We all know sleep is important, and most of us probably need more, but do we necessarily know why its so important, and how much we actually need?
Well, here we’ll explain exactly that. The what, why and how of sleep.
So firstly, what is sleep?
Sleep is simply a recurring state of rest which is essential for all bodily functions. From brain function, to immune health, to weight management and anabolic functions for the muscular system.
So yeah, its a big deal and should be one of the first things to address on any program. If you have all those functions working optimally, you’ll undoubtedly see a positive change in your health + physique.
Now lets delve a little deeper into the mechanisms of sleep.
Sleep occurs in cycles of different phases.
Light Sleep (NREM):
So we have 2 cycles of light sleep - non rapid eye movement 1 (NREM 1) - which makes up around 10% - as the name suggests this is a light sleep.
Then, NREM 2 light sleep makes up approximately 50%, for a total of 60% of our total sleep being from light sleep.
Role of sleep in NREM 1-2 phases:
Suppressing cortisol - important as cortisol is a hormone which is responsible for regulating metabolism, blood pressure + blood sugar levels and managing inflammation (usually considered the ‘stress’ hormone).
This phase is a shallow sleep + easy to wake from.
Deep Sleep (NREM):
We then have stages 3-4 which are deep sleep (NREM) - and make up 15% of our sleep time. If we’re getting significantly less, or more then we should look to understand why.
Role + effects of sleep in NREM 3-4 phases:
Majority of repairs occur in bodily tissue (both muscle and all other tissue)
Increase protein synthesis
Increase growth hormone production
Reduced glucose metabolism (perhaps a consideration for late consumption of food).
This is a deep sleep where you’re pretty much KO’d.
Stage 5 is rapid eye movement (REM) sleep which makes up approximately 25% of our sleep time.
Role + effects of sleep in REM phase:
Most muscle paralysis
Helping with memory
Increase in acetylcholine - a neurotransmitter which is important for chemical signalling throughout the body
So how much sleep we do actually need?
Generally we see 90 minute cycles, and 5 cycles per night which should take us to 7-8 hours per night, and 35 cycles per week for adequate or potentially optimal sleep.
We can use a few markers to determine what adequate or optimal sleep actually is:
Hours per night - 7-9hrs
Quality of sleep - consider the 5 cycles - 90 min cycles, % of each (as close to recommended as possible)
Sleep latency (how long it takes to fall asleep) - generally we’d consider the quicker the better as it means your body clock is functioning + there also tends to be a relationship between latency and quality.
Why is this important?
If you track, you can look for ‘optimal’ and see how close you’re getting which will then tell us if all is good, or if we need to intervene and address any issues.
However, even with a bad nights sleep, we have 35 cycles per week, and so 1 bad night is not the end of the world. Instead of stressing, and adding to the problem just take a step back and see if you can identify a problem, and a solution.
So how do we measure that?
We have objective measures such as sleep tracker apps which are not perfect but tend to work relatively well to give us an idea of the duration, quality + latency of our sleep, and allows comparison + re-testing over time.
Other than apps, the only other objective measure we have is a bed time, a wake up time, and the difference between the 2 which allows us to work out how many hours spent in bed.
Next, we have subjective data - you may recall how many times you’ve woken up at night, how many times you went to pee, your sleep satisfaction upon wake (how do you feel?), as well as your energy levels upon wake + during the day compared to other days. Other factors can also affect this however.
You’ve probably heard of the term ‘body clock’ which essentially describes our circadian rhythm which is a 24h biological clock in the human brain.
It’s regulated by something called the hypothalamus which controls and regulates the release of hormones, regulates body temperature, nutrition and appetite, etc.
Our circadian rhythm will generally dictate or have an effect on our bed time, time to fall asleep and quality of our sleep. However, it can be disrupted by a number of factors such as light and dark exposure at different times which is why jet lag can create a whole host of issues with an impact on all of those factors e.g. sleep, appetite, mood, etc.
As a result, we need to understand how we can lay the right habits to promote a regular circadian rhythm and therefore a better quality sleeping environment.