The Diary Of A CEO with Steven Bartlett - Most Replayed Moment: The Science Of Building Muscle Faster With Smarter Training - Dr. Mike Israetel

Episode Date: May 30, 2025

Dr. Mike Israetel breaks down the science of muscle growth and how to maximize your gains. Whether you’re new or experienced, learn key hypertrophy principles, effective training frequency, and why you don’t need endless gym hours to see results. Plus, discover how muscle memory helps you bounce back after breaks. Listen to the full episode here - Spotify - https://g2ul0.app.link/yjVHL6vrLTb Apple - https://g2ul0.app.link/qaWpqCyrLTb Watch the Episodes On YouTube - https://www.youtube.com/c/%20TheDiaryOfACEO/videos Learn more about your ad choices. Visit megaphone.fm/adchoices

You said there's two types of effective training. One of them is hypertrophy. Very good. And the other one is periodization. So periodization is the scientifically based organization of any kind of training that you want. Hypertrophy training is a type of training. It's just muscle growth training. It's like a fancy fucking science word for just getting more jacked, putting on muscle. That's the technical definition of hypertrophy.

And when you train for hypertrophy, you can do it kind of like by feel and more or less at random, and you'll get pretty good results in most cases. But to get your best results, you want that training to be periodized. Periodization is the scientific approach to how to organize your training to get sort

of roughly three things. Some of these are a bit more for athletes and not regular people. Get the best results that you can. Peak at an appropriate time, abs for summer. And minimize injury risk. And taking all the science that we know, that plan that you've made because you did it in an evidence-based fashion, that is now what've made because you did it in evidence based fashion, that is now what is considered a periodized plan. So that's how those two concepts relate to

each other. What do I need to know about hypertrophy in order to be able to achieve it? Is there anything really foundational? Because I think everyone wants a bit of muscle growth. I think I spend too long in the gym. I think I could be much more efficient when I'm training. What would you recommend that I start thinking about as foundational principles when it comes to hypertrophy muscle growth? One is specificity. It's the most important principle in all of sport training and exercise science is what am I here for? What do I want? Because you can do a bunch of exercises in the gym and you're like, that was great. And someone's like, are you getting the results you like?

And I'm like, well, what I want is a bigger bicep. Like how many bicep exercises do you do? Like I think upright rows, maybe. So I want a bigger bicep. If we just focus on me getting Stephen Butler a bigger left bicep. So specificities telling yourself, okay, I want bigger biceps and whatever X, Y, Z other muscles. Then we move in to the principle of overload, which means you have to challenge yourself. If most of your sets, someone else watching them, can't tell if you're warming up or doing what's called a working set, like a real set, you have a problem. So towards the end of all of your sets, either the weights are slowing down,

or even if it's the same speed, to you they feel perceptively harder. You know, you do this, this, this, and in a couple reps you're like, oh, that's what you want. Every real working set should be challenging. You should be approaching every real set with just a teeny, teeny dose of trepidation.

Like, oh boy, here we go. I'm gonna have to try. Once you have that. And a set is a group of repetitions. Correct. So if I do 10 repetitions, that's one set. One set, yeah. And so your sets have to be sufficiently heavy.

Anything between roughly five reps per set and 30 reps per set, where the last few reps are getting close to you not being able to use good technique and lift the weights, check plus. So there's not a set, a perfect amount of repetitions to do? There is. It's a trade secret and I'd have to say it off camera to you. Okay. NDA aside.

Okay, we're off camera. All right, great. So it's 17. So there's just tons and tons of contextual, nuance kind of stuff. Some of their muscles will seem to respond better to sets of 5 to 10. Other folks, even the same person could have muscles in their body that really respond better to sets of 20 to 30 and to everything in between. But generally, you get in the exercise science

data you'll have a group of people training for sets of roughly five reps and another group training for sets of roughly 30 reps and their change in muscle growth over 8, 12, 16 weeks is statistically undifferentiable. Which means if I delabel the groups and you don't know which one's which, you can't actually tell me who trained with higher reps or low reps. For muscle growth, it's roughly the same. That's so crazy. We're using the same weight. I'm guessing different weights. No, different weights. Yeah. A weight that is challenging for five reps is much heavier than a weight that is challenging for 30.

Okay. So I do wonder this all the time when I go to the gym. I wonder if I should be doing, I don't know, 30 reps of 10 kg on my bicep or I should be doing 10 reps of 20 kg. They're both right answers. No wrong answers there. And they both have the same chance of growing my muscles. As long as the strain that I experienced subjectively is difficult at the end of those sets. Okay. Interesting. Which is really good news because that's like another thing you

don't have to worry about. Which means at home, I can get any range of weights versus having to get really, really big ones to grow my muscles. As long as they're not so tiny that you're on rep number 45 and you're like, I could just do this for forever. Or they're not so enormous that you're like, I can't really even do two reps of this. Anything between roughly five and roughly 30 reps, challenging is really, really good. How many sets and how often do I have to visit the gym to get this bicep to grow? That answer depends on how much you've been doing before.

Okay. But if you're new to the gym, two sessions a week with two to three sets per session for your biceps is something that's gonna cause months and months and months of consistent progress. Really? Can you do more? Yes. Do you have to do as a beginner? No. Eventually as a more advanced person,

do you need to do more sets and perhaps more sessions to get consistently better results? Yes. But for beginners who haven't been to the gym very much or at all, the minimal effective dose is profoundly small, which is why I can say things like if you work out for 20 minutes twice a week, you're going to get great gains. What if I go to the gym and I do six sets on my biceps and I just go to the gym once a week? Does the distance between the workouts in a muscle group have an impact? Yes. Once a week training gives you good results, but twice a week training for the same muscle gives you notably better results. Training three times a week versus twice,

training four times a week versus three times, training five times a week versus four times is an exponentially deescalating amount of impressive differences. So one time a week works, it'll get you results. Two times a week gets you like one and a half times the results, like way better, better. Three times a week is like another little bit more results, still notable. Four times a week is like you got to be training for a while to notice the difference between three and four. Four and

five is contextual and nuanced and I can't actually tell you that categorically five days a week is better than four. There are some things I would have to know about your plan and everything else to make that conclusion. So really I want to be aiming at twice a week per muscle group. Twice is our minimum. Two to four times a week is what I say is kind of the best overall recommendation per muscle group. And if you train all of your muscles together at the same time, a whole body workout, which most people in the realm of just I'm busy and I can't train a lot, it would be all of the major muscles of your body in the same session twice or three times or four times a week. And that is an awesome beginner fitness plan.

What's going on in my muscles that's encouraging them and making them grow? And when are they growing? Is it when I go to bed at night? Is it when, do they grow the minute that I curl the dumbbell? What's actually going on? Because sometimes understanding what's actually going on inside helps me to think through

and change my behavior. Yeah. So the primary stimulus for muscle growth is there are molecular machines in your muscles, in your muscle cells, and they are designed to detect the presence of tension. And when your muscles generate tension, the molecular detector machines go, oh, we got tension here. And they start saying to other parts of the cells like, hey, let's get this muscle growth thing started.

Started. Not happening. Started. It's a stimulus of muscle growth. There are a couple of other mechanisms which might slash probably have an effect. And that a couple of them are metabolite sequestration, which is a very fancy way of saying the burn. You know at the end of a set you're like, the metabolites, the byproducts of training, if they accumulate to high levels, it's been shown in tons of animal studies and

a few human studies that like mechanistically they might also tell the molecular machinery that grows muscle for you again later, later, to get the muscle growth process. Another one is the pump. So you do a couple sets of biceps, you're like, oh my god, what's going on here, baby? Flash it at some girl, she runs away as usual. And the actual cell swelling itself might play a causal mechanistic role in generating more muscle growth. But we know it's probably at least 80% of the muscle growth anyone will see is because of those receptors for tension. Muscle growth as soon as you leave the gym is a negative because the gym is catabolic.

It breaks down your muscle. Actually training breaks down more muscle than it builds. However, as you go home and you start eating food, protein, carbs, fats, and you have several meals per day and you're resting, when the food's coming in, several hours after training begins, if you measure muscle growth consistently, which is really difficult to do, they don't do it super often, you have to keep people in the laboratory, you have to do radioactive tracers and measure all this weird stuff, every couple of hours they measure, the amount of muscle growth that's going on in the biceps goes up and up and up and up.

And it usually peaks about half a day to a day and a half after you lift, depending on how hard you went. If it's a pretty easy workout, it peaks a little sooner and dives and drops off about a day or two later. If you train really crazy hard, it'll peak like a day, day and a half later and then half a week later, it'll drop off back to baseline levels. But it's this really smooth curve

and you're growing muscle at every single point under that curve. So when you say, is it while I'm sleeping? Is it while I'm eating? Is it while I'm resting? The answer is all of those, except it's not at the gym. You don't grow muscle at the gym. You give yourself a signal to grow muscle at the gym.

And then what you do outside of the gym matters. So some people train really hard, they don't eat right. They don't eat enough protein. Their sleep is total, insert bad word here, and their stress levels are just totally psychotic. They train hard. And then week after week after week, they're like, not seeing any results.

Well, the results are actually created when you're resting, when you're sleeping, when you're eating nutritious food. They're stimulated in the workout, but that's just phase one. Phase two, the actual growth occurs outside of the gym and it occurs not at any specific time point, like a magic window of two hours after the gym.

Like that's when all the growth occurs. That's actually when it just starts to go up. It's four days afterwards. If you train twice a week, we train on Monday. You're growing a lot of muscle on Monday night, Tuesday and Wednesday. Back towards the end of Wednesday, you're just not really growing much more muscle. You go back to the gym Thursday, you hit it hard again. You hit that curve up by Sunday.

You're totally relaxed during Sunday. You're not growing any muscle. Your body's really recovering a lot of that fatigue. And then by Monday you're fresh as a pickle and you're ready to go at it again. How long will it take me to lose the muscles that I've gained if I don't go back to the gym? So again, focusing on this bicep.

I train it, I do two times a week, I get it nice and big. How long before it vanishes? Great question. Two part answer. Part one is within about two weeks of not training it, the first reduction in muscle that is detectable by modern machinery occurs. So if you don't lift for two weeks and we put you in an MRI scanner or a DEXA scanner, let's say a week and a half you don't lift, I can't tell.

You're not really losing any muscle yet. You're just going insane. And so me personally, I'm like addicted to lifting. So if I don't lift for a week, I'm like, oh my God, oh my God, all the muscles gone. And there is some kind of intuitive truth to that. Because when you don't stress your muscles, when you do stress your muscles, they get a little bit inflamed and they bulge up a little bit. So when you're not training for half a week to a week, your muscles look smaller, like they've lost weight, but it's really just all water that they lost. You do one gym session thinking like, oh my God, my biceps are gone.

A week and a half later, you do one session at the end of that you flex and you're like, oh my God, I'm the biggest I've ever been. I was just delusional that whole time. Cause that stuff comes back super quick. After about two weeks of not lifting, we start to lose muscle, but it happens really, really slowly and takes weeks and weeks and weeks and weeks after several months of not lifting. You're going to look considerably smaller in your biceps, but probably not as small as when you started lifting because your muscles have a certain memory,

if we can call it that. Is that true? That is a memory thing. Very true, oh yeah. And so a lot of times when you gain an initial amount of muscle, especially if you've been at it for years, it just never goes back to the same size

as when you started. It's just always gonna be bigger until you reach your 80s or something like that. That being said, yes, you will notice reductions in size. So two weeks is the direct answer there, and it's going to take weeks and weeks and months and months to recede. However, here's part two, and this is awesome news. Because of that muscle memory situation, however long it took you to gain the muscles initially,

it's going to take you an order of magnitude, a factor of 10-ish or so less time to get it back. If you've been more jacked before, if you've had bigger muscles, they come back to their old size. If you lifted for eight months, you got a bigger bicep and you stopped lifting for three months and it looks about the same as when you started. If you're really careful, it gets a little bit bigger, but really it's just back to square one.

Most people think, oh my God, another eight months just to get back to where I started? Like forget the gym. The truth is after roughly about a month, maybe as little as three weeks, you're gonna have the same size biceps that you did in your peak. Because the degree to which your tissue grows,

if it's been a certain size before, especially if it was notably bigger than normal, and you held that around for a few months and a few years, it comes back in a way that is so fast. If you experience it yourself, it's like you don't believe that it's happening to you. You gain back- Have they been able to scientifically test this? Oh yeah, all the time. Yeah. Retraining studies, You can't scientifically test this. Oh, yeah, all the time. Yeah. Retraining studies, detraining, retraining. Oh, yeah. They've,

they've done studies where they purposefully like lift for a while and they stop lifting for a long time and they see how long it takes to get back. And there's one study I'm familiar with offhand that there's a group of people that trained consistently for multiple weeks. And there's another group of people that trained consistently for a few weeks and then took two weeks completely off in the middle and then just started retraining again for a few weeks later. Both groups had identically sized differences in muscle at the end of the study. And so we were like, okay, so that group that trained consistently never took two weeks

off. Could we say that they purposefully like dunked two weeks of their time away for nothing? Uh-huh. Yeah, your body goes right back into regaining old lost muscle so rapidly that this is such great news because look, let's say you lifted consistently most of the year, holiday season comes up, winter holidays, you're not going to the gym as much,

maybe not at all. Three weeks later of no gym, you look at yourself, you look a little small or kind of deflated, and you're like, oh my God, I'm gonna have to restart all this from scratch. Nope. Two weeks later, you're in the best shape of your life again. If you left the gym for six months,

one or two months later, you're in the best shape of your life again. That's how rapidly it comes back. So it's really good news for anyone who hasn't been in the gym and is feeling guilty about it. Go back, get consistent again, you're just gonna skyrocket.