RISE Sleep Tracker
One of Apple's Best Apps of 2024

Your Biological Clock: There’s a Right Time to Do Everything

By working with your biological clock’s sleep-wake cycle and daily energy peaks and dips, you’ll be able to feel and function your best each and every day.
Reviewed by
Jeff Kahn, M.S., Rise Science Co-Founder
Our Editorial Standards
We bring sleep research out of the lab and into your life. Every post begins with peer-reviewed studies — not third-party sources — to make sure we only share advice that can be defended to a room full of sleep scientists.
Learn more
Updated Regularly
We regularly update our articles to explain the latest research and shifts in scientific consensus in a simple and actionable way.
Illustration of a person's head with biological clock embedded in it

Did you know that your body has a built-in biological clock? This clock signals to your body when it’s time to perform your everyday necessities, from sleeping to eating.

Learning what the biological clock is and how it operates relative to the sleep-wake cycle can help you determine your ideal wake and sleep times — so you can get the amount of sleep your body needs for better energy during the day. More than that, understanding how your daily energy levels fluctuate can help you structure your day to maximize everything that matters to you — productivity and feeling good being the top two on everyone’s list.

What Is a Biological Clock?

All living organisms, from fruit flies to killer whales, have biological clocks that regulate their biological rhythms — or repetitive biological processes. Your circadian rhythm, which tells your body when to be active and inactive over a roughly 24-hour cycle, is one of these biological rhythms. 

While you’ve likely heard talk of your biological clock, it’s actually not just one internal clock. There’s an entire network of peripheral clocks distributed across your organ systems and cells. At certain times of day and night, and according to internal and external cues, these clocks kick off predictable biological processes, like hormone production, temperature regulation, blood pressure, and the most well-known of all — your sleep-wake cycle (more on that later).

However, all of us do have a master biological clock (or circadian clock pacemaker). This is also known as the suprachiasmatic nucleus (SCN) — a group of neurons located in the part of the brain called the hypothalamus. 

The SCN is roughly attuned to the 24-hour light cycle, in which light (the most important circadian cue for humans) prompts the master clock to alert the rest of your body’s biological clocks. Working as a team, these internal clocks tell you the best times for waking, sleeping, eating, exercising, and so on — creating a complex but predictable pattern to your everyday life.

How Your Biological Clock Influences Your Sleep-Wake Cycle

biological clock: illustration of a person and a clock

Now that you have a good idea of what the biological clock is and how the internal clock network regulates your biological rhythms to influence your daily activities, let’s zero in on the sleep-wake cycle.

Your sleep-wake cycle is governed by the two laws of sleep: sleep homeostasis and circadian rhythm. These two laws operate independently but also interact with each other to determine when you go to bed and wake up, as well as your daily energy fluctuations.

To understand sleep homeostasis, we first need to look at how your body’s adenosine levels change relative to the sleep-wake cycle. During wakefulness, adenosine (a drowsiness-inducing compound) builds up in your brain, leading to rising sleep pressure. Consequently, you fall asleep at night, and your body purges the accumulated adenosine during slumber, resetting the sleep homeostat to zero the next morning. 

Listening to your biological clock to go to bed and wake up at the ideal times for you will help keep the sleep homeostat balanced. You’re more likely to meet your sleep need (the genetically determined amount of sleep your body needs) and keep sleep debt low (the amount of sleep you’ve owed your body over the past 14 days and the number that best predicts how you feel and function every day).

Meanwhile, your master biological clock regulates your circadian cycle through various clock genes. That said, the circadian rhythm is also influenced by external factors, of which light exposure is the most important of all. Both natural and artificial light can maintain or upset your circadian cycles — the latter incites circadian misalignment that often presents itself in situations like:

  • Social jetlag (a mismatch between your social and biological clocks)
  • Travel jet lag when in a new time zone
  • Shift work

An out-of-whack body clock doesn’t just bring about low energy levels and sleep disorders. Circadian misalignment can also cause serious health consequences over time, such as heart disease, diabetes, and obesity. It’s even associated with mental health issues like bipolar disorder.

As such, working with your biological clock to keep your circadian rhythm on the right track is vital for circadian alignment, the foundation for better energy levels and overall wellness.

Working With Your Natural Energy Fluctuations

If you’re wondering how to take advantage of your sleep-wake cycle to feel and function at your best, RISE can help. 

First, the app is purpose-built to tell you the ideal times for sleeping and waking to ensure you’re meeting your sleep need and minimizing sleep debt. Secondly, it shows you how to structure your day according to your energy peaks (the times at which you’re primed to be alert and productive) and dips (the times at which you’re inclined to rest and refuel). The exact times of these peaks and dips can be found on the “Energy Schedule” in the app. 

Although these timings may vary from person to person, the general pattern is largely the same. Here are the energy fluctuations you can expect to experience each day and how you can use them to your advantage.

Wake Up

Upon waking up (RISE calls it your “Wake Zone” in the app), adenosine — the drowsiness-inducing chemical that accumulates during wakefulness and is gradually purged during sleep — is still present in minute amounts, making you feel groggy.

P.S. Wake-up grogginess is completely normal even if you’ve met your sleep need last night. In fact, scientists term this natural phase of the sleep-wake cycle as sleep inertia.

Morning Ramp-Up

biological clock: bed with white sheets

As you slowly transition out of morning sleep inertia (which can take up to 90 minutes), light exposure prompts the SCN to release circadian-alerting signals in steadily increasing amounts and to neutralize drowsiness. Cortisol, norepinephrine, and serotonin also flood your body to promote wakefulness and alertness. This potent cocktail of chemicals and hormones banishes the last dregs of morning inertia from your system, helping you to feel more energetic.

P.S. This is the best time to sip on a cup of joe and shorten your grogginess zone.

Morning Peak

The cresting levels of circadian-alerting signals, coupled with a surge in cortisol, norepinephrine, and serotonin, leads to what RISE calls your “Morning Peak,” i.e., your first energy peak of the day. The app tells you the exact window of time to schedule A-game tasks for peak productivity. Keep in mind that at the same time, adenosine will start to creep back into your system, and sleep pressure slowly builds up.

P.S. A high sleep debt will inevitably lower your energy peaks and deepen your dips.

Afternoon Dip

From the early to late afternoon, there’s a temporary lull in your body’s circadian-alerting signals. This allows the burgeoning sleep drive to temporarily overpower your circadian system. You may feel sluggish and/or drowsy as you experience what’s known as the “Afternoon Dip” in the RISE app.

Contrary to popular belief, your energy dip isn’t a direct result of your lunch (although a meal full of processed carbs can worsen the effects of the afternoon slump). Nor does it have to be unproductive — research shows energy dips may be a productive outlet for tackling creativity-based tasks. Alternatively, stack passive tasks like administrative work and household chores to make the most of your dip.

P.S. This is the best time to take a nap and catch up on sleep without disrupting your bedtime that night.

Evening Peak

Your circadian-alerting signals start to pick back up again to try to combat the ever-rising sleep pressure that is now at an all-time high. This leads to your second energy peak of the day — RISE refers to it as your “Evening Peak.” Take advantage of it to end off the day on a productive note.

P.S. Scientific evidence shows a 17.6% boost in lung efficiency nearer to the evening times (i.e., 4-5 p.m.). This, coupled with the peak in your core body temperature, suggests that exercising during this window of time may yield your best personal record yet.

Evening Wind Down

As darkness falls, your circadian-alerting signals start to quiet down for the night. Your sleep drive is once again in the driver’s seat, thanks to a build-up of adenosine. It’s time to wind down, relax your mind and body, and get ready for bed.

P.S. Take advantage of the “Evening Routine” habit in the RISE app to customize your ideal evening wind down as part of your bedtime routine.

Melatonin Window and Bedtime

RISE app screenshot of melatonin window reminder
The RISE app shows your Melatonin Window to let you know your ideal window of time for going to bed.

In the 2-3 hours leading up to your biological bedtime, the master clock switches gears and tells the pineal gland in your brain to start producing melatonin (a sleep-promoting hormone). Scientists term this biological process the dim light melatonin onset (DLMO), which marks the start of your “Melatonin Window” in the RISE app. Do note that your Melatonin Window shifts daily based on your recent sleep times and other fancy RISE algorithms.

Go to bed within this window of time to take advantage of your body’s peak melatonin levels. You’re far less likely to stay up counting sheep, and instead, more prone to falling asleep quickly and staying asleep throughout the night. Aligning your target bedtime with your Melatonin Window gives you the best chance of meeting your sleep need to keep sleep debt low.

P.S. Add the “Melatonin Window” habit to your “Energy Schedule” in the app to give you a heads up on when you should hit the sack every night.

The Trick Is to Work With Your Biological Clock

Running on a full energy tank isn’t about downing energy bars or drinking coffee all day long. Instead, it’s about working with your biological clock and circadian rhythm to get the sleep you need and to do the things you need to do at the right times.

The reality is, your body is already timed to an optimal schedule for healthy sleep and better energy; you just need to listen to your internal clock. Of course, a tool like RISE makes it much easier to know when your energy peaks and dips will be, right down to the exact minute. Use the RISE app to help you feel and function at your best every single day.


Sleep better. Sell more.

Learn more about Rise for sales teams.

Thanks! We received your information. You'll hear from us shortly.
Oops! Something went wrong while submitting the form.
About Rise
Rise is the only app that unlocks the real-world benefits of better sleep.

Instead of just promising a better night, we use 100 years of sleep science to help you pay down sleep debt and take advantage of your circadian rhythm to be your best.

Over the past decade, we've helped professional athletes, startups, and Fortune 500s improve their sleep to measurably win more in the real-world scenarios that matter most.

Rise Science is backed by True Ventures, Freestyle Capital, and High Alpha; investors behind category winners Fitbit, Peloton, and Salesforce Marketing Cloud.

Circadian Rhythm

View all
Try 7 days free

The power behind your next best day

RISE makes it easy to improve your sleep and daily energy to reach your potential

RISE app iconApp store icon