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How sleep affects sports performance

The three pillars of performing well in sport are training, nutrition and recovery. In recent years, good quality sleep has been recognised as a massive tool in improving athletic performance but how exactly does it help and what can you do to improve it? It's important to note that this article applies to anyone who is active. From olympic level athletes to recreational joggers and paddleboarders, good quality sleep will maximise the gains from your sport and allow you to continue to improve with less training effort.


When we sleep, our brains cycle through different stages. There are two key groups of sleep stages: REM (rapid eye movement) and NREM (non rapid eye movement). REM sleep is characterised by darting eye movements, hence the name, and is responsible for the cognitive benefits of sleep such as retaining a good memory, reducing brain fog and improving concentration. NREM sleep is responsible for the physical benefits of sleep like physical growth and development, the maintenance of hormone production and cardiovascular health. Each night we experience several sleep cycles; our brains go from light to deep sleep, dream sleep and then start again. If we are not getting enough sleep or our sleep is disturbed then we are not allowing our body the full benefit of all of the sleep it needs, and this includes using an alarm to wake up in the morning - if you need an alarm, your body is not ready to wake up yet! This information is important for anyone and a huge percentage of the population is chronically sleep deprived whilst masking it as being productive by fitting more into the same 24 hours, but it is extremely important to prioritise sleep, especially for those who are actively trying to perform well in sport.


So, how can sleep benefit sport?

The obvious thing to note is that those physical benefits of NREM sleep help our muscles to recover after exercising or training, but there are many many more benefits to add from improved fat loss, muscle growth, a more positive mood, higher self-esteem and mental health, to better technical skills and form whilst moving your body and therefore reducing your injury risk.


Weight loss

Lot of people exercise to maintain a healthy body composition. Many men and women in the general population want to lose fat and/or gain muscle and enjoy exercise as part of this journey, it is also important for elite athletes who want to be light on their feet whilst still maintaining good power, strength and agility. Numerous research studies prove that it is much easier to overeat when you are not sleeping enough. There are only two ways of getting energy - eating or sleeping. If you are tired it becomes much easier to reach for calorically dense high fat and high sugar foods. It's not a matter of poor willpower; it's years and years of evolution derived from a time when food was scarce and we were designed to find high calorie foods extremely pleasant so that we gorged on them to give us energy and didn't starve to death. Fortunately, food is no longer so scarce but it does mean that it's much easier to be tempted into a takeaway or a chocolate bar to give you a boost when you're feeling tired. Sadly, these highly palatable foods will often give us a sugar crash shortly after the energy boost and leave us feeling more tired than we did before. If you're chronically sleep deprived, this might be the reason you find it difficult to stick to a diet or are gaining weight. One study in particular found that not getting enough sleep is associated with overeating and significantly associated with obesity, particularly in women (Trace et al., 2012). Another found that having a lack of sleep or disturbed sleep reduced weight loss by 55% and increased the loss of lean body mass (muscle instead of fat) by 60% whilst also causing physiological adaptation to caloric restriction (meaning you have to diet harder and restrict calories further to lose the same amount of weight), increased hunger and a shift towards the oxidation of less fat when producing energy (Nedeltcheva et al., 2010). It's not just harder to want to lose weight when you're tired, your body makes it physiologically less possible too.


Muscle growth

Another benefit of exercise is growing muscle. From the extremes of bodybuilding and Olympic weightlifting to just toning up or wanting to be able to do your first press up, growing more muscle can benefit everyone. Testosterone is largely responsible for muscle growth and although testosterone is seen as the male sex hormone, it is produced by both men and women. The majority of testosterone release happens whilst we sleep so sleep deprivation or disturbance is linked with reduced testosterone levels, directly affecting the amount of muscle we can develop. Scientific research has highlighted the importance of sleep on testosterone levels. One study showed that daytime testosterone levels in young, healthy adults fell by 10-15% in just one week after sleep was restricted to five hours a night (Leproult and Van Couter, 2011). For context, the normal rate of testosterone decline as we age is 1-2% per year. If you struggle to prioritise getting enough sleep, or you're affected by a condition such as insomnia or sleep apnoea which is disturbing you at night, think about how much this could be affecting your athletic performance. Testosterone doesn't just help us to grow strong, it has also been proven to have positive effects on mood, self esteem and mental health so normal levels are essential for our wellbeing. Some athletes have been known for supplementing testosterone to get these benefits, which is banned in many sporting organisations. What they can do instead for the same muscle growth is simply get enough good quality sleep.


Circadian rhythm

We all have an inbuilt 24-hour body clock called our circadian rhythm which controls every 24 hour cycle experience including our sleep-wake cycle, hunger cycle and various hormone releases. This biological rhythm is regulated by both internal and external stimuli. Various hormones and chemicals inside of the body are released at different times of day to keep us on track, but external cues such as natural daylight, regular mealtimes and social interaction help us to adjust too which is why we can recover from jet lag. Two of the main hormones that can affect your sleep and your sport are cortisol and melatonin.


Cortisol is known as a stress hormone and is responsible for the fight-or-flight response in difficult situations but it has many other functions too. It helps to maintain normal blood pressure, increases glucose metabolism and reduces inflammation, as well as helping us to wake up every morning! Cortisol levels rise throughout the second half of the night and surge within the first hour of waking. This surge is known as the cortisol awakening response and is the reason you feel much more alert after getting up and about than you did when you first opened your eyes. Various health conditions can increase or decrease our cortisol awakening response which go on to increase or decrease our sleepiness and fatigue levels. The correct balance of cortisol is needed for normal functioning but modern life means that this response is stimulated much more frequently than it was ever designed for. Social media, negative scenes on the television and worry or stress from daily life can all stimulate the fight-or-flight hormonal response from cortisol which can make it difficult to fall asleep. This is the main reason a lot of people find it difficult to fall asleep after an evening training session. Intense exercise stresses the body and stimulates a cortisol response. This makes it harder to get enough good quality sleep and reap the benefits for your training, so it's important to prioritise doing these hard sessions earlier in the day if you can and allowing yourself plenty of time to cool down and relax your mind as well as your body afterwards.


Another key hormone that helps to regulate our circadian rhythm is melatonin. Melatonin makes us feel sleepy and is produced by the body when it starts to get dark (that's why you're advised to stay off of your phone and switch to dim lighting in the evening). Melatonin levels peak in the early hours of the morning and then reduce completely when we are exposed to daylight again. Melatonin also helps to regulate our neuroendocrine system and the right balance can improve control of our mood, development, immunity and overall health. Melatonin can be supplemented to induce sleepiness and is commonly used to help jet lag and insomnia (although it's important to note that simply increasing sleepiness will not solve the underlying cause of insomnia in the long term). Melatonin is slow releasing and keeps us asleep for many hours. It's difficult to sleep undisturbed when you're not in a dark environment because melatonin secretion is limited.


Jeg lag

Jet lag is a massive hindrance to elite athletes travelling regularly for competitions and training camps. Not only because of the discomfort from feeling sleepy in the daytime, but it limits performance. We all have a chronotype; some people are morning larks and some are night owls but most people sit somewhere in the middle. Research shows that physical performance is much better when carried out in the morning for morning-type people and the late afternoon for evening-types, so long as they've had enough rest (Facer-Childs et al., 2018). If you're typically an evening person, you're not going to be getting as much out of your training by forcing yourself out of bed with a coffee at 6am every morning for a hard session. If you then go and travel across six time zones in one flight and try to make your body perform at elite level at what would be 9am at home when you've only slept for 3 hours, you're not going to do as well as you could. For this reason, many sports teams are now looking into how they can reduce the effects of long-haul travel for their athletes.


Technical skills development

Sports aren't just about cardiovascular fitness and muscle tone. Most sports have a technical aspect to them; running requires your brain to recognise how to place your foot correctly to avoid injury, gymnastics requires extreme physical manoeuvres and basketball requires a lot of tricks and fast movements to excel. There aren't any sports which don't require some kind of skill. We know that REM sleep is essential for cognitive development, which also means it helps our memory to retain important motor skills developed whilst training. If you're learning to do a somersault on a trampoline, it's going to be much more controlled the next time if you've had a good night's sleep after practice. Not only is sleep imperative to maintain high energy levels and for your muscles to repair, but also to remember the movements required for the skills you have learned.


Caffeine

Caffeine is a stimulant typically found in tea, coffee, chocolate and energy drinks and is a huge part of many athletes' lives as well as within the general population. Caffeine does not lead to good quality sleep, but by no means should it be totally avoided. Research has shown that taking caffeine leads to higher performance under a lower perceived exertion. One study found that athletes who had consumed caffeine perceived weights that they were lifting to be lower than they actually were, and were therefore able to lift more, meaning they were getting more from their training (Felip-Stachnik et al., 2021). Similar results have been found in endurance athletes, who are able to exercise more intensely and for longer under the influence of caffeine.

The main concerns with caffeine are around timing and ethical use. If it is consumed too late in the day, it will limit your ability to fall asleep and hopefully after reading this article you will agree that the training benefits of sleep outweigh the perceived exertion benefits of caffeine. The other concern is that it is often used to mask the effects of genuine fatigue and overtraining. If you aren't feeling up to it, usually going home and having a good meal and some rest will bring your athletic ability up way higher than a strong cup of coffee and another intense session. You can't reap the benefits from training if you aren't allowing your body the rest it needs to adapt.


Caffeine affects your body very quickly, usually after about 20 minutes, and has a half-life (where half of the original caffeine content is still circulating your system) of 5 hours. This means that if you have a cup of tea or coffee at 3pm to get you through the rest of the day, it's not much different from having half a cup of tea or coffee 5 hours later at 8pm when you should be winding down ready for sleep.


Some people report a lower sensitivity to caffeine and are able to fall asleep quite easily under the influence of caffeine. Caffeine does affect everybody differently but it is highly likely that even if you are able to fall asleep, you quality of sleep isn't as good as it could be (and then you won't be getting all of the benefits of sleep listed above).


If you like caffeine and its effects on your sports performance then great. But have a cut-off so that its effects on your sleep are minimal. If you simply like the taste then try decaf in the afternoon (though note that it's low caffeine and not totally caffeine free). It is questionable whether the training benefits of caffeine can be a placebo in which case decaf options would still give you the same benefits. If it's not about the taste and you just need an energy boost before your session, try a different method. A cold shower or dip in the sea, a brisk walk outside or some high energy music can wake you up and get you feeling energised.


Alcohol

Lots of people believe alcohol helps you sleep. This is far from the truth and unfortunately, although you quickly drift off into unconsciousness, your brain isn't able to cycle so easily through REM (cognitive function) and NREM (physical function) stages of sleep. Alcohol, like many types of sleeping medication, leads you to into a period of sedation rather than sleep and limits the natural sleep cycles. You're not in a deep sleep, you're unconscious. This also explains why it is possible to choke on your own sick when you're intoxicated, where your body should otherwise be able to wake you up at the feeling of nausea. Alcohol isn't really conducive for athletic performance, but that's not to say you should totally avoid it if you do enjoy the odd drink. It can definitely still be enjoyed in healthy moderation as part of a balanced lifestyle where your mental and social wellbeing is just as important as your physical performance.


Drug abuse

Just like caffeine, stimulants such as cocaine and MDMA are becoming much more present among the sports community and are now the second most used drug for performance enhancement. Globally, both illicit and prescribed stimulants account for a large amount of drug use. The effects on alertness, fatigue and perceived readiness to perform are seen to be beneficial for long days training but the consequences are huge. Narcotics and stimulants negatively affect sleep quality and therefore the benefits that sleep has on your performance. Long-term effects of the drug themselves lead straight to negative health; cardiac arrhythmias, increased likelihood of stroke or myocardial infarction, high blood pressure and muscle tremors are all very common. The risk of sudden cardiac death in sport is massively increased with regular stimulant use and dependence can be noticed by sports coaches working with healthcare professionals when looking at ECG changes and inflammatory markers in their athletes.


Shift work

Unfortunately, shift work is essential to society. Doctors, nurses, firefighters, flight attendants, cleaners, shop workers and so many more are required to work shifts. The circadian rhythm is disrupted when somebody does shift work and this is not ideal for their training or sports performance. This is not to say you should go and get a new job, but just to be aware that the effects of disrupted sleep probably mean you can't put 100% into every session when sometimes your body needs to rest. Even some Olympic level athletes need to work standard jobs to earn money; we can't have it all but understanding how you can balance both by still maintaining a good number of hours of high-quality sleep will allow you to minimise the effects of shift work on your training and performance.


Hopefully this article has shown you that sleep really is more than just trying not to feel tired the next day, especially if you are trying to excel in your sport or learn new skills.


Sleep is free but investing in a good quality sleeping environment can make a huge difference to your daily life. Find a bed and mattress combination that really is comfortable and stick to good quality, 100% cotton bedding. Replace your pillows often and flip your mattress to make it last longer. Mattresses and bedding aren't cheap. Some might cost nearly as much a weeks holiday abroad but you will notice a monumental difference to every single day for up to 20 years (guarantees vary depending on mattress brand) by having a comfortable bed. That seven day trip to Spain you had in 2008 for the same money was fun, but hasn't impacted your life in the same way as a good quality mattress could.


Prioritising your sleep and rest periods should be just as, if not more important for sports performance than training. Without enough good quality sleep, your body isn't going to adapt as well as it could and you'll have to work much harder the same physical response. If your sleep is disturbed or you're suffering with a sleep disorder then seek help from a sleep specialist - it may be the best thing you ever do for yourself and for your team mates.