I want to peak for, I'm not going to do anything different. If I see two days in a row drop performance, I'm not worried. If I see more than probably, in my opinion, five days in a row of decrement, then I might start paying attention.

If you're in season, though, or close to competition or whatever that thing means to you, and you see more than a couple of days in a row of dropping, then you might actually want to take some steps to mitigate that.

So it really is important you understand again what are we trying to do? Are we trying to cause adaptation? Are we trying to cause adaptation? And I have a very specific example of all this we can run through here in a second, and then of course a bunch of tools to pull you out of those phases.

But that's fundamentally what we're trying to do here. I would encourage you again, don't be too reactive and responsive to any one measure. I'm going to cover a whole bunch of them in a second, but you can get lost in different things because they all have pros and cons.

And so I know it's simple to just look at one score on your watch and make your decisions because of that or check your app, but you really want to be careful of doing that. You're going to probably lead yourself in the wrong direction more often than you're going to help yourself.

I'm curious as to why when we overreach too much or too often or we are overtraining, that performance is diminished. Because on the face of it, it's kind of obvious. You're overreaching, you're overtraining, so performance has diminished. But that's completely circular.

You hear about things like adrenal fatigue and adrenal burnout. Well, it turns out adrenal burnout doesn't even really exist. Absolutely not. There is such a thing as adrenal insufficiency syndrome, but of course, you know, these phrases like burnout, adrenal burnout, overtraining, they're thrown around, you know, as much as words like gaslighting and obsessive-compulsive, you know, are without any real clinical definition.

Or there are clinical definitions, but people aren't obeying them when they use the language. I do want to acknowledge, however, what is absolutely true, which is that overreaching too much, too often, overtraining, these can degrade performance.

But mechanistically speaking, what's going on? Because I think once we understand what's going on mechanistically, then I think we can all look at tools, whether or not it's breathing, movement, compression, thermal, psychological, motivational, etc., and have a much clearer sense as to what's going to work best and what likely won't work.

I love this question so much because, as I mentioned at the beginning, I was fortunate to spend some of my graduate work in Andy Fry's lab at the University of Memphis, and we did a lot in this area.

In fact, this is how I learned how to do assays and run Western blots and measure signaling proteins and things like this, so this stuff is near and dear to my heart. We also did a bunch of really wild studies, and he had done some before I got there.

So I'm going to combine kind of Andy's entire career and just highlight some of the big pictures of what he found there. He was very interested in exercise, particularly strength training, and trying to figure out this entire question, right? Which is like, why is this actually happening? When I work out too much, when I lift too much, that all of a sudden I can't sleep? What's happening?

Like, why is my energy down? Why is my mood, my motivation reduced if I squat too much? So we did a whole series of studies across his career, and again, I'll just sort of highlight some of the themes that ran through them.

So the first one that jumps out to mind is early in his career, he did this really awesome protocol where he had people squat 100% of their back squat max every day for two weeks. So you come into the gym, and I think this first one was on a machine, and you did a one-rep max, and then you came back in every single day for two weeks.

So these are what we would generally call kind of like that short to moderate range overreaching, and by definition, some of them ended up actually being true overtraining because it would take the individuals sometimes two to up to eight weeks to return back to their one-rep max at the end of these protocols.

So some of them were non-functional overreaching or some combination of that. Well, along with that, he took a lot of blood samples as well as muscle biopsies to try to look at what's happening endocrinologically, neurologically, muscle physiology-wise to pay attention to what's happening.

So a couple of things that jump out there. One of his initial studies, actually I think the very first one he did, when they ran that first squat everyday protocol, what they found was catecholamine levels changed quite significantly.

And depending on kind of what you wanted to pay attention to there, whether it was epinephrine or norepinephrine or even some other markers, they basically increased by somewhere between two to three-fold.

And so a little bit of understanding of sleep physiology, if adrenaline is extremely high, epinephrine, you're going to have a hard time sleeping. So that alone was the first indication this is like, "Wait a minute, something's actually happening here that's just beyond muscle soreness."

There's some sort of systemic fatigue happening, and as you rightfully pointed out, it's not the adrenal glands becoming fatigued. That's sort of a bit of tongue-in-cheek and pedantics. It is cortisol dysregulation and general stress syndrome.

But it can really be noted in blood in terms of epinephrine and norepinephrine. Another study he had done of a similar realm was over the course of seven and a half days. People came in and did 15 training sessions, so it was really cool.

These are these really short bouts of just ridiculous training, and they said, "Okay, like something's happening with epinephrine and norepinephrine, something HPA, something's happening with testosterone."

What's it look like inside the cell? So now muscle biopsies came on board, and they started looking at things like MAP kinases, which are these signaling proteins that are tend to be associated with an anabolic response. They upregulate muscle protein synthesis and do many other things, but that's like a big factor of them.

They looked at various androgens and glucocorticoid receptors, and they wanted to see, "Well, maybe receptor density or androgen sensitivity is changing." And in fact, surprise, surprise, that's exactly what they found.

So they found both androgen and glucocortico receptor concentrations were reduced, and so you can start to see a picture forming, which is like, "Hmm, very similar to the insulin type 2 diabetes story where you've really put yourself in a very high-stress situation."

So presumably, epinephrine, etc., testosterone releases are extremely high in response to that to try to reach back to some level of homeostasis. You start downregulating the receptors for them, and so it's like the signal can only get so high. If you're going to keep that gas on, we're going to pull back the throttle and the receptors so that the total signal stays the same, if that makes a little bit of sense.

Well, that becomes obviously problematic. So then, like a final follow-up study here that is important to note is they did another protocol, which was really, really cool, and they said, "The first ones weren't enough, so how about this? We're going to come in every day for two weeks, and we're going to do 10 sets of a one-rep max every day."

So they were coming in, and they would do 10 one-rep maxes every day for two weeks. And what's really cool about that study, if they didn't complete any of the repetitions, they had to repeat it until they had 10 successful one-rep maxes on that given day.

Absolutely brutal protocol. I wasn't there at the time. They had finished that right before I got on campus, but I was actually able to be around when they were doing some of the final analyses there of the tissue.

What they wanted to look at in this particular study was beta-adrenergic receptors, which are those receptors where epinephrine and such are going to be binding for. So again, similar story here.

Perhaps are we losing overall sensitivity because of this extreme sympathetic stimulation? Now, actually thinking back, what would have been pretty cool is if they had another group that did it and then did some down-regulation breathing post to see if that can mitigate some of the problems.

But of course, this was 20-plus years ago or something like that. So a couple of things that happened is the one-rep maxes dropped by I think around like 8 kilos by the end of the two weeks. If I remember right, like the group average was something in the neighborhood of 151 kilos.

So these were pretty well-trained individuals, and it went from, rather, I think actually it was about 160 kilos, and they dropped to like 152 kilos, something close to that. What was more significant, though, was their power dropped by 35%, which is really, really interesting.

Because if you pay attention to declines in physical performance over time, and I mean that like through aging, what you'll see is people can hold on to muscle mass pretty well. It will go down by about, you know, 1% or so after the age of 40.

However, strength will go down at like 2 to 4%, and then power by 8 to 10%. And if you look at actually world records across strength sports by age, you'll see that they will decline by age, but not that much.

However, if you look at speed sports by age, they fall off the planet. So it's very challenging to preserve speed through time, whether this is fatigue or because of age. That's really important because that'll then tell you, "Hey, a little bit of a canary in the coal mine is not necessarily your strength but your speed."

And so a lot of different techniques that we use to measure performance, remember that's our triad, right? Symptomology, physiology, and performance. You're generally better looking at speed-based performance tests rather than strength-based performance tests to get an earlier indication of potential overreaching or overtraining.

So anyways, back to the individual study there. In that same group, again, we had the same problem where it took some of them 2 to 8 weeks to come back. So what they had to do is, I can't remember the exact time frame. I probably should have thought through this, but they had to come back something like every week or every couple of days even after the study finished until they got back to their baseline one-rep max.

And some of them, it took them up to eight weeks before they finally got back. So they probably were in a classic overtraining state at that point, which was done in as little as two weeks.

And this is also another point that people always ask: "How long does it take? Is this something that has to happen over the course of months? Or if I were to go do two-a-days or this intense training camp for two or three weeks, could I actually cause overtraining?"

And the answer is if it is actually truly enough volume and enough intensity, you probably can do some significant damage in as little as two weeks.

It probably doesn't happen that often. Most likely, you're probably going to be reaching a state of non-functional overreaching, but you may actually be able to put yourself in a position where it might take three or four weeks or more to get back to baseline after a truly intense—and again, think about this protocol—it's like totally unrealistic for the most part.

10 sets of a one-rep max squat every day for two straight weeks. Some folks, if you're an extremely highly trained weightlifter, you might do something like that when you're very close to, say, world championships. But outside of that really specific scenario, it's a totally absurd training protocol.

But that was the point, right? We were trying to ensure that overtraining was met or close. It's similar to when we've done, we've actually done, I think, three studies in the Center for Sport Performance on DOMS, muscle soreness, and in all those cases, you do just like ridiculous leg extension protocols because you're just trying to ensure you cause super soreness.

If you don't, then you have nothing to study. So absurd training protocols, but that's the point. So nonetheless, as a result, sure enough, the beta-adrenergic receptors were regulated by something like 37%.

What's probably even more significant, though, was the sensitivity in those receptors was reduced by like two and a half-fold. And so it's like, "Okay, wait a minute, we're becoming desensitized to this time."

And we're also actually now starting to reduce our total concentration, similar, which is actually an interesting, was a very sneaky smart thing to do, is they looked at nocturnal urinary epinephrine, and guess what? That was also up by like 50%.

So now you're seeing this tie-in where it's like I'm seeing response at the tissue level, I'm seeing a response probably, although they didn't actually look at a pituitary or anything like that, I'm seeing adrenal and other endocrinological problems, and then I'm also seeing this increase in concentration of epinephrine when I'm supposed to be sleeping.

And surprise, surprise, I'm having a hard time sleeping.

**Symptomology**

Well, that's a very interesting finding about nocturnal epinephrine. Epinephrine, of course, is adrenaline. It's released from the adrenals, no surprise there, but also from this brain area called the locus coeruleus in the brain.

And the brain tends to be called epinephrine in the body, adrenaline, just to complicate everyone's understanding. But that nclat did not come from us, so don't blame us.

The point is that rapid eye movement sleep, so-called REM sleep, is more abundant in the second half of the night. We know that the dreams associated with rapid eye movement sleep are more emotionally laden, and that those dreams and those emotional states are actually important for discarding the emotional load of previous days' experiences.

It's a sort of a natural trauma therapy, if you will, because in the normal healthy state, those dreams are associated with an inability to release epinephrine at night.

So for me, what you just described, first of all, it's the first time I've ever heard of it, but it ties together something really quite clear from the sleep neuroscience literature, which is that when people are stressed, they tend to get less rapid eye movement sleep.

That rapid eye movement sleep normally is associated with low levels of epinephrine. So whether or not it's causal or not isn't clear, but sort of doesn't matter for the sake of this discussion.

But what I'm wondering, and I suppose one could test for but maybe observe, is whether or not people who are overtraining too much, overreaching too much, because of this elevated nocturnal epinephrine, diminished REM sleep, whether or not their emotional state is also disrupted.

Because one thing we know for sure is if you want to disrupt somebody's emotional state, you deprive them of sleep, and rapid eye movement sleep in particular.

The one caveat to that is for those of you out there that have heard that rapid eye movement sleep deprivation, deliberate rapid eye movement sleep deprivation, is a treatment for depression, that is true, but it's coupled with a next night enhanced rapid eye movement sleep.

One of the major takeaways from all of this that I'm realizing is that, no surprise, daytime activities impact nighttime endocrine function, impact quality of sleep, impact daytime activities.

Yeah, actually, there's so many fun things I want to do here now. This is actually why measuring eye movement is a very fantastic tool for understanding total stress load, and you can actually differentiate different types of stress.

So caffeine use versus alcohol use versus sleep deprivation by actually measuring eye movements. That's actually what we do in our Absolute Rest Sleep Company. In addition to getting a full PSG sleep study done in your bedroom, you're going to get an eye tracking assessment, which we're going to be able to figure out why you're getting there.

So nonetheless, yeah, if you actually look at the classic signs and symptoms of overtraining or overtraining syndrome, it's going to be everything from performance decrements, like we talked about, resting heart rate is going to increase.

You're going to see things like HRV drop by generally 20% or so. That would be a very large disruption in HRV. Decreased body weight, and then all the stuff Andrew just talked about—motivation, adherence, appetite, mood—all of this stuff are classically known associations with overtraining.

And that's for the exact reasons you're talking about: sleep disturbances and disruptions, wanting to train, motivation, all of this stuff goes part and parcel with non-functional overreaching and/or overtraining.

You can actually tie this back in a little bit more to some other biomarkers, and this is great because this is the stuff we look for. This is the physiology stuff we look for.

You've probably talked about SHBG before, which is the sex hormone binding globulin. So it's this protein that floats in your body that's going to bind up sex hormones, in particular testosterone.

So what happens with overt training is you can actually take this serially, like week by week, and you will actually see this number rise. And so if you see this, like say you're using a service like InsideTracker and you're getting your blood measured every so often, and you see this number start ticking up, this is actually associated with that.

Because what's actually happening is it's binding up all your free testosterone, and that's just leading back to the circle we're talking about. And you can actually see the same thing happen with calorie restriction—just not eating enough calories.

But in this particular case, because it actually happens in both scenarios, you know it's not an issue simply of being under-caloric. It's clearly an issue of the training load being too high.

So just to give another little tool, I can get the link for it, but there's a website that was created by which journal—oh, slipping—but I'll get it to you. You can link it up where you can actually go in and plug in a number of values from blood chemistry.

So if you got your blood work done, and you can plug in your pre-number and your post-number, so say you got it done, and then maybe 10 weeks later you got it done again, and you're wondering, and you notice, "Hey, my free testosterone's down," or "My SHBG is up," is it actually a meaningful number?

And it will actually tell you whether or not the change pre-post is physiologically meaningful or not, or just within the error margin of the measure. And you can actually change, like right there on the website, you can change your confidence interval.

So it's really, really cool if you know if you just have your own blood and you want to know, like, "Hey, I had any level this year, and now it's here over there." It's just a totally free resource created, gone through peer review, all that stuff.

And I'll give the link to that, so that's a pretty cool measure. In addition to that, like probably one of the more powerful and easy metrics biologically is to take your cortisol and DHEA ratio.

So this is known to be associated with a lot of things. You want to be really careful; you don't want this number to be too high or too low. Something like 0.09 is about cortisol to DHEA.