Introduction to sleep: The link between athletic performance and sleep
Updated: Feb 1, 2022
Introduction: fundamentals of sleep
Let’s get this straight, sleep is imperative to improving your athletic performance. Some scientific studies have actually touted that sleep trumps nutrition. This is predominantly due to the fact that the body can survive up to approximately two months without food (Kottusch, P., et al. 2009), whereas a study conducted in 2018 looked at 476 (selected 21 for inclusion) articles that pertained to sleep deprivation and found that symptoms such as perceptual distortions, anxiety, temporal disorientation and irritability started within 24-48hr of sleep loss (Waters, F., et al 2018). On top of that, “complex hallucinations and disordered thinking after 48 – 90 h” (Water, F., et al 2018). As you can clearly see, sleep deprivation can cause serious side-effects within a short time frame. However, I do not like to put one over the other, because they are both of critical importance in regard to performing optimally both cognitively and physically. As endurance athletes, we are constantly pushing our physical and psychologically capabilities – developing new thresholds as we adapt to the change in training stimulus. The big question becomes, how do we speed up those adaptations, adequately recover, and improve our capabilities within our chosen endurance sport? Over this 'sleep optimisation' series (starting with the fundamentals), we will uncover this multi-faceted concept in an easy to digest way – combining scientific articles and anecdotal experiences. Why even look at sleep? Let’s just say that you are building a house – you start with the foundation, right? You can’t just put the walls up, roof on, and attend to the small details. Sleep is just one element in that foundational mix (others include nutrition, mentality, and supplementation), so we have to get it right to build the house of our dreams. Since being a young adolescent, I’ve always been enamoured by the role nutrition plays in sport; however, sleep really never popped up on my radar until I stumbled upon an article written by ‘Whoop’ that mentioned the importance of sleep in regard to unlocking your athletic potential. In hindsight, it makes sense, considering that we spend approximately 26 years of our life sleeping. I was putting in the training, eating right; however, I just didn’t feel like I was smashing my workouts – the dull feeling of a lack of energy radiated throughout my body all day and this lead to me slowly starting to accept that feeling, as it must have been associated with all the training that I was doing. I do associate some of that feeling with the rigorous structured training, but once I started to focus on improving my sleep and had a device to record my experimentations, my energy levels went through the roof – which not only allowed me to improve my FTP (functional threshold power) at a faster rate prior to focussing on my sleep quality, quantity, and consistency, but my cognitive awareness and energy was elevated to new heights. In short, through anecdotal experimentation and scientifically peer reviewed articles, I was able to optimise my sleep environment and in return, improve my sleep. Now is the time for you to take your sleep performance into your own hands and not only improve your potential on the bike, running, swimming, or whatever endurance sport you are into, but to enhance your cognitive functioning, energy, and overall happiness in life. At the end of introduction, I implore you to dedicated a blank journal to writing down how you feel after every night, experimentations that you’ve tried prior to sleep, and your sleep environment for that night. Thank me later.
Sleep quality, quantity, and regularity
Normal and healthy sleep is characterized by good quality,quantity, and regularity(Medic, G., et al 2017). To understand the role in which sleep plays in your physical and cognitive abilities, it’s necessary for you to understand the different stages of sleep. Traditionally, sleep has been divided into two categories:REM (rapid eye movement)andNREM (non-rapid eye movement). NREM is composed of four different phases – stage 1 being the transitional movement from wakefulness to sleep. This stage usually lasts 1 to 7 minutes (Carskadon and Dement, 2005), essentially, this is when your mind and body start to wind down from wakefulness – your breathe slows and your brain activity transitions to low-voltage, mixed frequency waves (Carskadon and Dement, 2005). It’s important to note that during this phase, you can easily be woken up. With this being said, I have compiled tips and tricks to ensure that you improve your sleep quality and ensure you enter the critical stages that are responsible for physical and cognitive restoration. Moving on, stage 2 lasts about 10 to 25 minutes (Gais, S., et al 2002), and is between 45 to 55 percent of a sleep episode (Gais, S., et all 2002). During both stage 1 and 2, your body begins to relax, heart rate slows, body temperature begins to drop, and your respiration starts to slow. Now onto SWS (slow wave sleep) stages 3 and 4 of NREM – you’ve probably heard of this, right? If not, this stage is responsible for promoting muscle growth, repair, release of growth hormone and waste removal within your brain. As endurance athletes, we want to pay particular attention to muscle growth, repair, and release of natural growth hormone. According to the 'NCBI: Role of sleep and sleep loss in hormonal release and metabolism', there is actually a ‘dose-response’ relationship between slow wave sleep (NREM stage 3 and 4) and growth hormone release. In fact, during this stage of sleep, the body produces 95% of its required growth hormones(whoop, 2019). Without going into tremendous detail, we want to ultimately maximise this phase of sleep – typically, 23% of your sleep should be SWS (Whoop, 2019); however, healthy adults get anywhere between 1 to 2 hours a night. Now that we understand the importance of SWS, let’s dive into REM. REM is characterised by dreaming and memory consolidation (most of these) – your breathing, heart rate, and blood pressure all increase during this phase, which is similar to being in a wake state (NIH, 2019). During this mentally restorative stage of sleep, your brain consolidates short term memories and makes them into long term ones. According to the scientists at Whoop, healthy adults should get between 20-25% of REM a night (Whoop, 2020), so just say that you get 7-8 hours of sleep a night, that is equivalent to an hour and a half (90 minutes). Before we move on, it is important to note that your body goes through cycles of these phases several times per night. Now that we have a basic understanding of the phases of sleep and types of sleep, let’s look at the concept of ‘circadian rhythm’. Your circadian rhythm, also known as your internal ‘body clock’ consists of a series of biological processes that are designed signify sleepiness and wakefulness over a 24 hour period. This process is trigger by light – which is why you start to feel drowsy when the sun is going down and awake when the sun is rising/up. If you’ve ever been camping, you will probably notice this process in full effect, as you aren’t inundated with artificial light – which delays the release of melatonin, which is a hormone made by the pineal gland and is responsible for telling your body when to sleep and wake up. Since there is an absence of artificial light (phones, laptops, tablets, light emitting diodes *LEDs, fluorescent bulbs, and so forth), your body will recognise the natural cues in regard to when to go to bed and release the hormone melatonin – making you feel tired. Do we all have the same circadian rhythm? Nope. This all depends on your age – are you a teenager? Someone over the age of 65? Or are you between the ages of 18 and 25? Depending on the recommended sleep needs, you will have to either create an artificial environment that mimics that natural rise and fall of the sun or create an appropriate sleep schedule that is situated around the natural fluctuations. For the purpose of this guide, we will say that most individuals reading this are between 18 and 64. According to US and Canadian recommendations, for individuals between the ages of 18-64 years of age, it is anywhere between 7-9 hours of sleep (Chaput, J., et al 2018). However, for most of us, the reality of the situation is that we can’t just go to bed when the sun goes down and get up when the sun comes up due to obligations that prevent us from doing so. This is where we really need to focus our attention on creating an artificial environment that promotes the regulation of our circadian rhythm. This means incorporating strategies that will optimise your sleep quality and quantity. First off, the science suggests that exposure to light does indeed suppress the secretion of melatonin from the pineal gland. In fact, there was a study done by Harvard University that found out that blue light in particular suppresses melatonin - even more than other forms of light (Harvard Health Publishing, 2020). The study looked at the effects of participants who had 6.5 hours of blue light exposure vs green light. The evidence showed us that melatonin was actually suppressed for twice as long as the green light – shifting the circadian rhythm (Harvard Health Publishing, 2020). Simply put, blue light severely disrupts our sleep, therefore impeding our ability to perform to the best of our ability. Now that we know the recommended sleep duration (as per USA and Canada guidelines) , you're probably thinking 'What if I fail to get between 7 and 9 hours? Well, scientists now have enough evidence to know that there is an increased prevalence of different disorders the creep up with anything less than six and a half hours(Worley, S., 2018).
I do want to stress the point that it really is about quality and not necessary quantity. For example, you could be getting between 7-9 hours of sleep, but if most of that is light sleep or in an ‘awake’ state, you aren’t receiving the influx of GH (growth hormone), muscle repair, and cognitive repair/memory consolidation. This will most certainly impact your ability to perform on the bike, on the track, in the swimming lane or whatever your endurance sport requires of you. Great, now that we know the basics on the importance of NREM, REM, and how much sleep you need to optimise your athletic performance, we need to look atsleep consistency.Just say that you’ve been getting less than 7-9 hours (most days) of sleep Monday to Friday as you have pre-determined obligations such as a full time job, kids, family commitments, and so forth. Like most of us mere mortals, we try to ‘catch up on sleep’ on the weekends to make up for lost sleep during the week or you have social outings that run late into the evening, forcing you ‘sleep in’ past your usual ‘week day’ wake up time. Sound familiar? Well, sorry to break it to you, you’ve got it all wrong. Research suggests that anirregular sleep schedule can actually produce a myriad of negative consequences, such as an increased chance of obesity, high blood pressure, diabetes, and stroke (Breus, 2020). In fact, according to Dr. Michael Breus, “for every one hour change in how long someone sleep from night to night, there was a 27% higher chance of developing metabolic syndrome, which is a group of conditions that increase your risk of heart disease” (Breus, 2020)” - this study was pulled from Harvard University last year. Okay, so, we need 7-9 hours of consistent high-quality sleep (SWS and REM), but what about if you consistently sleep more than the recommended 9 hours? Again, sorry to break it to you, that’s not recommended either. According to Cappuccio et al in the article ‘Sleep duration predicts cardiovascular outcomes: a systematic review and meta-analysis of prospective studies’, too much sleep (important to note that it’s regular) is “associated with adverse health outcomes, including mortality, type 2 diabetes, hypertension and respiratory disorders” (Cappuccio, F., et al 2011). I mean, periodically getting more sleep than needed, shouldn’t be too detrimental to your performance or health. Now, how do we actually improve our sleep quality? Over the years, I have recorded what does and doesn’t work for me – which is partially anecdotal, but the methods behind the advice are research driven. Now that we have established that we need 7 to 9 hours of sleep (consistently going to bed and waking up 7 days a week at the same time – with no more than a 30 minute fluctuation, high quality REM and NREM) how do we achieve this? Well, lucky for you, I have compiled a series of techniques that will completely revolutionize the way you feel and perform (basics are addressed within this blog). The first piece of advice is no fashion statement, I can guarantee you that. I swear by blue light blocking glasses – so much so that I don’t go anywhere overnight without them, regardless of how I look. In essence, blue light blocking glasses have a filter over the lens that prevent the blue light from penetrating your eyes. A study done by Lancaster University showed that blue light blocking glasses showed promising results when it comes to circadian disregulation (Algorta, G., et al 2018). Personal electronic devices actually emit more blue light than any other colour (Gringras, P., et al 2015). Although there isn’t complete sound science behind blue light blocking glasses – as the studies are typically quite small, it is a small investment that can reap tremendous benefits. Harvard researchers found that “blue light suppressed the release of melatonin for about twice as long as the green light and shifted circadian rhythms by as much (3hrs vs. 1.5 hours)”. (Harvard Health Publishing, 2020).
To maximise the benefits, you should wear them around three hours before bed to promote the release of melatonin. Along with the glasses, it is highly recommended that you eliminate sources of light that can be avoided, such as the TV, computer, phone, and so forth. Glasses typically cost around 80 to 120 dollars and can be well worth it. How do you know that they are working? Well, beyond feeling more refreshed in the mornings (which could potentially be a placebo effect), you can gauge the difference between how much REM and NREM you receive throughout the night with a sleep tracking device such as WHOOP or the Oura ring (ZERO affiliation with either company). I was sceptical prior to purchasing my Swannies (glasses), but the difference was noticeable after analysing my sleep data. Once you have your glasses and picked your sleep routine, you then need to create the ideal sleeping environment. This should include blackout blinds (limiting light exposure), setting your room temperature prior to bed, incorporate white noise into your room, wear a sleep mask (optional/subjective), and use earbuds (if noise is an issue). When creating this ideal sleep environment, it is paramount that you nail down the perfect temperature. This is mainly due to the fact that wakefulness and disrupted rapid eye movement sleep and slow wave is directly correlated to heat and cold exposure (Mizuno and Mizuno, 2012). Your body has an internal thermometer (thermoregulation) and this fluctuates throughout a 24hr period (circadian rhythm). Have you ever noticed that your feet and hands get slightly warmer when you are just about to jump in bed – or around nighttime? Well, this is your bodies way of releasing heat, since your internal temperature begins to drop when the sun goes down. Interestingly enough, a 2012 article suggests that “heat exposure affects SWS and REM, whereas cold exposure does not affect sleep stages” (Mizuno and Mizuno, 2012). This study further stresses the point that temperature is of critical importance in regards sleep quality. Another study used data from 765,000 respondents from 2002 to 2011, showed that an increase in nighttime temperature lead to insufficient sleep (Obradovich, N., et al 2017). These insufficient sleep patterns were largely due to the warmer temperatures, thus, keep your room on the cooler side (18.3 – 18.5 degrees Celsius). These tips/pieces of advice are just the fundamentals of improving your sleep quality – stay tuned for blogs that pertain to specific measures (meditation, supplementation, sleep devices *specific technological equipment, sleep hygiene and so forth) that you can implement into your own life to optimise your sleep.
1. Kottusch, P., Tillmann, M., Puschel, K. ‘Survival time without food and drink’. Arch Kriminol. Nov-Dec 2009; 224(5-6): 184-91. (https://pubmed.ncbi.nlm.nih.gov/20069776/)
2. Waters, F., Chiu, A., Atkinson, A., Blom, J. ‘Severe Sleep Deprivation Causes Hallucinations and a Gradual Progression Toward Psychosis With Increasing Time Awake.’ 2018; 9: 303. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6048360/)
3. Medic, G., Wille, M., Hemels, M. ‘Short- and long-term health consequences of sleep disruption.’ Nat Sci Sleep 2017; 9: 15 1-161. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5449130/)
4 Institute of Medicine (US) Committee on Sleep Medicine and Research; Colten HR, Altevogt BM, editors. Washington (DC): National Academies Press (US); 2006.
5. Carskadon M, Dement W. Normal human sleep: An overview. In: Kryger MH, Roth T, Dement WC, editors. Principles and Practice of Sleep Medicine. 4th ed. Philadelphia: Elsevier Saunders; 2005. pp. 13–23.
7. Whoop, 2019 (https://www.whoop.com/thelocker/stages-of-sleep-cycles/)
10. Chaput, J., Dutil, C., Kanyinga, H. ‘Sleeping hours: what is the ideal number and how does age impact this?’ Nat Sci Sleep. 2018; 10: 421-430. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267703/)
11. Harvard Health Publishing Harvard Medical School. ‘Blue light has a dark side.’ 2020. (https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side)
12. Worley, S. ‘The Extraordinary Importance of Sleep – The Detrimental Effects of Inadequate Sleep on Health and Public Safety Drive an Explosion of Sleep research.’ 2018 Dec; 43(12): 758-763. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6281147/)
13. Breus, M. ‘Why a Regular Sleep Schedule Matters to Your Health.’ 2020. (https://thesleepdoctor.com/2020/03/21/why-a-regular-sleep-schedule-matters-to-your-health/?cn-reloaded=1)
14. Algorta, G., Meter, A., Dubicka, B., Jones, S., Youngstrom, E., Lobban, F. ‘Blue blocking glasses owrn at night in first year higher education students with sleep complaints: a feasibility study.’ 2018;4: 166 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6211454/)
15. Gringras, P., Middleton, B., Skene, D., Revell, V. ‘Bigger, brighter, bluer-better? Current light-emitting devices – adverse sleep properties and preventative strategies.’ Public Health, 2015. (https://www.frontiersin.org/articles/10.3389/fpubh.2015.00233/full)
16. Cappuccio, F., Cooper, D., D’Elia, L., Strazzullo, P., Miller, M. ‘Sleep duration predicts cardiovascular outcomes: a systematic review and meta-analysis of prospective studies’. European Heart Journal, Volume 32, Issue 12, June 2011, Pages 1484-1492. (https://academic.oup.com/eurheartj/article/32/12/1484/502022)
17. Mizuno, K., Mizuno, K. ‘Effects of thermal environment on sleep and circadian rhythm.’ J Physiol Anthropol. 2012;31(1):14. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3427038/)
18. Obradovich, N., Migliorini, R., Mednick, S., Fowler, J. ‘Nighttime temperature and human sleep loss in a changing climate.’ Sci Adv. 2017 May;3(5). (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5446217/)