Sleep Cycles: Understanding Your Body’s Natural Rhythm

Homeblogsleep cycles understanding your bodys natural rhythm

Cilliers Marais


You hit the snooze button. Again. How many times has the alarm gone off? Just one more snooze, you tell yourself. And then, when you can’t put it off any longer, you groggily climb out of bed and rush to get ready for the day. Sound familiar? Or maybe you diligently get up at 5 am and accept that being tired is just part of life. But here’s the thing. It doesn’t have to be. Sleep research has shown that sleep cycles play an important role in restorative sleep. And that (restorative sleep) is what we’re all about at Kooi.

Keep reading if you want to feel well-rested and function at your best. In this blog, we’ll explain what sleep cycles are, the various stages your body goes through during a sleep cycle, and why these stages are important.

Earthy bedroom with rust-coloured duvet set, wooden headboard and bedside pedestal with a green plant in a raw clay pot.

What is the Sleep Cycle?

A single sleep cycle consists of four stages of sleep – three stages of Non-Rapid Eye Movement sleep (NREM) followed by a stage of Rapid Eye Movement sleep (REM). On average, you’d go through four to six sleep cycles per night. A single sleep cycle lasts anything from 60 to 120 minutes and the duration of the cycles varies as the night progresses. Moreover, the time you spend in individual sleep stages during consecutive sleep cycles may also vary.

That is quite the mouthful. But don’t worry, in the sections below you’ll learn all you need to know about the four stages comprising a sleep cycle and how they aid your body to recover after a long day.

What are the Stages of a Sleep Cycle

As mentioned the four stages of sleep can be grouped into two main categories: NREM and REM. The first category consists of three sleep stages:

  • Stage 1: N1 or Drowsiness
  • Stage 2: N2 or Light Sleep
  • Stage 3: N3 or Deep Sleep

The second category is made up of only one sleep stage, namely REM sleep.

Stage 1 – Drowsiness

Drowsiness, N1 or Stage 1 are different names for the first stage of sleep. And as the name suggests, it is not actual sleep. Rather, it is the onset of sleep. Moreover, you spend by far the least amount of time in this sleep stage. Quite often, you only experience this stage during your first sleep cycle (if you don’t wake up during the night, that is).

During this phase, your brain activities start to slow down and your body may twitch a couple of times. It is easy to wake someone from this stage of sleep, as they are not fully asleep yet.

Woman lying on a pillow in a light room.

Stage 2 – Light Sleep

Light sleep, N2 or Stage 2 are different names for the second sleep stage. Importantly, your eyes do not move during this stage (hence it falls into the non-REM category). Typically, this stage is shorter during your first sleep cycle and becomes progressively longer as you go through more sleep cycles during the night. You’ll spend roughly 50% of your total sleeping time in N2.

During this stage, your body temperature drops, muscles relax and your heart rate slows down. Light sleep contributes to your feeling well-rested after a night’s sleep and you’ll either transition into Stage 3 sleep or REM sleep after the N2 phase.

Stage 3 – Deep Sleep

Deep sleep, N3 or Stage 3 sleep are all different names to describe the third stage of sleep. It may also be called delta sleep because your brain activity during this period slows down even more and produces brainwaves known as delta waves. You’ll spend most of your time in deep sleep during the first sleep cycles of the night. Moreover, you’ll spend about 20% to 25% of your sleeping time in the N3 sleep phase.

If you think of restorative sleep, you think of N3 sleep. Apart from the deep, slow brain activity, your muscles go into a state of deep relaxation during N3 sleep. You see, it is during deep sleep that your body does most of its healing and recovery. The brain gets flushed out of waste products that built up during the day, increasing brain function the following day. Furthermore, hormones that aid in muscle recovery such as testosterone and growth hormone are released during deep sleep.

It is quite hard to wake someone up when they are in deep sleep. And if you manage to get them awake, they will experience sleep inertia – a state of feeling groggy and disoriented.

Cat sleeping under a white duvet.

Stage 4 – Rapid Eye Movement (REM) Sleep

During REM sleep, your eyes move behind your eyelids. Hence the name. During this phase, your brain activity picks up again, nearing levels of when you are awake. And here’s why:

  • You have vivid dreams during REM sleep.
  • Your brain defragments during REM sleep.

Dreaming is self-explanatory, but what does brain defragmentation look like? Your brain sorts through everything that happened during the day while you are in REM sleep. It stores important and useful information while discarding random information to free up memory space. REM sleep is critical for your continued cognitive function. Without enough REM sleep, you will have difficulty focusing and making critical decisions.

Your body goes into atonia when you are in REM sleep. Basically, it means your muscles, apart from your eyes, lungs, and heart are temporarily paralysed.

On average, you’ll spend about 20% to 25% of your sleeping time in REM sleep. Furthermore, stages of REM sleep increase in length as the night progresses. In the second half of the night, you will often fluctuate between REM sleep and light sleep, with very little to no deep sleep and drowsiness in between.

What Affects Sleep Cycles

Various factors affect your sleep cycle. From how old you are to what you eat. What bed you sleep on, and obviously, your sleeping patterns.

  • Age: Babies and infants sleep more than adults. Moreover, they spend proportionately more time in REM sleep than adults do. Elderly folk spend proportionately less time in REM sleep.
  • Food & Beverage: Caffeine generally has a negative effect on your sleep, if you consume it close to bedtime. Alcohol also reduces the amount of time you spend in REM sleep while it remains in your bloodstream. Once it is worked out, you will either wake up or spend the rest of the night trying to catch up on lost REM sleep.
  • Bed: If you sleep on an old bed or one that is not right for your sleeping style, your sleep cycle will be negatively affected.
  • Sleep Patterns: If you do not have a regular bedtime and wake time, it confuses your internal clock and can affect your sleep cycles.

Can You Track Your Sleep Cycles

Yes you can. Your smartwatch (Apple, Samsung, Garmin, Fitbit, etc.) utilises the heart rate monitor and motion sensors to determine in which stage of sleep you are. Some of the higher end watches have super sensitive motion detection sensors, and so they can fairly accurately measure what stage of sleep you are in, based on heart rate and movement.

Sleep cycles graph as per the Garmin Connect watch interface.
A sleep cycle graph as per the Garmin Connect watch interface.

There are also sleep-tracking apps that you can install on your mobile to track your sleep cycles throughout the night. Like the aptly named, Sleep Cycle app, which tracks your stages of sleep and then wakes you up when it deems you are in light sleep, close to when you normally get up.

Optimise Your Sleep Cycles with Kooi

Head over to the Kooi online store to get your hands on some of the most technologically advanced beds out there. Built to give you the support and comfort you need, it will definitely help you to optimise your sleep cycle.