Proper, healthy sleep is critical in our body’s ability to recover from the daily challenges we put it through, whether that’s from our workouts or just our everyday lives.
Sleep is also the first thing we as humans ignore to focus on! Yet time and time again, we hear that we need to prioritize sleep to achieve optimal health…
The odds of being sleep deprived (less than 6 hours a night for adults) has increased significantly over the past 30 years as the lines between work and home have become blurred and digital technology has firmly become part of our lifestyles. Poor sleep health is a very common problem with 25 percent of U.S. adults reporting insufficient sleep or rest at least 15 out of every 30 days. The National Institutes of Health predicts that America’s sleep debt is on the rise and that by the middle of the 21st century more than 100 million Americans will have difficulty falling asleep. (1)
This is not only bad from a health perspective, but from many other aspects. For example, drowsy driving may be a factor in 20% of all serious motor vehicle crash injuries!
Another example is the enormous impact on our economy, as sleep deprivation and untreated sleep disorders are estimated to cost over $100 billion annually in lost productivity, medical expenses, sick leave, property, and environmental damage. (2)
Not to speak of the many mistakes that are made at work places regularly due to sleep deprivation, for instance doctors amputating wrong limbs or surgeons making fatal errors.
Before you think this guide is not for you, because you do just fine on 5 hours per night. Let me just say that the chances are very slim that you are one of the individuals with the rare genetics that are not affected by sleep deprivation. Sleep researcher Matthew Walker says “No aspect of our biology is left unscathed by sleep deprivation (…) In case you’re wondering, the number of people who can survive on five hours of sleep or less without any impairment, expressed as a percent of the population and rounded to a whole number, is zero.” (3)
But it not only the duration of the sleep that counts, but also the quality that needs to be addressed.
Non-REM sleep, (also known as deep sleep or slow wave sleep) is most related to recovery for your body, while REM sleep is vital for recovering your brain. However, the daily life stressors, the challenges we face, the stimulus of electronic devices and our surroundings can keep our brain and body from reaping the benefits they deserve from quality sleep.
But don’t worry, here is your ultimate guide to increasing the time and quality of your slumber so that you can not only improve your performance, aesthetics, energy throughout the day, mental health…but also live longer and maintain cognitive health as you age. (4)
We will cover
→ Why we even need to sleep (and the stages of sleep)
→ Short term consequences of sleep deprivation
→ Long term consequences of sleep deprivation
→ Recommendations and tips for sleep (the stuff that you are actually here for 🙂 in regard to
→ Training
→ Nutrition
→ Supplements
→ Lifestyle
→ Specific guidelines for sleep
→ FAQ
Why we even need to sleep (and the stages of sleep)
The main reason why we get to a point where we can’t hold our eyes open anymore and why we are even able to sleep can all be connected to a single neurotransmitter in the body, Adenosine. Adenosine is a ‘messenger’ in our brain that accumulates throughout the day and it is that buildup that causes you to feel tired as the day progresses on. It is adenosine’s main role to signal to the body that energy reserves are low and that the body is in need of sleep so that it can build back up its energy stores. Therefore, in order for you to have optimal energy levels, your body and mind has to physically sleep and sleep well. (5)
Throughout the night we go through various stages of sleep. Each one of them has a purpose and is important in its own way.
REM sleep is a stage in which the brain is active but the body is paralyzed. REM, stands for “restless eye movement” and comes from the fact that during REM sleep our eyes dart about underneath our eyelids. It’s during REM sleep that we have our most vivid dreams.
Non-REM sleep is a stage in which the brain is relatively inactive and our body is movable. Non-REM is further divided into stages based roughly on how deep the sleep is and how difficult it is to wake someone up from it.
There are 5 stages of sleep. According to the American Association for Sleep Medicine (AASM) classification, there are 5 stages of sleep:
→ Stage W: Wakefulness
→ Stage N1: Relaxed Wakefulness
→ Stage N2: Light Sleep
→ Stage N3: Deep Sleep, or Slow-Wave Sleep (SWS)
→ Stage R: REM Sleep: Dreaming
Stage N1
Stage N1 Sleep is a transition stage between wakefulness and the deeper stages of sleep. It is easy to wake up from this stage. During N1 you are aware of your surroundings but you become increasingly relaxed as you drift off to sleep.
During the first sleep cycle, you usually spend less than 10 minutes in Stage N1 sleep. It accounts for approximately 5% of total sleep time.
Physiology: Core body temperature drops at sleep onset, slow eye movements, lack of sleep spindles in the EEG
Experiences: Hypnic jerks, illogical thoughts when drifting off to sleep, reduced awareness of surroundings
Function of N1 Sleep: Transition from wakefulness to the deeper stages of sleep
Stage N2
Stage N2 sleep is stage of light, regenerating sleep. It is still relatively easy to wake up from this stage of sleep. As you fall asleep, the muscles in your upper airway relax and make your airways narrower, causing you to start breathing heavily. N2 stage sleep makes up the majority of our sleep: 45–50% in healthy young adults. With 8 hours of sleep, that is 3.5–4 hours of N2 stage sleep per night.
Physiology: decreased heart rate, decreased blood pressure, no eye movements
Experiences: fragmented dreams, brief arousals from sleep
Function of N2 Sleep: rest and recuperation
Stage N3
Stage N3 sleep, deep sleep or slow-wave sleep (SWS) is the most rejuvenating and restorative sleep stage. During deep sleep, the glymphatic system removes waste, like neurotoxins and beta-amyloids, from the brain.
There are several ways to get more deep sleep, from establishing good sleep hygiene to taking hot showers before bed, but more later on. But keep in mind that all stages of sleep are important for health and good-quality sleep, not only deep sleep.
Physiology: EEG shows slow-wave brainwaves, decreased heart rate, decreased blood pressure, release of growth hormone, no eye movements
Experiences: very difficult to wake up from deep sleep, if awoken, disorientation and grogginess
Functions of N3 sleep: cell repair and rejuvenation, replenishing glycogen, long-term memory, removal of waste from the brain: glymphatic system
Stage R
REM sleep is a sleep stage in which the brain is active, but the body is paralyzed. Vivid dreams happen during REM sleep and your heart rate and respiration rate are increased. In terms of brain activity, REM sleep resembles wakefulness.
You tend to get more REM sleep later in the night. REM sleep may be completely absent from the first sleep cycles of the night.
REM sleep is linked to the circadian rhythm of our body temperature: our core body temperature starts to drop off when we fall asleep and reaches a nadir in the early morning hours. If you go to bed much later than usual, you may skip the first cycles of sleep (including regenerative deep sleep stages) and even go straight to REM sleep.
Physiology: rapid eye movements, loss of muscle tone, low amplitude mixed frequency EEG, limited thermoregulation, shivering or sweating, elevated heart rate, elevated respiration rate
Experiences: vivid dreams, erections and blood flow to the genitals
Functions of REM sleep: learning and problem solving, memory consolidation, mental health (6)
I won’t go into the many benefits of sleep, because – let’s face it – there is basically no physiological or mental process that does NOT benefit from sleep.
Want to enhance your performance and recovery? – prioritize sleep.
Want to remember more and have more energy for your job? – prioritize sleep.
Want to live longer, healthier and have a more positive outlook on life? – prioritize sleep.
You get it and I think we all know that we should probably sleep more.
Repercussions of Sleep Deprivation
Short term (from as little as one night onwards)
→ Even one night of sleep of 4 to 6 hours can negatively affect our cognition and problem-solving abilities.
→ Even the modest effects of sleep loss have been clearly shown to have a negative effect on a person’s hunger and satiety hormones, leptin and ghrelin
→ Reducing insulin sensitivity and glucose tolerance, which will also hinder your fat loss goals by not allowing you to handle the carbohydrates you are taking in.
→ Noticeable impact on the amount of testosterone that a male produces as well as being connected to lower libido and infertility levels.
→ 75 percent of a person’s Human Growth Hormone (HGH), a hormone that is particularly important for growth and repair of the body’s tissues gets released during sleep with the major period of that HGH release occurring during the first period of deep sleep.
→ Raised cortisol, which is also linked to fat gain or to hindering fat loss. Cortisol is the hormone that helps you wake up in the morning, this is when its high, and it drops at night which helps you get to sleep. If you’re not getting enough sleep then you will have raised cortisol levels for a longer period of time. E.g. if you get 4 hours of sleep instead of 8 it means you have about 4 extra hours of raised cortisol levels during the awake state and the more sleep you miss throughout the week the more cortisol will build up. Soon you will have higher cortisol levels all day which will produce more stress, less sleep and ultimately less fat loss.
→ In addition to these hormones mentioned, the quantity and quality of sleep also has a huge impact on several different hormones in the body, a few of which you may not know much about, but they all have a big impact on the dieting process such as ADH or Antidiuretic Hormone – it is ADH that tells the kidneys to not release as much water, reducing your need to go to use the toilet during the night or in general make all of those trips to the bathroom. Prolactin – as it is primarily known for promoting the creation of breast milk production in women, however, most do not know that it also plays a role in 300 separate functions in the body, with two of the biggest being immune system regulation and metabolic rate…
Long term:
→ Can worsen numerous chronic and degenerative diseases with just a few of them being cardiovascular disease, ulcers hypothyroidism, autoimmune conditions, depression, anxiety, Alzheimers and mood disorders.
→ Accelerates the aging process (higher oxidative stress and less toxins are being cleared out of the body.
→ Disrupted circadian rhythm (for example through shift work or prolonged periods of sleep deprivation).
→ This interrupts the production of many of their important neurotransmitters in the brain. As, it is through many of those same neurotransmitters that regulate a person’s mood, level of depression and or anxiety, cognitive performance, and of course, their super important energy levels.
→ It also disrupts cell autophagy (which is one of the main reasons that chronic insomnia leads to 3 times the risk of dying of ANY cause). During the regular course of the day, the cells in the body have to produce energy so the body can function and as a by-product of that energy creation process, that oxidative stress develops and it can contribute to the damage of cell parts which can render parts of those cells dysfunctional. If a person’s circadian rhythm is being chronically disrupted, then all of that healthy recycling that should be taking place during sleep, gets disrupted.
→ The sleep that someone loses they can never get back and the consequences from sleep that is lost from one single night is much different from the consequences from persistent lack of sleep night in and night out.
General Recommendations for Sleep
An optimized circadian rhythm is the ground work that needs to be laid before anyone can have a high level of sleep efficiency. The reason why, is that the circadian rhythm controls the depth and the quality of your sleep, and it directly modulates a person’s health wakefulness, stress, appetite and energy hormones, neurotransmitters and their longevity. The human body is tied to the rise and fall of the sun. Meaning that every person 24-hour natural clock in their brain that controls all sorts of things based on 24-hour cycles of (natural) light and darkness. The human body has evolved to run on sunlight and when you take it away for longer periods of time or neglect to pay attention to the sun, it can throw a huge curve ball into a person’s quest for good quality and efficient sleep.
Training:
→ Don’t train too close to bed time, in order to avoid a cortisol spike right before you try to wind down. You might find yourself unable to go to sleep.
→ Keep your training volume at a level where it is effective for your goals, but also where your cortisol levels are not going to be chronically elevated, otherwise you might find yourself waking up multiple times per night or getting up to pee too frequently (this can be a sign of over training or training at an intensity too high)
→ If you cut your sleep short (less than 6-7 hrs) in order to get up and train you might shoot yourself in the foot and actually achieve the opposite of what you are trying to do. As mentioned, sufficient sleep is probably the most underrated performance enhancing ‘drug’ there is and can contribute massively to muscle growth, recovery and performance.
Nutrition:
→ Calorie consumption: Eating ‘enough’ food over the course of the day is one of the best things you can do to help with sleep (this does not mean you should stuff yourself before going to bed). If we are in a caloric deficit, sleep is almost always going to suffer eventually. This is one of the reasons why it is important to monitor biofeedback and take diet breaks throughout a cut (so to periodize your nutrition)
→ Don’t eat too close to bed time (larger meals at least 2-3 hours before bed, smaller meals at least 60 minutes before bed). Don’t consume too many fluids close to bed time either, in order to avoid having to go to the bathroom throughout the night. But also make sure not to go to bed too hungry as mentioned above.
→ Meal composition: Carbs can help us relax and can therefore be beneficial for sleep, however make sure to stay away from sugary foods or highly processed foods as they can cause insulin spikes throughout the night and cause you to wake up. Ideally your pre-bed meal should also contain someprotein to help with muscle protein synthesis throughout the night
→ Caffeine: It is wise to cut off caffeine consumption about 10 hours before going to bed. This might seem excessive, but in some people caffeine has shown to take that long to be cleared out of the body. Caffeine basically works by blocking the adenosine receptors for some period of time. If these are blocked it is hard for melatonin to be produced and therefore our sleep to be initiated.
→ Alcohol: It is often believed that alcohol helps us go to sleep. Alcohol helps us relax and induce sleep, yes, but when consuming alcohol we almost always remain in lighter sleep stages, causing us not to recover in the same way. Regular alcohol consumption is therefore advised to be kept to 1-2 nights per week as opposed to having your daily “night cap”.
→ Sleeping pills: sleeping pills are basically a “band aid” that might offer a short-term help, but not an actual solution since they don’t address the problem (cortisol, circadian rhythm etc). We may drift off to sleep quicker, however, similar to under the influence of alcohol, we do not get as restful of a sleep as we naturally would.
Supplements:
I am no one to acclaim that supplementation will fix your sleeping issues, but for the inclusiveness of this guide, I am going to provide a fairly in-depth list of natural sleep supplements that might help with your sleep issues (given the basics, such as nutrition/training/lifestyle recommendations, are covered).
Helpful for people who tend to have an active mind at night:
→ Magnesium: acts as a critical electrolyte that helps with body temperature regulation, allowing it to log more sleep time. Other research shows that magnesium increases the neurotransmitter GABA in the brain, which is responsible for calming your mind and helping you fall asleep.
→ Calcium: helps your brain manufacture the sleep-inducing substance melatonin. Melatonin then helps your body lower its core temperature. If your calcium levels are low, you are likely to experience disturbed sleep patterns, particularly in the REM sleep phase.
→ Omega 3: form the building blocks for a vast number of compounds involved in regulating body temperature, among other critical body processes. Also, the DHA that your body synthesizes from your intake of omega fatty acids stimulates melatonin – a critical hormone that supports sleep.
→ Valerian Root Extract: contains a variety of natural chemical compounds that support sleep and may reduce anxiety, including Valerenic acid and Isovaleric acid. Valerenic acid helps to prevent the breakdown of GABA, a neurotransmitter that helps calm your nervous system, and thereby supports more restful high-quality sleep, and lowers anxiety levels. Isovaleric acid helps your body produce melatonin, known as the “sleep hormone,” that tells your body when it’s dark outside to prepare it for sleep).
→ Lemon Balm Extract: contains chemicals called terpenes and eugenol. Terpenes play a role in the herb’s relaxing effects. Eugenol helps to calm muscle spasms and numbs tissues. Various studies show that the combination of lemon balm combined with other calming herbs (such as valerian) helps to reduce anxiety and promote sleep. Another study showed that lemon balm on its own increased mood and significantly increased calmness and alertness.
→ Magnolia Bark: contains various bioactive compounds, including honokiol and magnolol, which give it anxiolytic properties, helping to reduce anxiety and stress, indirectly promoting sleep. The bark can also act as a sedative, more directly facilitating sleep. It also boosts GABA, a calming neurotransmitter in the brain, helping to reduce anxiety further and promote sleep. May lower levels of the adrenaline (which is alertness-inducing), making it an effective natural sleep aid for people with higher levels of stress. Research shows at least one bioactive compound in magnolia bark can increase the amount of time you spend in both REM sleep and NREM sleep and reduce the time it takes you to fall asleep.
→ Jujube Fruit Extract: contains the phytochemicals saponins and flavonoids, which can trigger changes to neurotransmitters, including GABA and serotonin, which calm the mind and quiet neural activity, making it easier to fall asleep and stay asleep. And jujube contains a specific flavonoid compound called spinosin, which appears to trigger sleepiness through its effects on serotonins. Research suggests that one of the flavonoids in jujube can increase time spent in slow-wave sleep (NREM-3) and REM sleep, the two most restorative stages of sleep.
→ Glycine (can help you fall and stay asleep by lowering your core body temperature. It also may have a calming effect on your brain. Studies show that a glycine-induced lowering of core body temperature supports non-rapid eye movement (REM) sleep NREM sleep.)
→ The nutrients L-theanine, L-ornithine, L-arginine, vitamin B6 and potassium help you achieve deep, lasting, relaxing sleep, so you can wake up refreshed and ready to execute tasks all day long – instead of feeling sluggish with brain fog.
→ Helpful to achieve REM sleep.
» Melatonin (a hormone produced in the pineal gland to signal the body when it becomes dark outside, telling the body it’s time to sleep. The production of melatonin decreases with age, with a sharp yearly decline after age 30, which likely contributes to increased sleep difficulty with age, as well as to overall susceptibility to disease. Several studies show that melatonin may increase REM sleep.)
» GABA (produced by neurons in the brain, which helps control REM sleep timing. Low GABA levels can disrupt or even prevent REM sleep. Evidence shows that the combination of GABA and glycine support REM sleep by “switching off” the specialized cells in the brain that allow muscles to be active, paralyzing the body temporarily, which is required for REM sleep.) You can find a great product which combines GABA, melatonin and magnesium here.
» 5HTP (an amino acid your body produces as a precursor to serotonin. Low serotonin levels are associated with sleep disorders, among other conditions like depression and anxiety. Studies with 5HTP have shown promise with sleep disorders and insomnia, especially increasing REM sleep.)
» L-Tryptophan (our bodies convert L-tryptophan to 5HTP. By helping the body maintain its 5HTP levels, supplementation with L-tryptophan acts as a time-released 5HTP. In this way, it supports REM sleep indirectly.)
Lifestyle:
Try to manage your stress as best as you can. As mentioned earlier, chronic stress leads to chronically increased cortisol levels and can be one of the main causes for mental health issues and sleeping disorders.
→ Include more stress relieving techniques such as going for walks, reading, listening to music, attending a yoga class, breathing exercises, meeting a friend for coffee, including just the right amount of exercises, fostering your social connections, striving for a life filled with purpose/passion/joy…
→ That also includes time spent outside, if possible. The fresh air itself will contribute to better sleep, but it really is the daylight that is important. It is so important in certain areas of the world that do not receive enough of it that super high rates of the medical condition called ‘Seasonal Affective Disorder’ or SAD (yes really, that’s the name) take place. With the main reason behind the development of that condition being that sunlight is vital for the creation of the feel-good neurotransmitter Serotonin. Therefore, lots of sunlight usually means more serotonin and it is that very same neurotransmitter serotonin that just happens to be the precursor to another important sleep hormone in the body, melatonin. Serotonin stimulates melatonin, so it makes sense the more sunlight that a person gets, the more serotonin that they will produce which then equates to more melatonin production, which prepares a person for sleep and is one of the biggest factors that can set the stage for a healthy circadian rhythm. It has also been shown that as a result, the brighter the light that a person can get in throughout the day, the better they will sleep at night because of that increase in serotonin production and resulting melatonin. That means sunlight serves as a trifecta, by the fact that it helps in creating a healthier circadian rhythm, it will make a person feel better and be more energized due to the increased levels of serotonin and lastly in that it can make a person fall asleep easier at night.
→ Make an effort to go outside daily, most beneficial would be within 30 minutes of waking, but some is better than none (lunch break, parking further away from work, get a dog to motivate you…). If you know you are not getting enough Vitamin D (which is the majority of people) make sure you supplement.
→ Blue light – Before the arrival of artificial lighting, the sun was the major source of lighting, and people spent their evenings in relative darkness. Now, our evenings are illuminated, and we take our effortless access to digital devices for granted. As the sun disappears, your body goes into a mode of sleep preparation. Ideally, blue light exposure should be limited as much as possible at night to ensure a healthy sleep-wake cycle. Unfortunately, aligning ourselves naturally is somewhat challenging in the digital age, especially if you’re prone to digital separation anxiety. For many of us looking at our phone is one of the first and last things we do on a daily basis. But research reveals that artificial blue light suppresses the secretion of melatonin, as mentioned the hormone that influences circadian rhythms. Blue light wavelengths, which are beneficial during daylight hours, but seem to be the most disruptive at night. In other words, our beloved electronics housing all our favorite apps, tools, TV shows, and games, keep us awake at night.
→ Setting your devices up with “night mode” is a start, but that does not block out the blue light completely.
→ Limit blue light exposure completely at least 30 minutes before bed (so keep phone out of the bedroom if possible) and wear blue light blockers 2-3 hours leading up to bed time.
Specific recommendations
→ Stick with the same bed time and rising time every day. Week day or weekend. One of the most beneficial things you can do in order to improve your circadian rhythm.
→ Create a bed time and a morning routine. For example: 2 hours before bed last meal, 30 minutes chores, 1 hour tv, – bed time alarm goes off (as a reminder to go to bed), switch off electronic, last 30 minutes before bed get yourself ready, read, lights off.
→ Invest in a good quality mattress, duvet and cushion. Ideally, you will spend 8 hours of your day in bed (1/3) that means, it is worth it!!
→ Keep your room dark. No artificial light and try to get good blinds to keep any outside light out as well. Alternatively wear an eye mask.
→ Keep your room quite or at least as much as you can. White noise can help blocking out some external sounds if you have noisy neighbors or wear ear plus
→ Keep your bedroom cool. Research shows that between 59.9-66.92 degrees Fahrenheit (or 15.5- 19.4 degrees Celcius) is an ideal temperature to go to sleep. Core temperature has to drop in order for sleep to be initiated that is why the ideal temperature is so important. Use fans wisely, choose the right bedding, get a bed cooler, take a warm bath (sounds counter productive, but studies prove otherwise). You can also consider taking contrast showers (10s hot, 20s cold, alternate at least 5 times).
→ Sleep trackers such as the oura ring can be helpful to generally determine how much time you spend in what phase of sleep. They can also help you determine your readiness factor for your training etc the next day. Nonetheless, use them wisely and keep in mind that no machine knows your body as well as you know yourself.
→ The bedroom is for bedroom activities only. No TV, eating, studying, working etc. in bed. Help your mind switching off by making that clear distinction between the location where we ‘go to sleep’ and where we do our ‘living’.
→ Keep animals out of the bedroom. Yes, you likely consider them as family members, but in the end your sleep comes first and animals move around and make noises, likely impairing the quality of your sleep.
→ Practice some kind of mindset work that helps you wind down, relieve anxiety and calm your mind before going to bed. For example breathing exercises, reading, doing a ‘mind dump’ (writing everything down that is on your mind so you don’t have to think about it at night)…
→ Travel recommendations: try to adjust to time zones straight away (switch your time to local time) and avoid napping throughout the day in order to adjust your circadian rhythm quickly (unless you are only there for a very short amount of time). Travel with ear plugs and eye mask and consider supplementing with 5g of melatonin 30 minutes before bed, in order to help induce sleep. Stick with your regular meal times (8am breakfast, 12 noon lunch etc.) to help your circadian rhythm even more.
Frequently Asked Questions:
Q: Can I split my sleep?
A: Split sleep (e.g. 4+4) is better than just generally short sleep (4-5 hours), but it is not the same quality of sleep as a full 8 hours sleep opportunity.
Q: Can I bank sleep?
A: Banked sleep (trying to sleep 10 hours for a few nights, because you know you have a few nights of sleep deprivation coming up) is better than not banking any, but it still can’t compare to 8 hours of sleep opportunity every night.
Q: Can I catch up on sleep?
A: Catching up on sleep is better than not catching up on sleep, but “damage” done by sleep deprivation cannot be ‘undone’ per se.
Q: But what if I am a night owl?
A: Yes, genetically we do have personal preferences as to what time of the day we are most productive etc. BUT research shows that if electronic lights and usual lifestyle factors are removed and people were placed in a natural environment without a clock – EVERYBODY would go to bed and rise with the sun.
Q: Is there such a thing as sleeping too much?
A: Yes, there is no exact number of hours, as this is rather person dependent, but most individuals operate best on 7-10 hours.
Q: How do sleep requirements change as we age?
A: As you get older, you sleep more lightly and get less deep sleep. So you spend less time in NREM-3. Aging is also linked to shorter time spans of sleep, although studies show you still need (and should try to get) as much sleep as when you were younger.
I hope you found this helpful.
If you want more detailed info on sleep I highly recommend the book “Why we sleep” by Matthew Walker. If you don’t like reading, he was also on ‘The Joe Rogan Podcast’.
Resources:
1. https://www.cdc.gov/media/releases/2016/p0215-enough-sleep.html
2. https://www.sleephealth.org/sleep-health/the-state-of-sleephealth-in-america/
3. https://www.theguardian.com/lifeandstyle/2017/sep/24/why-lack-of-sleep-health-worst-enemy-matthew-walker-why-we-sleep
4. https://blog.swanwicksleep.com/sleep-and-muscle-recovery/
5. https://ncicertifications.com/level-2-certification/
6. https://www.healthycell.com/blog/maximize-the-4-stages-of-sleep?gclid=EAIaIQobChMI-66To4iJ5wIVClYMCh3YbAe1EAAYAiAAEgIKbfD_BwE
7. https://www.sleepfoundation.org/articles/what-are-facts-about-insom
8. https://blog.swanwicksleep.com/bedtime-routine-tips/
