Sleep and your circadian rythm


You have probably heard many times about the need to tune-in with your circadian rythm. For many people this may seems exotic and theoretical. But it far from that! Every living being has it’s own circadian rythm based upon our body performs its daily functions with a specific, choreographed routine – our circadian rhythm.

Circadian refers to our body’s 24-hour cycle based on the pattern of the sun. This is a series of physical and chemical changes that occur every single day and are genetically hardwired. They influence our energy levels, hunger, and alertness. We may not realize it, but when our lifestyle aligns with our body’s natural rhythm it is the time when we also feel at our best.

Our internal clocks

Circadian rythm –

Everyone has feedback systems that consist of “time keepers” which get activated by certain environmental cues. Cues can originate from your environment (e.g., sunlight) or body (e.g., food entering the stomach). These cues promote sleeping (a relaxing state) or staying awake ( a stress state). These internal clocks react to all the external cues and communicate with one another throughout the day exchanging messages. This is controlled in a tiny region of the brain in the hypothalamus, called suprachiasmatic nucleus or nuclei (SCN). It is responsible for controlling circadian rhythms. The neuronal and hormonal activities it generates regulate many different body functions in a 24-hour cycle.

For example, if there’s light, a message will be sent “it’s daytime, let’s get to work!” to alert all of your internal clocks. If it’s dark, it will deliver a message “it’s night time, let’s power down!”. If on the other hand, we just had a large meal, the stomach will send a message to the SCN and other clocks to say “Sorry, everyone. I’ve got a lot of work to do, we can’t shut down just yet.”

Sleep cycle

When we are aligned with our circadian rythm, and our body recieved the right signals at the right time we should get a good night sleep. This is reflected into key markers, the Resting Heart Rate (RHR) and Body Temperature. But all the signals need to be there, in order to align the various internal clocks.

Your RHR should be at its lowest point in the middle of your sleep (2-3am). However, if for example you are browsing the social media your phone’s blue light will get mis-interpreted as daylight and there will be messages sent around saying “it’s daytime, let’s get to work!”. Your heart then receives this message and speeds up even if you’re lying in bed and trying to wind down before sleep!

Similarly, if you did a cardio workout late in the night, your body temperature will be high and the signals sent around will delay your body to power down. That is why, a lower room temperature (around 18-19 °C ) is always a good cue to the body to start dialling down.

To find out what is your own circadian rythm look for simple signs such as

  • Falling asleep in a short period of time (5-10 min).
  • Waking up feeling well-rested after an 8-hour sleep. Ideally you should wake without an alarm clock. Give this a try!

Key takeaways

  • Sleep is critical for health, growth, longevity. Respect your circadian rythm.
  • Everything we do, results into cues to our body to relax or stay active.
  • Resting Heart Rate and Body Temperature are the best mertices for predicting a good night sleep. Buying a good sleep tracking device will help a lot.
  • Try putting your alarm clock away for week, to tune-in with your circadian rythm.

Further Reading

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