Mike Israetel

You have vesicles of neurotransmitter. You pump enough of those in, you get the cool stuff of communication. You can run low on neurotransmitter. And then like the electrical signal arrives and neurotransmitter is like, sorry, not enough of us to do anything. And so you experience fatigue expressed as weakness.

And you need time to reconstruct a lot of those neurotransmitters, place them into vesicles. have those vesicles translocate to the synaptic cleft, and then like sit there and get ready. And that is a process that typically happens rapidly, but if you really exhaust it, can happen over some time. A really austere illustration of that is, and I've never done this, I've just heard about it.

And you need time to reconstruct a lot of those neurotransmitters, place them into vesicles. have those vesicles translocate to the synaptic cleft, and then like sit there and get ready. And that is a process that typically happens rapidly, but if you really exhaust it, can happen over some time. A really austere illustration of that is, and I've never done this, I've just heard about it.

I will take credit for doing many other drugs, but I've never tried ecstasy. But if you clear enough of that neurotransmitter, you don't feel the same the next day. You feel different. And it takes a day or two to get back up to those levels. Similar types of mechanisms are at work when you are going to very close to true failure on, let's say, a squat or a leg press.

I will take credit for doing many other drugs, but I've never tried ecstasy. But if you clear enough of that neurotransmitter, you don't feel the same the next day. You feel different. And it takes a day or two to get back up to those levels. Similar types of mechanisms are at work when you are going to very close to true failure on, let's say, a squat or a leg press.

I mean, you're cooking your muscles, but every single capacity of the nervous system to say push, push, push is at maximum capacity. And so you end up doing quite a bit of homeostatic disruption all the way along the axon, all the way through the cell body, and in the synaptic cleft, neurotransmitters getting everywhere, gunk building up.

I mean, you're cooking your muscles, but every single capacity of the nervous system to say push, push, push is at maximum capacity. And so you end up doing quite a bit of homeostatic disruption all the way along the axon, all the way through the cell body, and in the synaptic cleft, neurotransmitters getting everywhere, gunk building up.

That's going to take some time to fix, which is why we see typically that people don't regain their prior strength after fatiguing in resistance exercise for, depending on how hard you go, anywhere from several hours to several days.

That's going to take some time to fix, which is why we see typically that people don't regain their prior strength after fatiguing in resistance exercise for, depending on how hard you go, anywhere from several hours to several days.

And so if you have really, really hard workouts, it just might take several days for you to be able to have a really, really hard workout again for that same muscle group.

And so if you have really, really hard workouts, it just might take several days for you to be able to have a really, really hard workout again for that same muscle group.

Luckily, because a lot of this is peripheral nervous system-based and local musculature-based, if you train the living crap out of your chest one day and your triceps, you can train back and biceps, which have nothing much to do with those movements, pretty robustly the next day. Much of the fatigue is local. It's not all local.

Luckily, because a lot of this is peripheral nervous system-based and local musculature-based, if you train the living crap out of your chest one day and your triceps, you can train back and biceps, which have nothing much to do with those movements, pretty robustly the next day. Much of the fatigue is local. It's not all local.

The central nervous system – brain and spinal cord, specifically the brain – has a variety of mechanisms by which it controls your central fatigue. I remember I think Tim Noakes was a big proponent of the central governor model, though in the explicit terms which he described, it might not be the case or somewhat close. There's absolutely central governing going on.

The central nervous system – brain and spinal cord, specifically the brain – has a variety of mechanisms by which it controls your central fatigue. I remember I think Tim Noakes was a big proponent of the central governor model, though in the explicit terms which he described, it might not be the case or somewhat close. There's absolutely central governing going on.

And when your body can tell through a variety of mechanisms that, like, pretty messed up here, it's going to pull back on how hard you can do anything. And some of those neural structures might even be operating at full bore, but they're just degraded enough to where full capacity isn't full capacity anymore. And so in all those variety of ways and many others...

And when your body can tell through a variety of mechanisms that, like, pretty messed up here, it's going to pull back on how hard you can do anything. And some of those neural structures might even be operating at full bore, but they're just degraded enough to where full capacity isn't full capacity anymore. And so in all those variety of ways and many others...

your body, after accumulating a certain amount of fatigue, will need to back off. And if you think you can train ultra hard for the same muscles twice a day every day, you are welcome to try it. In medical supervised context, you won't last.

your body, after accumulating a certain amount of fatigue, will need to back off. And if you think you can train ultra hard for the same muscles twice a day every day, you are welcome to try it. In medical supervised context, you won't last.

So it's really good that we have breaks planned in, but it's also really cool because weight training is one of those things where you get a dose of it, and for days after, under the hood, it's upgrading your body. and your nervous system, and your muscles, and your tendons.