Dr. Andy Galpin: Optimal Protocols to Build Strength & Grow Muscles | Huberman Lab Guest Series

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 marks the second episode in the six episode series with Dr. Andy Galpin, a professor of kinesiology at Cal State University, Fullerton and one of the foremost world's experts on the science and applications of of methods to increase strength, hypertrophy and endurance. Today's episode is all about how to increase strength, speed and hypertrophy of muscles. Professor Dr. Andy Galpin. Great to be back. Last episode you told us about the nine specific adaptations that exercise can induce. Everything from strength and hypertrophy to endurance, muscular endurance, so on and so forth. And you gave us this incredible toolkit of fit tests for each of those adaptations so that people can assess them for themselves and then of course improve on each and every one of them if they choose. By the way, people can access that information simply by going to the first episode in this series with you and it's all there and timestamped and I highly recommend people do that. Today we're talking about strength and hypertrophy. And so right out the gate I just want to ask you, why should people think about and train for strength and hypertrophy? And that question is of course directed towards those that are trying to get stronger and grow bigger muscles. But I know that many people out there perhaps have not thought about the benefits of strength and hypertrophy training and how beneficial it can be not just for people that want to get bigger biceps, et cetera, but that have other goals, longevity goals and health goals unrelated to what most people associated with hypertrophy. So what are the benefits of training for strength and hypertrophy for the everyday person, for the athlete, for the recreational exerciser and so on?

There's a wonderful saying. I think it was Bill Bowerman, the founder, one of the founders of Nike, and he always said, if you have a body, you're an athlete. And I think that's very important for people to understand because one of the major disservices we've done in this field is convince people that things like strength training are for athletes or for growing bigger muscles and cardiovascular training are for things like fat loss and heart health. And that is a tremendous disservice because it puts a lot of unnecessary barriers and leads to a lot of false assumptions and therefore poor actions. Classic examples of this are people who are resistant to strength training because they don't want to put on too much muscle. People who only perform one type of exercise because they want, say, fat loss or they're in it for longevity and health, and they don't worry. They're not worried about being an athlete. And so right out the gates, we can actually draw back a little bit to what we were. Our previous conversation when I walked you through the history of exercise science. And the reason I did that is to help you understand these are the railroads that you're running down and you don't even realize it in terms of everyone thinks of strength training and they immediately default to our principles to optimize muscle growth. And that's not the only adaptation one should be after with strength training. When we think of endurance training, we immediately default to things like, again, cardiovascular health or fat loss or things like that. What I really want to do across this entire series and conversations is to just break that immediately. Talk about all the other things that you can do with your training and so that people can be comfortable and confident and doing an optimal training program for whatever goal they have, whether that be specific, like growing muscle, or non specific, like just feeling better, having more energy, being more prepared for life and longevity. And so to directly answer your question, I could really, we could do a hundred episodes on the benefits of exercise, and we could run all the way from mood and focus cognitive tasks to a better immune function. You'll get less colds, you'll be. You'll fight them off more effectively to mortality. Right? So some of the strongest predictors of how long and how well you will live are exercise. However, there are independent benefits that come from just endurance training, and there are independent benefits that come from strength training. And so to just give you one categorically, the way that you want to think about this is resistance exercise. And strength training is the number one tool to combat neuromuscular aging. You cannot get that through any other form of exercise besides heavy overload strength training. And we can walk through in detail what that is, but that is reason, number one. In general, human movement is a function of, number one, some sort of neuromuscular activation. So nerves have to turn on. The second part is muscles have to contract. And the third part is those muscles have to move a bone. All right? If you want to be alive and you want to live by yourself, you have to be able to engage in human movement. If you have any dysfunction in the neuromuscular system there, then you're not going to be able to do that. And again, as I mentioned the only way to preserve that or fight that loss of aging is to strength train. So people will tend to hear numbers like, you lose about 1% of muscle size per year after age about 40. And that's true. However, what they don't realize is you lose about 2 to 4% of your strength per year. So the loss of strength is almost double that. The loss of muscle mass with aging, muscle power is more like 8 to 10% per year. And so we can very clearly see the problem you're going to have with aging is not going to be preservation of muscle, although that is incredibly important. It's going to be very specifically preservation of muscle power and strength. And why that really matters is your ability to, again, stand up and move, your ability to catch yourself from a fall, your ability to feel confident doing a movement that is a function of muscle power more than it is muscle size. And so functionality is really what we want to be. Right? You want to be able to do whatever you want to do physically and feel confident in doing that as you age. That's going to only be obtained through strength training.

So is it appropriate to say that training for strength and hypertrophy is also a way to keep your nervous system healthy and young?

Absolutely. It is the only exercise route we have for that. If you look at just basic numbers like motor units, you're going to see that older individuals have like a 30 to 40% reduction in total motor units.

So when you say older, approximately what ages are you referring to? Because I know many people out there, such as myself, are 40 and older, but I know many of our listeners are in their 20s, maybe even in their teens. And I can imagine that people that start doing strength and hypertrophy training younger will afford themselves an advantage over time, but that everybody should be doing strength and hypertrophy training for as much of their lifespan as possible. That's really the message that I'm getting. So if somebody is, for instance, 45, would that fall into the bin of older?

You're going to start seeing decrements past again around the age of 40 or so now. There's a lot of genetic variation there, and a lot of other things go into that equation, like your sleep and your nutrition. But that's a fair number to sort of think about. One actually response is it's actually sort of counterintuitive. The wonderful thing about strength training is you don't actually have to start at a young age. You can actually. In fact, I was reading a paper this morning because of our previous conversation it was in over age 90. So these are folks, 90 plus, and they saw improvements like 30 to 170% in things like muscle size and hypertrophy over a very short period of time. I think it was 12 weeks. So you don't actually have to start. There are some adaptations that you're going to need for health that you. You really need to start in your 20s. The reason I like to mention that is because if you are listening and you are 50 and you're like, oh, I haven't been strength training, you're not toast. Like, you should absolutely start now, but you're going to be able to get to a fantastic spot very quickly. Similarly, though, if you are 20 or 25 and 30 and you aren't lifting, there are still many reasons why you should do that now. And I'd like to point that out because a lot of folks would be like, oh my gosh, they said I have to do it when I'm 20 or 25 or I'll be sort of screwed. And that's not the case at all. There's really no age limit on this. In fact, there's actually interesting data that just came out showing this reduction in muscle strength and hypertrophy that I sort of talked about is basically ameliorated with a preservation of activity. In other words, you don't lose these functionalities because of aging. You lose these because of a loss of training. To state that again, you don't lose these because of some innate physiological thing that happens with genes become less sensitive or you lose functionality. You pretty much can describe the loss of function of strength and muscle in aging as exclusively because of a loss of training and nutrition and anabolic resistance and some other things. So you can do a lot more than you think when it comes to maintaining high quality muscle. And that's really important to point out.

I'm reminded of the words of the great Sherrington. He won the Nobel Prize, he's a physiologist. I guess the neuroscientists try and claim him as a neuroscientist because he worked on the nervous system. The physiologists claim, as a physiologist, he.

Is 100% a physiologist.

I would call him a neuroscientist. Maybe we can argue about this later.

We will.

But I think one of the key things that Sherrington pointed out was that, and I believe the quote was that movement is the final common path. And what he was referring to was the fact that a significant fraction of the brain itself is devoted to our ability to move and our ability to engage in resistance type movements. And that resistance type movements and the continuation of movement throughout the lifespan is what keeps the brain young and healthy and vital. And there are so much data now to support that. But I'm so grateful that you brought up early this fact that there's a neuromuscular link, because I think a lot of people think about musculoskeletal, they forget that the nervous system is really in charge of the strength of the muscle contractions and the types of muscle contractions that occur. I'm certain we're going to get into that in a lot of depth today.

You're close there. Not totally right, but we're close.

Okay, well, I look forward to being corrected and to achieving the precision that you're known for around that discussion. So if we are to step back and say strength training and hypertrophy training is critical for people of all ages for developing and maintaining the neuromuscular system and for our ability to function in the world, not just offset injury, but the ability to pick things up and move, et cetera, what are some of the other things that strength and hypertrophy training can provide? I know a lot of people use strength and hypertrophy training for changing their aesthetics. What is your sense about its potency for changing aesthetics as compared to, say, cardiovascular exercise?

Yeah, the mantra I always like is the reason you want to exercise is threefold, right? You want to look good, feel good, play good. That's really. That comes from sport, comes from football specifically. We always say that. And what that means really is you want to look good, people want to look the way they want to look, whatever that means to them. And there are any versions of what you feel to be aesthetically pleasing, and that's totally irrelevant, but people want to look the way they want to look. Number two, you want to be able to feel good. What's that mean? You want to be injury free, you want to have energy throughout the day, you want to be able to execute anything you want to. So whether you want to go surf in the morning, you want to play racquetball, or you want to hike, or you want to do all three of those in one day, you should have the ability to do that. And then you want to play good, which means you should be able to execute any activities that you want to execute, whatever that means. All right, so backing all up, what's that got to do with your question? One of the major benefits of strength training is the responses tend to happen extremely fast. So you can see noticeable changes in muscle size. Certainly within a month. Absolutely, within six weeks. And so we have this wonderful feedback loop that sort of tells you, am I doing this thing correctly? Oh my gosh, yes, I am. Also, it's very addicting, the feedback, the response, the physical changes. Whether this is actually point two or three, look good or feel good, play good, or it's even just part one. You're starting to see that when you compare that to things like fat loss, that journey tends to be longer, it's more difficult, it's more reliant upon other factors like nutrition, et cetera. Strength training is really about like, there's some very minimal nutrition requirements outside of that. It comes down to the training and the feedback is immediate. That's powerful because if you look across the literature on exercise adherence, you'll see that that is in fact the number one predictor of effectiveness of any training program. So what that means is if you were to put any variable possible and figure out what is going to determine whether or not this program works. This is what we typically call the methods are many and the concepts are few. So the methods of exercise, the methods of strength training, the methods of hypertrophy training, which we'll talk about, are infinite. However, there are only a handful of key concepts that you have to achieve in order for that program to work. Adherence is one of them and again is often the top one. So you need to do something, you need to do something consistently. When you are getting that feedback and you're seeing results in your appearance immediately, and you see that every single day, every time you take off your shirt or every time you look in the mirror, you see that result. That tends to drive adherence really powerfully. So it's important to give people wins, especially people who are not maybe like you and I, who are like, I'm going to lift weights and I'm going to exercise like no matter what the rest of my life, because I just love it. Not everyone's like that. And so giving them a little bit of carrot of success. And if you can achieve that in, you know, say three to four to five weeks already, it's very powerful tool.

Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is also separate from Dr. Galpin's teaching and research roles at Cal State Fullerton. It is, however, part of our desire and effort to bring zero cost to consumer information about science and science related tools to the general public. In keeping with that theme, we'd like to thank the sponsors of today's podcast. Our first sponsor is Momentous. Momentous makes supplements of the absolute highest quality. The Huberman Lab Podcast is proud to be partnering with Momentous for several important reasons. First of all, as I mentioned, their supplements are of extremely high quality. Second of all, their supplements are generally in single ingredient formulations. If you're going to develop a supplementation protocol, you're going to want to focus mainly on using single ingredient formulations. With single ingredient formulations, you can devise the most logical and effective and cost effective supplementation regimen for your goals. In addition, Momentous supplements ship internationally and this is of course important because we realize that many of the Huberman Lab podcasts listeners reside outside the United States. If you'd like to try the various supplements mentioned on the Huberman Lab podcast, in particular supplements for hormone health for sleep optimization for focus, as well as a number of other things including exercise recovery, you can go to livemomentous spelled o u s so that's livemomentous.com huberman Today's episode is also brought to us by Eight Sleep Eight Sleep makes smart mattress covers with cooling, heating and sleep tracking capacity I've been using an eight sleep mattress cover for for about the last eight months and it has completely transformed my sleep. I'm sleeping about the same amount, but I'm sleeping far deeper and I'm now getting the proper ratios of so called rapid eye movement or REM sleep and slow wave sleep and waking up feeling far more recovered mentally and physically. The underlying mechanism for all that is very straightforward. I've talked many times before on this podcast and elsewhere about the critical relationship between sleep and body temperature. That is, in order to fall asleep at night your body needs to drop by about 1 to 3 degrees in terms of core body temperature and waking up involves a 1 to 3 degree increase in core body temperature. With eight sleep mattress covers, you can adjust the temperature of your sleeping environment to be one temperature at the start of the night, a different temperature the middle of the night, and a different temperature as you approach morning, each of which can place you into the optimal stages of sleep and have you waking up feeling more refreshed than ever. If you'd like to try Eight Sleep, you can go to eightsleep.com huberman and check out their Pod 3 cover and save $150 at checkout. Eight Sleep currently ships in the USA, Canada, United Kingdom, select countries in the EU and Australia. Again, that's eightsleep.com huberMAN to save $150 at checkout. Today's episode is also brought to us by levels. Levels is a program that lets you see how different foods and activities affect your health by giving you real time feedback on your blood glucose using a continuous glucose monitor. Many people are aware that their blood sugar, that is their blood glucose level, is critical for everything from fat loss to muscle gain to healthy cognition and indeed, aging of the brain and body. Most people do not know, however, how different foods and different activities, including exercise or different temperature environments, impact their blood glucose levels. And yet blood glucose is exquisitely sensitive to all of those things. I first started using Levels about a year ago as a way to understand how different foods, exercise, and timing of food relative to exercise and quality of sleep at night impact my blood glucose levels. And I've learned a tremendous amount from using levels. It's taught me when best to eat, what best to eat, when best to exercise, how best to exercise, and how to modulate my entire schedule from work to exercise, and even my sleep. So if you're interested in learning more about Levels and trying a continuous glucose monitor yourself, go to Levels. Link Huberman. That's Levels. Link Huberman. Let's talk about strength and hypertrophy. If you would, please remind us what strength and hypertrophy are in terms of the specific adaptation they represent. What I mean by that is, when somebody is training for strength, what are they really training for? Obviously, it means the ability to move more weight, but I know that it includes a number of other things as well. And when one is training for hypertrophy, for the growth of muscle fibers, what does that represent? Because I think if people understand that, they will far better understand the methods and protocols that are going to be best for strength and hypertrophy at its core.

You've basically described it. When we talk about strength, we're talking about an actual function. So can you create more force across a muscle or muscle groups or total movement? And when we talk about hypertrophy now, we're specifically referring to just an increase in size. There's no actual mention of function. So a muscle can grow larger without actually technically being stronger. For a number of reasons, however, there is a strong relationship between strength and hypertrophy. So a lot of the times in the general public, in the lay conversations, we sort of lump those two things in as the same thing. And so we have to recognize people who are new to training or people even are intermediately trained. There is a huge overlap between strength and hypertrophy. Once you get past that, though, they become disentangled. And a good example of it is this. If you look at the strongest people in the world, this would be people who compete in the sport of powerlifting, right? That's a true test of maximal strength. So it is a deadlift, a bench press and a back squat. And you're going to do a one repetition max in all three of those. And so whoever wins is the person who lifted the most amount of weight one time. That's it. It's not like World's Strongest man where it is, how many reps can you do in a row or your time, right? It's a true maximal strength test. And you compare those to, say, bodybuilders. Now, both of those individuals are strong and both of those individuals have a lot of muscle. However, it is extremely clear the power lifters will be significantly stronger than the bodybuilders on average, right? There individual exceptions, but we're just talking collective averages. And the bodybuilders will have more muscle than the other ones. In addition, whether you look at Olympic weightlifting or powerlifting or World's Strongest man for that matter, there are weight classes. And the reason is as you go up in weight classes, you will always see the world records go higher and higher and higher, right? So you can clearly get stronger without adding any muscle. However, there's a point, right, where you simply have to add more mass to get a higher number. And that's why we have weight classes in those sports and in combat sports and lots of other things. So we have. There's a lot of confusion, right, because people think, man, either these are the same thing, or if I want to get stronger, I have to get bigger, which is not the case at all. Another misnomer here is I can't get stronger unless I add muscle. That's not true either, right? It's a similar idea. So what I'm saying is you have the ability to do whatever you'd like. If you'd like to get stronger and add muscle, great. If you add muscle, you're probably going to bring some strength along for the ride. However, if you want to get stronger and you don't want to add muscle for any reason, personal preference on aesthetics, whether you're in a weight class and you simply can't afford it, it is quite easy to get stronger and not add much muscle mass either. And so differentiating these two things is one of them is simply a measure of size and the other one is a measure of force. And when we talk about strength, what we're really talking about are two unique components. Component one is what I call the physiology. So what is the ability of the neuromuscular system? What is the ability of the muscle fibers to contract and produce force? The other one is what we call mechanics. And mechanics is simply things like it's minutia down to how long your femurs are relative to your tibia, or other things like, this is biomechanics. This is also technique. This is skill. This is how smooth do you feel? This is. Are you firing the right muscle group in the right sequence and order? And all of these things play into strength. So somebody who maybe has more force capability in their muscle fibers, but their technique and the movement is worse, may lose in a competition or somebody, again, who's like. If you go into the world of speed and power especially, you'll hear a lot of people talk about, like, the rhythm. And there's just a certain rhythm that has to happen if you want to jump as high as possible or run as fast as possible. But that's all mechanics at this fundamental level. So when we look at hypertrophy, it's just still simply about how big the muscle is. So those are really the similarities and distinctions between strength and hypertrophy.

When strength improves and when hypertrophy increases, is there also involvement in the ligaments and tendons? That is, of course, the ligaments and tendons are involved in the movements. But do ligaments and tendons themselves be. Grow and. Or get stronger?

This field is really difficult because connective tissue is not vascular. And so their plasticity is significantly lower than skeletal muscle. In fact, if you look across all the organs, skeletal muscle is one of, if not the most plastic, meaning it's the most pliable, the most responsive, the one that's going to adjust. It's basically, it's paying attention to everything that's being said in the body. You cannot change blood pressure or ph or macronutrients floating around without muscle knowing about it. It is, in fact, this is why we call muscle an organ. People don't tend to think about this. If you were ever on, like, Jeopardy. And they ask you that question of, like, what's the biggest organ system in the body? People tend to say the skin muscle is actually the correct answer.

All right, well, I'm going to cite you. When I get it.

You'll probably get it wrong. At Jeopardy.

On Jeopardy. I don't have any immediate plans to go on Jeopardy. But who knows?

Oh, there you go. Celebrity Jeopardy. Had you Huberman wait.

I Don't know about the celebrity part, but Jeopardy. Would be fun. But I will say the muscle. And if you get a phone call on Jeopardy. I don't know. I haven't seen that show in a very long time, maybe ever. Then I'll call you. But that makes sense. Muscles would be the largest organ system in the body.

The reason I was saying that is. So muscle is both listening and talking. It is controlling the immune system a lot. It's controlling blood glucose regulation. It is the central depot for amino acids which are needed to do things like regulate the immune system, build any new red blood cells. A lot of this stuff is coming from skeletal muscles. So when we say organ, by the way, that's actually like a physiological definition. So something that's communicating to either another organ itself or throughout the system. So it's listening and it's talking. Connective tissue is not the same way. And so we do see adaptations with strength training in connective tissue, it's just much lower. It's difficult to measure effectively. What we know now is you're going to have a combination of adaptations throughout the connective tissue. It is beneficial. This is probably one of the major reasons that's that strength training reduces injury risk, which is very, very important, because people who tend to want to pick up an exercise routine after, say, 10 years, the classic cliche is like, I played all these things in high school, then I went to college, got a job. Now I'm 25 or 35 or whatever. And you sort of want to jump back into what you did when you were 20. Well, there's no tissue tolerance left. And what we almost always mean by that is connective tissue. The tolerance in there is not ready for the load you're about to handle. And so you go through some movement and then boom, sprains, tears, you know, even like, the more significant ones are on Achilles tear, which is going to really sideline you. So those are some of the problems. And we know strength training has a large role in injury reduction for stress and strain and overuse injuries. And that's specifically coming for the connective tissue adaptations. Again, the difficult part here is it's very hard to assess. We actually, when I was a doctoral student, we played around with patella tendon biopsies. So I actually had one. This is like a.

There's a little piece of your patella tendon missing.

Yeah.

Because your own lab.

So now I've probably had, I don't know how many hundreds of biopsies I've performed on people. Probably well over a thousand. Certainly well over a thousand. I've probably had 35 or 40 done on myself. There's no problem here. I have no scar tissue. I have no loss of function. And I've stuck needles in every leg, like all over myself. Right quads, my soleus gastroc, like all up.

Taking tissue out.

Yeah, you want the needle? Looks like a pen, basically. And you, you know you're alive and you go in and grab a chunk and you pull it out and can.

I come to your lab and get biopsy?

Absolutely, yeah.

You're probably looking under the microscope. It'll just look like the molecule caffeine.

There's a. There's a mutual friend of ours who came down and did that. He's a big, big, big gentleman. Big into lifting, very into strength training. And he went to that experience and he was like, oh, my gosh. It was not what he was hoping to get. He actually had unbelievable muscle morphology. His fibers were. The diameter of muscle fibers is extremely large. It's one of the biggest cells by volume in all of biology. Skeletal muscle in human.

How large? Can't help myself. Millimeters.

Well, you. So you have length and then you have width. Right. So lengthwise they can be extraordinarily long. You can be. The classic example is like your sartorius, which is like the front of your hip to the inside of your kneecap. Theoretically, those cells can run the entire length, which would be one muscle fiber running that thing. If I were to do a biopsy on you and I pulled that tissue out, I could actually pull an individual fiber out with tweezers and hold it up and you could see that whole muscle cell.

Yeah, I'm definitely not coming.

You'd be stunned how big they are. Anyways, his was the size of a rhino. So the diameter of his. Now he has a well documented assistance in the area of muscle growth. We'll say. But yeah, those can be large. So what were we even talking about there?

Well, I was asking about tendons and ligaments because I'd like to understand the various tissues and organ systems that adapt when one gets stronger, when muscle tissue grows. And I do want to ask about bone, and here I'm not referring to bone mineral density. What I was going to ask is whether or not bone itself can grow and get stronger. And the reason I'm asking is there's a favorite result of mine. I have about 3,800 favorite results, 3,000 pet peeves and 3,800 plus favorite results.

And.

But one of my favorite Results is from Eric Kandel's lab at Columbia. Eric won the Nobel Prize for learning and memory. And his laboratory got really into the effects of exercise on learning and memory. And they had this incredible result, which is that load bearing exercise stimulates the bones to release something called osteocalcin. Excuse me. And then osteocalcin acts as a more or less a hormone, travels to the brain and enhances the memory systems in the brain by enhancing neuron health. That's the basic crux of the studies. There were several of these. And the moment I saw the first of those studies, I thought, well, here's another reason to do resistance type exercise and not just aerobic exercise. And then it brings to mind whether or not bones themselves get stronger when we do resistance training. I don't know the answer to that.

Yeah, that's very clearly demonstrated and we've known that for many decades. You have a diminishing ability to do so with age particularly. You need to do this in your teens and twenties. This is where you're going to have the largest ability to enhance bone mineral density. And it's particularly responsive to axial loading. Now, I'm a muscle guy, I'm not a bone specialist, so we would have to consult somebody who can give you more precision here. But that's.

Can you explain axial loading?

It's up and down, it's vertical.

Okay. So it's almost like a cylinder weight on the small end of the cylinder, on both small end of the cylinders. If someone doesn't do this in their 20s or teens, however, can we assume that some degree of positive change will occur if they do resistance training? Even if it's a small fraction?

The answer is yes, it is small. We have worked with a number of women in our rapid health program that come in and they are in their 20s and they're in their 30s and they have significant bone marrow density problems. And eight months later, we can see noticeable changes that are outside of the measurement error of a dexa.

Positive change.

Positive changes. Correct. And if you worked with, there are many physicians that specialize in this area, you're going to need nutrition here. Strength training alone is probably not going to get you there, particularly with women, because you have to figure out why. And there's a lot going on with the physiology and biochemistry. So you probably like almost surely needed to have some blood chemistry done with that. You have to figure out what's going on menstrual cycle wise. In fact, like oftentimes what we'll do for our women very Specifically is we use a thing called the rhythm plus a 30 day test. So you can actually do a salivary test across the entire menstrual cycle and you can take samples, it's about every other day. So you'll get 15 or 16 samples and you get a really beautiful picture of what's happening hormonally across the entire menstrual cycle. And that's really, really important because typically for women, if you get a single sample or simple time point, whether it's salivary, urine or blood, you can have well like order of magnitude difference in any number of metrics because of what phase are in. This is one of the many reasons why it's been such a challenge to do a lot of physiology research with females. Some metrics change throughout the menstrual cycle, others don't. Like strength is a very good example. I can strength train and I can do a one rep max test on a woman at any point. I don't have to do that at a certain phase of their menstrual cycle because the evidence I think is pretty clear at this point that number won't change. So I have no qualms. Including females in any of my studies where strength is an absolute is an important dependent variable. Because I don't have to adjust around menstrual cycle. Other factors like anything in blood, anything hormone related, you're going to have to automatically account for it. So what I would say is those folks should absolutely work with a qualified physician and you're going to have to get some nutrition supplementation potentially and then maybe even some other stuff going on to make that even more complicated. If you're on any form of birth control or not, that's going to change the entire equation, especially if it's a hormone based birth control. So it just gets really, really complicated. To answer it though you can see adaptations, they are significantly diminished relative to if you have started in your teens and twenties. But there is hope. You just need to work with somebody who specializes in that area.

So for both men and women, boys and girls, what are the major adaptations that occur to underlie improvements in strength? And if you would, if you could just provide a bullet point list of that and then we can dive into each of those in detail. For instance, are nerves getting more efficient at firing? Are bones enjoying adaptations in different bone connective tissue relationships that underlie strength? I have to imagine all of these things are happening, but what are the major changes that are occurring in those organs and organ systems that reflect someone's ability to on one day lift 100 pounds and then a week later to lift 105 pounds.

Now, I'll try to keep this condensed again. This could be an entire university course. I will also try to give you a little bit of bones here. So normally, as a muscle guy, I take all the credit in muscle. Turns out the nervous system gets a little bit of credit too, here.

Thank you.

So as we walk through it, just as a big picture, if we think about, again, what causes human movement, basically everything along that chain will improve the strength training. And I'm not really being using too much hyperbole there. It's quite impressive. So just going from the nervous system side of the equation, what has to happen for human movement is a nerve has to send a signal through a motor unit. Now, motor unit is. Comes down and innervates multiple muscle fibers. So if you think about your actual muscle, it's not a thing. It is a component of many individual muscle fibers. So you've got millions, if not more. Think of it like a ponytail. So we collectively say ponytail and you think of it as like one thing, but really a ponytail is a combination of tons of individual hairs. Okay. Muscle is the same way. So this motor unit comes in and innervates a lot of different muscle fibers. Now, every one of the fibers in a motor unit is generally of the same fiber type. So fast twitch or slow twitch, and they are not laid out next to each other in the muscle. They are spread out across horizontally, vertically, as well as closer to the bone and further to the surface. So they're moved throughout the entire way. And this is what allows you to have smoother contractions and you don't have spasticity and things like that. So we see improvements from the neuromuscular side, like firing rate, we see synchronization improvements that are coming in. You also see improvements in things like acetylcholine release from the presynaptic neuron. So you're getting it faster. We see calcium recycling is improved back to there. So, you know, in order for. Without walking into too much of the biochemistry, in order for a signal to go from nerve to muscle, there's a little bit of a gap. There's a physical space that happens. And what happens is you release this molecule called acetylcholine. This goes into the postsynaptic cleft, and then that actually binds to a receptor. That receptor actually opens up a door that lets sodium in. That's really what's happening. So it's not acetylcholine. Well, that acetylcholine then sits on that receptor site, it's broken down, put back in and recycle back up in the presynaptic nerve site. The faster you can do that, the faster you can recycle that signal. And so almost everything that I describe in that entire system improves and has been shown to, to, to increase with training. So that alone is given to give you benefits. We haven't even walked into to getting from an electrical signal now into an action potential which is going to cause a muscle contraction. So getting from nerve into the muscle, we see everything from improvements in what we call contractility, which means the muscle fiber themselves can produce more force or more velocity independent of muscle size changes. This is another component. When we ask like, well, how is it I got stronger without getting bigger? Well, in the muscle fiber itself, its ability to contract force increases. And this is because we have everything like the sarcoplasmic reticulum, which is the place that stores and releases the calcium, which is what's needed for this entire cross bridge interaction from the myosin and actin to happen. I know a lot of, I just lost a lot of people, but you can go look at some of these images. The sarcoplasmic matricium gets activated more, it gets more sensitive. It is better at releasing calcium, bringing it back in and doing it again. The bond between the cross bridge, the myosin and actin gets stronger. The calcium affinity is the phrase that we use there, increases. So we're literally walking through almost the entire process of skeletal muscle contraction here. And every step along the way we see improvement. So that net result is we see again more force production independent of any change in size, independent of any increase in contractile units. We didn't add anything to the equation, we didn't change size. We did nothing but improve efficiency effectively independent of that. Now we can actually start talking about changing muscle fiber type. So we can change our fibers from a slow twitch fiber to a fast twitch fiber. That alone is going to give you more force production. Again, independent of size. Fast twitch fibers tend to be larger than soul touch fibers, but not always, especially in the presence of endurance training. So if you do a lot of consistent endurance training, it's very common for us to find solch fibers that are as similar size, if not larger, often very often larger than the fast twitch fibers.

If you do a lot of slow.

Fibers, big, slow, very metabolically effective fiber. So extremely fatigue resistant. So it's not a bad thing to call them slow. We tend to say Fast is slow and slow has this negative connotation, but it's a quite healthy fiber type to have outside of that. Now we haven't even gotten into things like penation angle. So this is the angle at which your muscle fibers interact with your bone. So we tend to think about this as like a muscle fiber is pulling on a muscle. Well, some of these are oriented at almost a 90 degree, so a fiber runs perpendicular into the bone and some of them are closer to like a 45 degree and some of them are closer to almost parallel. And that confers a lot of unique mechanical benefits. So in one area it's actually going to increase force production. You go the other direction increases velocity. And so we have all kinds of changes in the angle at which the muscle inserts into the bone. Now we're already in the mechanic side of it, right? So we've, we've influence how effectively it pulls. And with any of these things it's always a give and take. So you're going to give up in the case of a nation angle, you're going to give up strength, but you're going to increase shortening velocity or if you want to increase the velocity, you're going to give up sort of the strength.

Right.

We haven't gotten to any of the energetics at all. So we haven't talked about increasing storage of phosphor creatine, which is the energy system needed to power that muscle contraction at the fastest possible rate. So we could continue to go as long as you want here, but hopefully you're getting the point of a little bit of the adaptations that occur. The reason I want to actually why I think that stuff is important to bring it back maybe for some listeners. I know I took you on a journey there and you're just like, what the hell just happened? That matters because again, this is the specific explanation for how is it possible that I got stronger but I didn't get bigger. And this is also why strength and hypertrophy are intertwined and are heavily overlapped, but are not necessarily the same thing. So for example, we can increase muscle size and actually reduce strength because of what's called lattice spacing. So what happens is you have to kind of remember your muscle fibers are these long cylinders and the way that they contract requires an optimal space. And so what happens is you have this molecule called actin and you have this molecule called myosin. Myosin sits in the middle and there are six actin that surround each individual myosin in a three dimensional circle. Here. So you got a myosin in the middle that has all these globular heads, and they can reach up and grab an Actin. And again, there's six sort of around them, right? Well, one of the things that can occur is if those. Those actin are too close together. So imagine my hands, I'm reaching out and doing a giant T, right? So I'm horizontal out there. Well, if my fingertips are the tips of the myosin, and I'm trying to reach up and grab an Actin, and I want to pull those actins closer to my face, well, those actins stack on top of each other, and that's what actually makes your muscles grow up. Like, if I flex my bicep, it actually grows up 3 or 4 inches because you're stacking these. These sarcomeres, or what they're called, on top of each other. All right, great. Well, if I'm reaching out to grab them and the muscle is stretched too far, I can't actually make that strong of a connection. It would be like if I reached out and grabbed something, but I can only reach my longest fingertip on it. When I go to contract, I can't make that strong of a contraction because my grip is weak. My grip's gonna break before I reach my strength limit. If I'm too close, there's nowhere to go. I'm already as close. So if you actually disrupt that lattice spacing too much, you can actually lose a little bit of strength. So it's not that getting bigger will ever make you weaker. It's simply that you're not optimizing for strength. You're simply optimizing for size. And so that can. That can explain a little bit of the discontinuity between growing and performance.

I'd like to take a brief break and acknowledge our sponsor, Athletic Greens. Athletic Greens is a vitamin, mineral, probiotic, and adaptogen drink designed to help you meet all of your foundational nutritional needs. I've been taking Athletic greens daily since 2012, so I'm delighted that they're a sponsor of this podcast. The reason I started taking Athletic Greens and the reason I still take Athletic Greens once or twice a day is that it helps me meet all of my foundational nutritional needs. That is, it covers my vitamins, my minerals, and the probiotics are especially important to me. Athletic Greens also contains adaptogens, which are critical for recovering from stress, from exercise, from work, or just general life. If you'd like to try Athletic Greens, you can go to athleticgreens.comhuberman to claim a special offer. They'll give you five free travel packs and they'll give you a year supply of vitamin D3K2. Again, if you'd like to try athletic greens, go to athleticgreens.com huberman to claim the special offer. What are a few of the major changes that occur in muscle, nerve, et cetera, when we experience hypertrophy? I've heard of protein synthesis changes. I'm assuming that's true. Maybe you can tell us a bit more about that. Changes in blood flow?

Yep.

Perhaps changes in neural innervation. Who knows, Maybe even changes in fascia. I'm not aware of any specifically, but I have to imagine that they're somehow involved.

Sure. So when we talk about hypertrophy, a lot of the adaptations are going to be similar because the mode of training is close enough. So your nerve probably aren't smart enough to differentiate.