The Science of Ultradian Rhythms

Most bodily processes operate on a 24-hour cycle known as the circadian rhythm, which governs sleep-wake transitions and regulates vital functions like temperature, blood pressure, hormones, hunger, and digestion.

On a smaller scale, we also have ultradian rhythms, which recur within a single day and have shorter cycles than circadian rhythms.

The term ultradian means "many times a day." The most significant ultradian rhythm for performance is the 90-minute cycle.

In the 1950s, sleep researcher Nathaniel Kleitman identified that humans experience 90-120 minute cycles throughout our lives, which he termed the "basic rest-activity cycle."

These cycles reflect various sleep stages at night (alert, light, REM, deep sleep, etc.), and during the day, they manifest as fluctuations in energy and alertness.

Now, you may have encountered the idea of prioritizing energy management over time management. While some might dismiss it as merely another productivity gimmick, research supports this concept:

We are biologically tuned for focus and attention within these 90-minute cycles. This applies to cognitive tasks (like writing or music) and skill acquisition (like dance or athletic moves).

Despite this, many of us overlook our natural rhythms, ignoring the body's innate signals for breaks.

Our bodies are designed to work in short bursts, followed by rest, rather than maintaining constant effort throughout the day. Though it’s possible to focus for several hours, it contradicts our biological underpinnings.

By recognizing and utilizing your ultradian rhythms, you can enhance productivity by working when your body is primed and taking breaks when needed.

So, how can you apply this knowledge to your routine? How do you identify the start of a 90-minute learning session?

Utilizing Your Ultradian Rhythms

There's good news and bad news.

Let’s start with the downside: Ultradian cycles typically last about 90-120 minutes, meaning you might wake up mid-cycle, and that cycle will continue regardless of your wakefulness.

Therefore, it’s advisable not to dive straight into focused work upon waking.

The upside?

You can determine when your first ultradian cycle of the day begins by asking, "When do I feel most alert after waking up?"

Monitor yourself for a few days to identify when your physical and mental energy peaks, considering your usual caffeine intake and exercise routine:

• In the morning: Between waking and noon
• In the afternoon: Between noon and bedtime

For instance, if you wake up at 7 am, you might feel a bit groggy for the first hour, but notice increased alertness around 9:30-10 am.

This suggests that your first ultradian cycle for learning kicks in around that time.

Why “around”?

These cycles are influenced by fluctuations in the glucocorticoid system, which regulates cortisol release.

While often viewed negatively, cortisol is essential for health, peaking in the morning to enhance immune function and alertness.

Throughout the day, cortisol levels fluctuate, reflecting shifts in ultradian cycles.

(A quick tip from Huberman: Exposing your eyes to sunlight shortly after waking boosts morning cortisol levels.)

If you find peak alertness around 9:30 am and focus peaks around 10 am, you should schedule your first bout of focused work during that window.

This pattern will vary for everyone, both in timing and the number of cycles they can effectively manage.

Typically, most people can handle 1-3 x 90-minute intervals daily, depending on sleep quality, nourishment, and focus training.

While completing 4 x 90-minute focused sessions daily is possible, it’s not common.

Some may think, "This is absurd; I can work for hours. My job demands I sit behind a computer for at least 10 hours."

That was my initial response too.

However, we’re discussing 'deep' work that requires high levels of focus and concentration, not routine tasks like replying to emails.

We're focusing on work that promotes neuroplasticity. Anyone can sit at a screen for hours, but is it fostering long-term brain changes?

Now, let's delve into the structure of one focused session.

The Structure of a Focused Session

It's crucial to understand that according to Huberman, there’s a common misunderstanding about how these 90-minute cycles function.

You won’t experience full peak performance throughout the entire 90 minutes.

Most individuals require 5-15 minutes to reach deep focus—consider it a warm-up.

Following this, you have about an hour to maximize learning, which is your peak performance window. Although this is an ultradian block, neuroplasticity is best triggered within this 60-minute segment.

You won’t know exactly when this 60 minutes begins or ends until you begin the session.

Your focus may waver, which is entirely normal. The key is to continually redirect your attention, an active process that demands considerable metabolic energy, making it essential to minimize distractions.

(A simple suggestion: Keep your phone out of sight! If it’s within your line of vision, your brain expends energy trying to ignore it.)

Your brain and body consume significant amounts of oxygen, glucose, and other nutrients, leading to a natural taper towards the end of the cycle, signaling the end of your work block.

After this, it's crucial to rest.

Improving focus is equally about what you do after the focused session as it is about what you do during it.

Prioritizing Breaks and Sleep

A break of 20 minutes is optimal, but any pause (even 5 or 10 minutes) is beneficial.

You don’t need to sleep or simply stare at the ceiling; engaging in automatic tasks allows your mind to wander.

Avoid intensive reading or screen time during breaks.

Make an effort to decompress, as it will enable you to return to intense focus sessions throughout the day.

Ignoring your body’s signals and pushing through low-energy periods will eventually lead to diminished focus and productivity.

You’ll still accomplish tasks, but not as efficiently, and you’ll likely feel drained by the end.

The significant takeaway:

Neuroplasticity occurs during waking states, but the actual rewiring of our neural pathways happens during sleep and deep rest.

This insight implies that striving to keep your brain at maximum capacity at all times or sacrificing sleep for productivity is counterproductive.

As my favorite anti-productivity guru Oliver Burkeman wisely states: > The truly valuable skill here isn’t the capacity to push yourself harder but to stop and recuperate despite the discomfort of knowing that work remains unfinished, emails unanswered, other people’s demands unfulfilled.

Key Takeaways

Whether you are awake or asleep, your life unfolds in these cycles.

They are so vital for learning and memory that Huberman incorporates these ultradian sessions daily—even on weekends.

On leisure days, his learning might include something light, like reading, but he still adheres to the 90-minute cycle.

Why?

The neural pathways for focus respond to neuroplasticity, meaning the more you train your focus, the easier it becomes.

I’ll be honest; I aim to be mindful of these cycles without becoming overly fixated. Some days, I feel ready to dive into work right after waking; other days, I need time to gather my focus.

I may write for two hours one day and struggle to maintain focus for 15 minutes the next.

Recognizing how these cycles function and remaining aware of them is valuable.

Here are some critical takeaways for my future work approach:

1. Recognize when to stop. Often, when I feel unproductive, I push through even when I’ve reached the point of Diminishing Returns. (The Law of Diminishing Returns indicates that beyond a certain point, additional effort yields progressively less benefit.)

Even if I feel capable of doing more, I need to take a break.

2. Take genuine breaks. It feels counterintuitive to pause when on a roll. However, understanding the science behind neuroplasticity motivates me to ensure I take meaningful breaks.

I’ll compile a list of simple tasks to do during breaks—putting away laundry, making calls, or quick errands—to keep me moving.

3. Eliminating distractions is essential. Protecting my focus is vital, as even minor distractions can derail my concentration. Keeping my phone out of sight is crucial.
4. Practice patience. It generally takes 10-15 minutes to enter deep focus. Knowing this helps me persist with a task instead of abandoning it because I’m not feeling it.
5. Understand you’re not lazy. There will be days when I achieve little, and I can be harsh on myself during those times. It’s important to realize that low energy isn’t laziness; it’s a normal biological rhythm with fluctuating energy levels.

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