Your internal clock clock explained (circadian rhythm)

You have probably heard about ‘your internal clock’ – but what does that actually mean?

Well, this is closely linked to what we call circadian rhythms. These are physical, mental and behavioral changes that follow a 24-hour cycle. They affect most of living things (including animals, plants and even microbes).

In humans, these rhythms coordinate mental and physical systems and they’re tied to a ‘circadian pacemaker’ located in the suprachiasmatic nucleus (let’s call it SCN) within our brain, which will regulate activity throughout the body by sending different signals during different times. The SCN is very sensitive to light, which is why circadian rhythms are closely connected to day and night. But other factors such as exercise, social activity and temperature also affect your internal master clock.

One of the most important and well-known circadian rhythms is the sleep-wake cycle. In general, your SCN sends signals throughout your body during the day that help us stay awake and active. As the night comes around, the SCN starts melatonin production, a hormone that promotes sleepiness and then keeps transmitting signals that help us stay asleep throughout the night. This way, the sleep-wake rhythm creates a cycle of restorative sleep to enable a sustained increase in daytime activity.

When this circadian rhythm is thrown off, the body’s systems don’t function optimally. Without the proper signaling from the body’s internal clock, we can struggle to fall asleep, wake-up during the night or experience shallower, fragmented and lower-quality sleep. All of this can leave you feeling low-energy or lethargic during the day.

So how do you maintain a healthy circadian rhythm? Some actionable tips to optimally ‘set’ your internal clock:

1. Exposure to natural light (especially early in the day): the SCN is heavily influenced by light. Hence this is a strong cue for wakefulness.
2. Limit light before bed: same logic as 1., but the other way around. Dim those lights and limit blue light intake for a strong cue for sleep.
3. Have a set nighttime routine and consistent sleep schedule: having an enjoyable nighttime routine is one of the strongest ways to hack your SCN to signal to your body it’s time for rest. Add physical cues for extra effectiveness. Consistency is key.
4. Get daily exercise: this can support your internal clock and hence help you fall asleep at night. And hey, is there anything not beneficial about some exercise?
5. If you need them, keep naps short and early in the afternoon: late and long naps can push back your bedtime and throw your sleep schedule out of whack.
6. Maintain good sleep hygiene: a catch-all tip (see our earlier post to explore the concept of sleep hygiene.

Have a look at when your body does what in the circadian rhythm: