Science
July 21, 2023
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Circadian Rhythm: What It Is & How It Affects Us

What Is a Circadian Rhythm?

Ever heard of chronobiology? It’s the scientific study of time and how it relates to our brains and bodies, and at the centre of that science is something called the circadian rhythm. Circadian comes from a combination of the Latin words circa meaning “approximately” and diem meaning “day”, and circadian rhythm is the phrase we use to describe the natural sleep/wake cycle of organisms (including humans) over a twenty-four hour period.

The 24 Hour Clock & Circadian Rhythm

If you thought the twenty-four hour clock was a human invention—think again. Turns out, it’s as natural as sleeping or breathing and has been around for millennia. Our cells run on a twenty-four hour cycle, telling us when to sleep, and when to eat. 

The Greek philosopher Theophrastus first noticed Circadian rhythm in a tree which opened and closed its leaves over the course of a day; the tree would close its leaves every night and begin opening them again in the morning.

As it happens, humans operate quite similarly to Theophrastus’s tree. In 1961, Frenchman Michael Siffre descended into a cave to find out what happens to the human psyche when we live without exposure to the outside world. Planning to stay for two weeks, he ended up spending 25 days in the cave, and proved that humans, like other organisms, have an internal biological clock. 

Although Siffre’s clock was extended slightly (by 30 minutes) when isolated from the day/night cycle of the earth, Siffre ate and slept when his body told him to, and the patterns of his behaviour conformed to a 24 hour period—a circadian rhythm.

How Does Circadian Rhythm Affect My Sleep?

Your circadian rhythm runs in the background without you ever having to think about it, so your body will naturally feel tired at some point over the course of twenty-four hours. But optimizing your sleep schedule to sync with your circadian rhythm can actually improve your sleep and help you feel more rested. You can even adjust your circadian rhythm (for example, in order to go to bed or wake up at different times), but experts say you’ll need to do it incrementally, over time.

While Siffre demonstrated that our circadian rhythm continues to function in the absence of external stimuli, there are some things that have been proven to aid our bodies in keeping our circadian rhythm on track. Natural light, for example, informs our bodies that it’s time to wake up and be active; while darkness can make us feel drowsy.

That’s part of the reason you hear people saying we should put our phones away a few minutes before trying to sleep, and why many people have trouble sleeping in a well-lit room. Nighttime (or the illusion of it) helps our circadian rhythm put us to sleep.

How Does Circadian Rhythm Affect My Workflow?

We all have a most productive time of day—the time of day when we feel most energized to do our work—and this too, has to do with our circadian rhythm. Based on when we go to sleep and when we wake up, we can either feel energized or tired, motivated or unmotivated.

Getting in touch with your circadian rhythm means figuring out your ideal bedtime, sleep length, and wake up time. And once you’ve nailed that down and feel good about the amount of rest you’re getting, you can further determine the times when you feel most motivated to get work done. 

For example, perhaps it takes you some time to “warm up” for your day, so it’s best if emails are handled in the morning, whereas major projects are something you tackle in the afternoon or late at night. 

Your peak productive hours are actually tied to your circadian rhythm, and if you can manage to sync your prime working hours with when your body feels most active, you may start to get more done in the run of a day.

Conclusion

Scientists are still working out exactly how our circadian rhythms work and how they affect us day-to-day, but there’s certainly proof out there that humans run on a 24 hour clock—independent of any alarms, sundials, or wrist watches. Our sleep/wake schedule is important to how we operate as humans, and learning about your own circadian rhythm can help you nail down a healthy sleep schedule and more productive work schedule.

The Power of Habits
Charles Duhigg
With penetrating intelligence and an ability to distill vast amounts of information into engrossing narratives, Duhigg brings to life a whole new understanding of human nature and its potential for transformation.
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Circadian Rhythm: What It Is & How It Affects Us

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What Is a Circadian Rhythm?

Ever heard of chronobiology? It’s the scientific study of time and how it relates to our brains and bodies, and at the centre of that science is something called the circadian rhythm. Circadian comes from a combination of the Latin words circa meaning “approximately” and diem meaning “day”, and circadian rhythm is the phrase we use to describe the natural sleep/wake cycle of organisms (including humans) over a twenty-four hour period.

The 24 Hour Clock & Circadian Rhythm

If you thought the twenty-four hour clock was a human invention—think again. Turns out, it’s as natural as sleeping or breathing and has been around for millennia. Our cells run on a twenty-four hour cycle, telling us when to sleep, and when to eat. 

The Greek philosopher Theophrastus first noticed Circadian rhythm in a tree which opened and closed its leaves over the course of a day; the tree would close its leaves every night and begin opening them again in the morning.

As it happens, humans operate quite similarly to Theophrastus’s tree. In 1961, Frenchman Michael Siffre descended into a cave to find out what happens to the human psyche when we live without exposure to the outside world. Planning to stay for two weeks, he ended up spending 25 days in the cave, and proved that humans, like other organisms, have an internal biological clock. 

Although Siffre’s clock was extended slightly (by 30 minutes) when isolated from the day/night cycle of the earth, Siffre ate and slept when his body told him to, and the patterns of his behaviour conformed to a 24 hour period—a circadian rhythm.

How Does Circadian Rhythm Affect My Sleep?

Your circadian rhythm runs in the background without you ever having to think about it, so your body will naturally feel tired at some point over the course of twenty-four hours. But optimizing your sleep schedule to sync with your circadian rhythm can actually improve your sleep and help you feel more rested. You can even adjust your circadian rhythm (for example, in order to go to bed or wake up at different times), but experts say you’ll need to do it incrementally, over time.

While Siffre demonstrated that our circadian rhythm continues to function in the absence of external stimuli, there are some things that have been proven to aid our bodies in keeping our circadian rhythm on track. Natural light, for example, informs our bodies that it’s time to wake up and be active; while darkness can make us feel drowsy.

That’s part of the reason you hear people saying we should put our phones away a few minutes before trying to sleep, and why many people have trouble sleeping in a well-lit room. Nighttime (or the illusion of it) helps our circadian rhythm put us to sleep.

How Does Circadian Rhythm Affect My Workflow?

We all have a most productive time of day—the time of day when we feel most energized to do our work—and this too, has to do with our circadian rhythm. Based on when we go to sleep and when we wake up, we can either feel energized or tired, motivated or unmotivated.

Getting in touch with your circadian rhythm means figuring out your ideal bedtime, sleep length, and wake up time. And once you’ve nailed that down and feel good about the amount of rest you’re getting, you can further determine the times when you feel most motivated to get work done. 

For example, perhaps it takes you some time to “warm up” for your day, so it’s best if emails are handled in the morning, whereas major projects are something you tackle in the afternoon or late at night. 

Your peak productive hours are actually tied to your circadian rhythm, and if you can manage to sync your prime working hours with when your body feels most active, you may start to get more done in the run of a day.

Conclusion

Scientists are still working out exactly how our circadian rhythms work and how they affect us day-to-day, but there’s certainly proof out there that humans run on a 24 hour clock—independent of any alarms, sundials, or wrist watches. Our sleep/wake schedule is important to how we operate as humans, and learning about your own circadian rhythm can help you nail down a healthy sleep schedule and more productive work schedule.