Welcome to the Huberman Lab Podcast, where we 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 is an Ask Me Anything or AMA episode, which is part of our premium subscriber content. Our premium channel was launched in order to raise support for the standard Huberman Lab Podcast channel, which still comes out once a week, every Monday, and of course is zero cost to consumer.

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Without further ado, let's get to answering your questions. And as always, I will strive to be as clear as possible, as succinct as possible, and as thorough as possible, while still answering as many questions per AMA episode as I can without these sessions becoming unreasonably long. I should also point out that if you asked a question and it was not answered this AMA, it may very well be answered in the next AMA.

So the first question, which had a lot of upvotes, meaning many people wanted the answer to this question, came from Jackson Lipfort. And the question was about so-called ultradian rhythms. For those of you that are not familiar with ultradian rhythms, ultradian rhythms are any rhythms that are shorter than 24 hours.

And typically when people ask about or talk about ultradian rhythms, they are referring to 90 minute rhythms. I've talked about these on the podcast before. And Jackson's question was, how do you use ultradian rhythms in your daily work? There's more to the question, but first off, I do use ultradian rhythms.

That is, I leverage the fact that these do exist in all of us as a way to engage in focused bouts of mental work once or twice, or sometimes three times per day. However, I use them in a way that's grounded in the research on ultradian rhythms for learning and memory in a way that might not be obvious just from their name, that they are 90 minute rhythms.

So I'll get into the details of how to use ultradian rhythms to best capture neuroplasticity, that is the brain's ability to change in response to experience, and in a way that should allow you to get one or two, or maybe even three focused bouts of learning per day, which can greatly accelerate learning of cognitive material, languages, mathematics, history for sake of school or work, or maybe just a hobby or a personal interest of some sort, and for skill learning in the physical domain as well.

Jackson then went on to ask, you've mentioned before that you try to include at least one 90 minute focus block per day as part of your work and overall mission. And indeed that is true. I try to get at least one of these focused ultradian rhythm blocks per day.

That is a period of about 90 minutes where I'm focused on learning something or doing something that's cognitively hard. Although typically I aim for two of these sessions per day. He then goes on to ask, what is the maximum number of blocks you can perform sustainably? The answer to that is probably four.

And I say probably because some people have schedules, lifestyles in which four 90 minute blocks of focused learning is possible per day, but that's highly unusual. For most people, it's going to be one or two, maybe three, four I would place in the really extraordinary end of things. Maybe if you're cramming for exams or you've managed to go on a writing retreat or a learning retreat of some sort, where you can devote essentially all of your non sleeping, non eating time to learning.

But most people simply can't organize their life that way. So the short answer is for me, it's one or two per day is the target and three would be the maximum. He then went on to ask, do you take vacations or extended breaks from these ultradian rhythm sessions? And the short answer is no.

Typically I try and do this every day. And yes, even on the weekends, but on the weekend, the ultradian rhythm focused learning bout might just be reading a book for about 90 minutes or so, which might not be as cognitively difficult as it is for other sorts of work that I performed during the week.

I occasionally miss a day entirely for whatever reason, travel obligations related to family, et cetera. But in general, I try and do this every day. I do think that the circuits for focus are, I guess the non-biological way to put it would be kept warm, but essentially that accessing the circuits for focus is made easier by accessing them regularly.

And that's because the circuits for focus are indeed themselves amenable to neuroplasticity In other words, the more you force yourself to focus, the easier focusing gets. I'll now answer the last part of the question, and then I will go through and emphasize some tools that anyone can use in order to leverage ultradian rhythms toward learning bouts, either cognitive learning or physical skill learning, or a combination of the two.

The last part of the question Jackson asked was, if you knew you needed to drastically increase the amount of focus you do daily, how would you schedule that focus and recover from it? That's an excellent aspect to this question. And I will now give you the details of how I would use and schedule ultradian rhythms.

I'll offer you a tool. I've never talked about this tool on the Huberman Lab podcast. And I will dispel a common myth about ultradian rhythms that points to a, believe it or not, an easier way to leverage them for maximum benefit. Okay, so as I mentioned before, ultradian rhythms are these 90 minute cycles that we go through from the time that we are born until the time we die.

Indeed, even during sleep, we are experiencing and more or less governed by these ultradian rhythms. This question and this answer is not so much about sleep, but just know that when you go to sleep at night until you wake up in the morning, every 90 minutes or so, your patterns of sleep, that is the percentage or ratio rather of slow wave sleep to light sleep to rapid eye movement sleep, changes in a way such that each 90 minute cycle gates the next cycle.

It sort of flips the on switch for the next 90 minute cycle, then that 90 minute cycle ends, flips the on switch for the next one and so on and so forth. I mentioned all that because during the daytime, the same thing is true, but most people don't know when the 90 minute ultradian cycles begin.

Because if you think about it, you could wake up on the basis of an alarm clock or noise in the room, or simply because you naturally wake up in the middle of an ultradian 90 minute cycle. So does that mean, for instance, that if you wake up 60 minutes into an ultradian cycle, that the next 30 minutes of your waking, right?

Because that 60 minutes needs to continue to 90 to complete an ultradian cycle, that the next 30 minutes after waking are related to the ultradian cycle that you were still in during sleep, or does it start a new ultradian cycle? And the answer is the former, that ultradian cycle continues even if you wake up in the middle of it.

And so a lot of people who want to leverage ultradian cycles for learning will say, well, how do I know when to start one? Does it start when I hit my stopwatch? Can I just set a clock and work for 90 minutes? And the short answer is no. And that might seem unfortunate, but the good news is that you can figure out when your first proper ultradian cycle of the day begins simply by asking yourself, when are you most alert after waking?

That is, if you were say to wake up at 7 a.m. and let's say that's the end of an ultradian cycle, or perhaps you're in the middle of an ultradian cycle, doesn't matter. What you need to watch for or pay attention to for a day or so is when you start to experience your greatest state of mental alertness in the morning.

And here we can discard with all the issues and variables around caffeine or no caffeine, hydrating or no hydrating. Exercise is one variable that we'll consider in a moment, but here's the deal. These ultradian cycles are actually triggered by fluctuations in the so-called glucocorticoid system, the system that regulates cortisol release.

And as some of you have probably heard me say before, cortisol, even though it's often discussed as a terrible thing, it's chronic stress, cortisol, cortisol, et cetera, cortisol is essential for health. And every day we get a rise in cortisol in the morning that is associated with enhanced immune function, enhanced alertness, enhanced ability to focus, so on and so forth.

In fact, the protocol that I'm always beating the drum about that people should get sunlight in their eyes as close to waking as possible, that actually enhances or increases the peak level of cortisol that's experienced early in the day. And that sets in motion a number of these ultradian cycles.

So for instance, if you wake up at 7 AM and you find that for the first hour after waking, you tend to be a little bit groggy or you happen to be groggy on a given day, but then you notice that your attention alertness starts to peak somewhere around 9.30 AM or 10 AM, you can be pretty sure that that first ultradian cycle for learning is going to be optimal to start at about 9.30 or 10 AM.

How can I say about if it's indeed a 90 minute cycle? Well, this is really where the underlying neurobiology in these ultradian cycles converge to give you a specific protocol. The changes in cortisol that occur throughout the day involve, yes, a big peak early in the day, if you're getting your sunlight and caffeine and maybe even some exercise early in the day, but typically that peak comes early and then across the day, the baseline jitters a little bit.

It comes down, but it bounces around a little bit. It's not a flat line if we were to measure your glucocorticoid levels. Each one of those little bumps corresponds to a shift in these ultradian cycles. So if you find that you are most alert at 9.30 or starting to become alert at 9.30 and then typically you have a peak of focus and concentration around 10 AM, that is really valuable to know because the way that the molecules that control neuroplasticity, that is the changes in neurons and other cell types in the brain that allow your nervous system to learn and literally for new connections to form between neurons, which is basically the basis of learning, those fluctuate according to these ultradian cycles.

What does this mean? This means if your peak and alertness and focus and energy could even be experienced as physical energy occurs at about 9.30 AM, I would start your first ultradian cycle for learning somewhere around there. Certainly 9.30 AM would be ideal, but 10 AM would be fine as well.

And then you have about one hour to get the maximum amount of learning in even within that ultradian cycle. This is where there's a lot of confusion out there. People think, oh, ultradian cycles are 90 minutes. Therefore we should be in our peak level of focus throughout that 90 minutes.

In reality, most people take about 10 or 15 minutes to break into a really deep trench of focus. And then periodically throughout the next hour, they'll pop out of that focus and have to deliberately refocus. This is why, if possible, you want to turn off wifi connections and put your phone in the other room or turn it off.

If you do need your phone or wifi, just be aware of how distracting those things can be to getting into a deep trench of focus. But the point is this, these 90 minute cycles occur periodically throughout the day, but there is going to be one period early in the day.

And here I'm referring to this period as starting at about 9.30 or 10 AM. And then likely another one in the mid to late afternoon that are going to be ideal for focused learning. And that focused learning about should ideally have you set your clock, a stopwatch or something to measure 90 minutes.

But do assume that there's going to be some jitter at the front end where you're not going to be able to focus as deeply as you would like. Then you'll get about an hour of deep focus. And then you really start to transition out of these ultradian cycles. How do you know when the afternoon ultradian cycle occurs?

Well, just as in the morning it occurs because there's a brief but significant increase in the glucocorticoid system in the mid to late afternoon. I wish I could tell you it's going to be 2 PM or it's going to be 3 PM. That's really going to depend on the individual when you ingest caffeine, some of the other demands of your day.

But you can learn to recognize when these two periods for optimized learning will occur. And here are the key principles. Watch for a day or two, meaning pay attention to when you have your peak levels of physical and mental energy in the morning. That is between waking and noon.

And then again, between noon and about 6 or 7 PM. Although I'm sure that there are some late shifted folks that will experience their peak and focus somewhere around 6 or 7 PM, especially if they're waking up around 10 or 11 AM as I know some people out there are.

Once you know where those peaks and focus occur on your schedule, set a stopwatch for one ultradian cycle in the early part of the day. In this example, I was saying 9.30, but if you can't hop on it until 10, that's fine. Set it for 90 minutes, consider that block wholly, meaning rule out all other distractions, but assume that within that 90 minute block, you were only going to be able to focus intensely for about one hour.

And just know that the molecules that control neuroplasticity and these things have names and yes, brain derived neurotrophic factor or BDNF is sort of the most famous of those, but there are others as well. In fact, the very receptors that control synaptic strength, the connections between neurons, some of the neurotransmitters and neuromodulators involved in synaptic plasticity, they undergo regulation by these ultradian or changes in glucocorticoid.

And then try and capture a second ultradian learning block in the afternoon. Again, just knowing that the first 10 or 15 minutes, consider it mental warmup, and then you get about an hour, it's not exactly 60 minutes, but about an hour to maximize learning. So if you're trying to learn something, really capture it during that phase as well.

Now, is there a third opportunity or a fourth opportunity? This relates to Jackson's question directly. And the short answer is not really. Unless you're somebody who requires very little sleep, within the 12 or 16 hours that one tends to be awake during the day or 18 hours that one tends to be awake, there are really only two of these major peaks in the glucocorticoid system that trigger the onset of these circadian cycles.

Again, there's sort of a ramping up and a ramping down of glucocorticoids throughout the day. But the real key here is to learn when you tend to be most focused based on your regular sleep wake cycle, caffeine intake, exercise, et cetera. And again, that's going to vary from person to person.

And you really only have two opportunities or two ultradian cycles to capture in order to get the maximum focus, challenging work done, AKA learning. So for somebody that wants to learn an immense amount of material or who has the opportunity to capture another ultradian cycle, the other time where that tends to occur is also early days.

So some people by waking up early and using stimulants like caffeine and hydration or some brief high intensity exercise can trigger that cortisol pulse to shift a little bit earlier so that they can capture a morning work block that occurs somewhere, let's say between six and 7.30 AM. So let's think about our typical person, at least in my example, that's waking up around 7.00 AM.

And then I said, has their first ultradian work cycle really flip on 'cause that bump in cortisol around 9.30 or 10.00 AM? If that person were say to set their alarm clock for 5.30 AM, then get up, get some artificial light. If the sun isn't out, turn on brighter artificial lights, or if the sun happens to be up that time of year, get some sunlight in your eyes.

But irrespective of sunlight, we're to get a little bit of brief high intensity exercise, maybe 10 or 15 minutes of skipping rope or even just jumping jacks or go out for a brief jog. What happens then is the cortisol pulse starts to shift earlier. And so the next day and the following day and so on and so forth, provided they're still doing that exercise first thing and ideally getting some light in their eyes as well.

Well, then they have an opportunity to capture an increase in cortisol that is now shifted from about 7.00 AM to about 8.30 AM. So they can capture an hour of work there and then they will also still be within that rising phase of cortisol in the 9.30 to 10.00 AM block that lasts until about 11.30 or so.

They might have lunch, perhaps after lunch, they do a non-sleep deep rest, maybe they don't, maybe you're a napper, maybe you're not, doesn't really matter. And then in the afternoon, and I would suspect it would now be in the earlier afternoon, sometime around two or 2.30 would be typical.

Although again, that exact time will vary person to person, then they would want to schedule another 90 minute work block. So that's how you can capture three. Now you can start to see also why capturing four ultradian work blocks would be exceedingly rare. It's just not typical that people are awake for that much of the day, you have to sleep at some point.

And I should mention that if you're going to force yourself to wake up earlier on a consistent basis, you probably should be trying to get to sleep a little bit earlier as well, because it's not just the quality, but the duration of quality sleep that really matters for learning.

And I should also remind everybody that the actual rewiring of neurons does not occur during any focused work block. It actually occurs during deep sleep the following night and the following night and during non-sleep deep rest. This is why non-sleep deep rest can accelerate learning because it's in states of rest that the actual connections between neurons strengthen or weaken or new neurons are added in a way that allows for what we call learning.

Okay, so one or two ultradian work blocks per day is typical, three would be really exceptional and four would be extraordinary. Look for them, meaning look to see when you are feeling most focused and alert, typically in the period before waking and noon, and typically in the period between noon and bedtime, given your standard intake of caffeine and exercise and other life events.

Please also remember that even though it's an ultradian 90 minute work block, the neuroplasticity is going to be best triggered within a 60 minute portion of that. And there's no way to know exactly when that 60 minutes begins and ends until you actually begin the work block. So this is really designed to be empirical.

You need to actually go do this. What you'll notice again is that it's hard to focus at first, then you'll drop into a state of focus. You may get distracted, that's perfectly normal. You refocus, get back into triggering learning. That's really what you're doing. You're triggering learning and then there'll be some taper and then you'll be out of the ultradian work block.

Now it's also key to understand that myself and other people should not expect that they're only working during these 90 minute work blocks. It's just that a lot of the sorts of demands of our day, including, you know, cooking and shopping for groceries and email and text messaging and social media, a lot of those things don't require intense focus of the sort that I believe Jackson is asking about maximizing and that I'm referring to when I talk about these ultradian work blocks.

And then as a final point, I've been talking about these ultradian work blocks and focus, et cetera, in a context that brings to mind ideas about cognitive work. So learning a language, learning math, writing or creating, doing something related to music, et cetera. But these 90 minute ultradian work blocks also directly relate to physical skill learning as well and to physical exercise as well.

So if you are somebody who's really interested in improving your fitness and your fitness requires a lot of focused attention. So for instance, when I go out for a long run on Sundays, which is part of my fitness routine, I'm deliberately not thinking about much. I'm just trying to cruise along.

I might focus a little bit on my pace and stride, maybe an audio book I'm listening to or a podcast, but typically I'm just kind of cruising along. It's low cognitive demand work. These ultradian work blocks can really be maximized for pure cognitive work. So kind of book type work, et cetera, music, et cetera, or they can also be leveraged toward skill learning.

So if you're trying to learn how to dance or how to perform a particular athletic move, or you're trying to get better at some skill that requires a lot of focus and alignment of muscular movement and cognitive demands, et cetera, well then these are also going to be ideal for triggering neuroplasticity to get better in the motor skill based domain as it's called, et cetera.

If you'd like to learn more about ultradian shifts in neuroplasticity and ultradian work bouts, I will certainly do more on this in the Standard Huberman Lab podcast, but the keywords to look up, if you want to explore this further online, it's not something that a lot of people know about, it's called iterative metaplasticity.

It's a vast literature and one that I'd be happy to teach you in a standard podcast episode. But in the interest of getting to more questions from you all, hopefully the answer I've given you now has been complete enough, yet clear enough, and yet succinct enough that you can start to leverage these really powerful aspects of iterative metaplasticity and ultradian rhythms for learning.

And I'd just like to point out that these opportunities for focused learning that occur in these 90 minute ultradian cycles are really terrific opportunities. They are offered to you at least twice every day, and you can really learn to detect when they occur and when they're likely to occur.

You can certainly learn at other times in the 24 hour cycle, but for anyone who's tried to stay up late at night cramming for an exam, or for somebody who's tried to learn during the sleepiest time of their afternoon, we can be very familiar with the fact that there are times of day in which we are best at learning and as I've just described, there are ways to capture those moments and they are valuable moments.

So even though it's just about three hours per day, or really only two hours per day 'cause of the 60, 90 minute thing that I talked about a few minutes ago, learn to know when these occur and really treat them as valuable, maybe even wholly in the sense that they are really the times that are offered up to you each day by your own biology in ways that will allow you to get better pretty much at anything.

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