“Sleep is this tremendously important period of our life because it resets our ability to be focused, alert and emotionally stable in our wakeful periods”
– Prof. Andrew Huberman
Our wakeful periods and sleep periods are tethered to each other and what we do in our wakeful periods determine how and when we get to sleep, how quickly we get to sleep, whether we stay asleep and how we feel when we wake up the next day.
Sleep hunger
The first factor to consider regarding your alertness or sleepiness levels is adenosine. Adenosine is a molecule in our nervous system and body that builds up the longer we are awake. So, if you have had a great sleep for say 8, 9 or 10-hours, adenosine is going to be low in your brain and body. Adenosine, and the increase thereof, creates a sleep hunger. As a brief side note here on caffeine, caffeine operates in a way that it blocks the adenosine receptors in the body, thereby not allowing this molecule to build up.
There is a second force which determines your levels of alertness and sleepiness. This force is your circadian rhythm. We all have an internal clock that determines when we want to be asleep and when we want to be awake. And what helps set our circadian rhythm is light, and in particular sunlight. The relationship between light and when you want to sleep is fundamentally important and a high value needs to be placed on this relationship.
When you wake up in the morning a small pulse of the hormone cortisol and epinephrin is released and makes you feel awake and alerts your systems in the body to begin moving. It is important that this pulse of hormones comes early in your day. And what is important about this is that it sets an internal timer in your body to release a different hormone called melatonin (which makes you sleepy) later in the day. This internal timer usually goes off between 12-14 hours later and then melatonin gets released. So, there are 2 systems in play here, a wakefulness signal and a sleepiness signal. And the wakefulness signal triggers the onset of the timer for the sleepiness signal. Simply put:
- Cortisol for alert and wakefulness (ideally early in the morning)
- Melatonin for sleepiness (ideally 12-14 hours later)
When you wake up and light comes into your eyes, it sends an electrical signal to our internal clock (the suprachiasmatic nucleus), and this then stimulates the timing of cortisol release as well as activates the timer for the release of melatonin 12-14 hours later. Multiple studies now show that if you do not get your cortisol and melatonin rhythms right there are tremendously bad effects on cardiovascular health, dementia, metabolism, focus, learning, depression, plus many other negative health risks.
The importance of light
We need enough quality and amount of light (and not just any light) to trigger our internal clock for the release of the cortisol and melatonin rhythms. And this quality and amount of light comes directly from sunlight. In the morning, these cells in the eye require low solar angle sunlight to be activated. You want to try and get sunlight in your eyes as close to waking as possible. Sunlight in the morning triggers the activation of these cells in the eyes. Be sure to get outside to view the sunlight as it’s 50 times less effective to view this sunlight through a window. Getting your cortisol pulse early in the day (and further away from your melatonin pulse) has huge health benefits so be sure to try and get into a regular pattern of this in the mornings. This can be anywhere from 5-15mins in the mornings depending on the amount of sunlight available to you. Even if cloudy and overcast there are significantly more light particles in the air as compared to a well-lit room. Be sure NOT to look directly into the sun and hurt or damage your retinas.
A brief side note here, blue light (as you would get from looking at screens) is not the enemy at this early part of your day when you are trying to set your circadian clocks. It has been shown that it can assist the release of cortisol and subsequently set the timers for the melatonin release 12-14 hours later. You want to avoid as much blue later in the day especially in the 2-3 hours before you want to go to sleep. Light suppresses melatonin. But do not be fooled that waking up and just looking at your phone will release the cortisol pulse, it will not. Getting outside for 5-15mins of sunlight will.
In order to set and anchor your internal clock you will also need to try and view sunlight also in the late afternoon/evening i.e. low solar angle. The cells in your eyes (melanopsin cells) signal the central circadian clock that it is getting toward the end of the day. Having these two signals (morning and evening light) sent to your internal clock is tremendously powerful.
Encouragingly, it generally only takes around 2-3 days for these systems to align, and you know you will be getting it right when you begin to wake up roughly at the same time each day and start to feel sleepy and go to bed at roughly the same time also.
The bad effects of light
“Light is not supposed to arrive in our system at any time”
– Prof. Andrew Huberman
Because we now have unlimited access to artificial light from screens and within our home, light can be received at times of the evening we normally wouldn’t want to access light. The longer you have been awake the more sensitive the cells in your retina are to light. Therefore, even a small amount of artificial light later in the evening can trigger our internal clock and give our brain and body the signal that we want to stay awake longer. You want to get less light after the hours of 8pm and you want to avoid at all costs bright artificial light between the hours of 11pm and 4am.
Studies back this up as light that arrives to the eyes between 11pm and 4am suppresses the release of dopamine (the feel-good hormone), inhibits learning, affects mood, affects metabolism, decreases focus, increases anxiety, and creates all sorts of other detrimental health effects. But seeing this light between 11pm and 4am also goes on to activate a part of the brain (the habenula, which is called the ‘disappointment nucleus’) which makes us feel less happy, more disappointed and can lead to certain forms of depression in the wakeful state.
Besides light, the timing of food intake as well as exercise can also help set your circadian rhythm, but light intake is the keystone behaviour and protocol over a consistent period that determines your healthy sleep-wake rhythms.
Sleep for learning
Experts have discovered sleep is important for learning and memory in 4 ways:
1. You need sleep before learning to get your brain ready to make new memories
2. You need sleep after learning to ‘hit the save button’ on those new memories
3. Sleep, and including dream sleep, will intelligently interconnect those new memories together AND it will also connect them with your past back catalogue meaning that problems you may have been wrestling with for some time now become clearer and solvable
4. Sleep helps you forget, and this is essential. You don’t want to remember everything and store every piece of knowledge as this will overlap and become muddled. Sleep will not universally strengthen every piece of information, sleep will selectively enhance those things it deems important for learning
Multiple studies point to the benefit of what academics now call “delayed offline learning” and it comes across exclusively in sleep. During the delayed offline learning the conscious efforts that took place in the day, or over several days, begin to percolate into the subconscious mind. What the studies also go on to show is that when delayed offline learning took place, participants performing cognitive or motor tasks were more fluid, more seamless, lacking errors and overall, more autonomous than the control group by a percentage of between 25-40%. They were essentially calling on the subconscious mind to do some of the heavy lifting. Whereas the participants who did not gain delayed offline learning were chunking the information, having multiple mini stops and pauses and were conscious in the task they were in and using a lot of willpower and effort.
Sleep was able to identify where the difficulties lay in a cognitive tasks or motor skill execution and was then able to smooth them out. So, the next day, participants were able to perform their tasks with a lot less willpower and mental effort being used.
With FMRI scans and brain mapping technology, we are now able to see and understand what is happening in the brain during sleep and how delayed offline learning works. In simple terms, what is happening is that sleep transfers the memories to the brain circuits that operate below the level of consciousness. And as a result, these skills now became instinctual habits with very little willpower or effort being used to execute. A nice analogy to bring this to life is like we are receiving a USB device with the days learning and memories on it, this is not permanent memory, but then when we sleep, it is like we are plugging that USB into our main computer and downloading all that information into a bigger and more permanent hard drive. Therefore, taking vulnerable short-term learning to a more permanent long-term storage site. In the brain, this is transferring the memories from the hippocampus (short term) to the cortex (long term).
Mental health
“The best bridge between despair and hope is a good night of sleep”
– E Joseph Cossman
Matthew Walker and his colleagues have a large series of different research programs looking at the links between sleep and mental health that have taken place over the past 20-years. What Matthew says is that “we have not been able to discover a single psychiatric condition in which sleep is normal”. That tells us so much about the close relationship between your sleep health and your mental health. We now know that sleep impacts the circuits of your emotional brain (the amygdala). Without sleep the emotional brain becomes hyperactive and irrational. Studies have shown that the amygdala of people who experienced a lack of sleep was 60% more reactive compared to a control group.
“A ruffled mind makes for a restless pillow”
– Emily Brontë
The reason the amygdala, our emotional part of our brain, gets affected in this way is that the pre-frontal cortex (which helps regulate our deep emotional impulses) gets taken offline when we are not getting sufficient sleep and the connection between these two parts of the brain is eroded. Consequently, we become all emotional gas pedal and too little regulatory control brake pedal. That same neurological profile caused by a lack of sleep is observed in people who have depression and anxiety disorders including things like PTSD and phobia disorders. This is a 2-way street, as bad sleep can cause these disorders and subsequently, people are not able to sleep effectively due to these disorders. But the studies show that it’s the lack of sleep initially that heightens the surface area for these disorders to appear.
With a sleep intervention, sleep provides emotional first aid and acts almost like a nocturnal soothing balm. It will take those difficult emotional experiences we have had in the day and take the sting out of those memories. Sleep helps to divorce the emotion from the memory. It’s not as though you have forgotten the emotional experience, but the recollection of that emotional memory no longer comes with the same degree of emotional reaction you had at the time. So, in other words you go to sleep with an emotional memory, but you wake up with a memory of an emotional event. It’s not time that heals all wounds, but time during sleep that provided that emotional regulation and rationality.
“Sleep will provide, in essence, a sense of overnight therapy”
– Matthew Walker
Match preparation
How can this transfer into squash and life? I often get asked what the best thing is I can do to prepare for a match or event coming up. My biggest piece of advice would be to ensure you prioritise sleep. Yes, you need to sharpen up with some drills and match play, yes you need to eat well and get your stretching in, yes you need to mentally prepare and visualise. But sleep is the gateway and keystone habit to getting all the other factors correct. If you have a bad sleep routine then you will be waking up mentally blunt, your body will be craving sugary foods, you will likely make bad choices about what to choose to eat, your training will then be affected as your body is now not in an optimum state to perform. When at training you will have brain fog and not be able to process information quickly as well as store it. Your mood will likely be negatively affected due to the bad nutrition and subsequent training. The knock-on effects of having bad sleep on a regular basis can be highly detrimental.
Sleep has been given so much attention of late about its importance and relevance, that the International Olympic Committee in 2015 published a consensus statement highlighting “the critical importance and the essential need for sleep in athletic development across all sports for men and women”.
Studies have now identified that the improvements of speed and accuracy of a motor skill happens in Stage-2 NREM sleep, which specifically occurs in the last 2-hours of an 8-hour sleep cycle. So don’t wake up too early! Don’t cut the sleep short! It is tempting to think waking up earlier to get in extra sessions or train harder is beneficial (and it is in the right context). But realise that when you are cutting into your final 2-hours of sleep before waking you are not letting yourself deep learn what has come before. Your ability to absorb and retain the motor skills gets negatively affected.
“Practice does not make perfect; it is practice followed by a night of sleep that leads to perfection”
– Matthew Walker.
A good analogy for how sleep can be effective is by using a masseur. A good masseur will give you an all-over body massage but will hone in and specifically target the key areas that need the most work and attention. So, in the same way a good quality night of sleep bathes all parts of the brain, more emphasis is placed on those parts of the brain that have worked the hardest and been stretched during the day. Like what the masseur would do with your body that has tightness in say the hamstrings due to repeated ghosting or a particularly hard match. They would not just purely focus on one area but spend a good portion of time working out the knots and tightness in the hamstring so you can perform optimally the next day. Quality and consistent sleep does this, it is like having your own built in personal masseur for your brain.
Tools to help you sleep better
- Viewing light early in the day, ideally sunlight, is key for establishing healthy sleep-wake rhythms and for allowing you to fall asleep easily at night
- Be consistent in your morning sunlight, link this to a habit of going out for a brief walk which has other health benefits also
- Get as much light as you can earlier in the day and reduce the amount of light you receive later in the evenings
- Work on attaining a streak of good sleep habits and prioritize this above all else. See if you can start with 1-week of high-quality light each morning for 10mins and see how you feel
- Keep a sleep journal next to your bed noting the time you woke up and a score out of 10 for the quality of sleep. Look back at this after several weeks to see a pattern that may be developing
- Further resources on sleep: Matthew Walker Why We Sleep, The Huberman Lab podcast, Dr. Guy Meadows