Sleep isn’t as simple as closing your eyes and waking up the next day. You experience five different stages of the sleep cycle a few times throughout the night, with one sleep cycle typically lasting around 90-110 minutes. Each stage serves its own valuable function to make sure you wake feeling rested and refreshed.
How the Sleep Cycle works
This is the lightest stage of sleep; if you wake up while in this stage, you’ll probably feel as though you haven’t slept at all. Your muscles start to relax from the activities of the day, though you may have the occasional twitch every now and again.
Professor Colin Espie, Director of the Sleep Centre at the University of Glasgow and Founder of Sleepio adds that you might even experience a hypnic jerk or sleep start. “It’s a response the body makes to initiate sleep. It’s that transition just between wakefulness and sleep when you just fall over and you’re awake again.” He further adds that 70 per cent of people have sleep starts, so it’s not something to worry about!
Not only that, but your eye movement and breathing starts to slow and your brain emits what is called alpha and theta waves. It’s a very short stage, only lasting around seven minutes.
In this stage of the sleep cycle, you’re still in a light sleep. Professor Espie explains that 50% of our night is actually spent in this stage. However, you’re well on your way to falling into a deep one, with your heart and breathing slowing down even more. Your body temperature and brainwave activity decrease. Your body prepares to enter into the deep sleep you want.
If you were to have a power nap, this is the stage when you’ll want to wake up. Anything after this, and you’ll feel very tired and groggy. In this stage, however, a quick nap can really help you feel refreshed.
Deep sleep finally occurs in stage three of the sleep cycle. This is what you need to experience to feel refreshed and revived the next day. Brainwaves called delta waves are emitted by the brain. Your muscle activity stops as does your eye movement. Once you hit this stage of the sleep cycle, you’ll find it hard to wake up.
You’ll further progress into a deeper sleep in stage four. This is the restorative stage of sleep, and why so many people preach about how sleep is so important for your health. Your body starts to repair your muscles and tissues, especially important if you’ve been exercising. This is also why you’ll find it hard to recover if you haven’t had a good night's sleep. As well as regrowing tissue, you’ll also build your bone strength and immune system.
You’ll probably be able to sleep through any loud noises or disturbances throughout the night. But if you do wake up during this stage, you’ll feel lost and disoriented for a few minutes.
And now, we’ve finally moved from non-REM sleep to REM sleep, approximately 90-minutes after you’ve gone to bed. Your first REM cycle will last around 10 minutes and takes up approximately 20-25 per cent of the night. Then as you go through your subsequent REM cycle throughout the night, they’ll gradually last longer. Your final one can last up to an hour.
The REM cycle is where most of your dreams occur because this is when your brain is most active. Your eyes twitch back and forth, your breathing quickens and becomes shallow, and your heart rate increases. However, while your brain activity looks similar to how it functions when you’re awake, your muscles are paralyzed and you won’t be able to move.
It’s important to reach this stage because this is when your brain gets to work. REM helps with your learning and processing the information from your day. It also assists in your long-term memory.
It’s really important to get enough sleep so that we can function and perform our best the next day, not to mention, just to feel good and energised. On a final note, Professor Espie says, “the brain is a pretty powerful organ and it needs its sleep to function.” We need to experience all the five stages as they each serve their own purpose. So set yourself a bedtime and stick to it. You’ll thank yourself for it!