Sleep is a critical component of training. So what happens when you sleep and how can you make sure you are maximising one of the most powerful recovery weapons you have? Tom Craggs gives his thoughts…
Many look for performance improvements in all sorts of special products, fancy shoes and obscure diets. But they overlook the biggest performance enhancer available, a good night’s sleep. With boosts to growth hormone levels, improved kidney function and greater immune function, what else can help maintain consistency of high quality training like 40 winks?
Don’t take my word for it, below we go into greater detail and talk to experts about the power of sleep. Multiple studies have been undertaken on the subject so it’s not just something “Dave from the club” swears will make you faster, it’s evidence based advice.
How many of us really optimise our sleep? Below we look at why you need more sleep and how to improve the quantity and quality of your slumber. First, here’s why you should be prioritising your kip.
The benefits of sleep
Esther Goldsmith, sports physiologist with Orreco and St Mary’s University says “Sleep is critical for muscle repair, muscle building, bone growth and fat oxidation: all things that are going to help you adapt to training and progress as an athlete”. Good sleep can help athletes perform better in a number of ways;
Growth Hormone: Your body releases Human Growth Hormone (HGH) your deep sleep cycles (see below for more) and increases cell division and regeneration, in fact up to 75% of the growth hormone your body releases is thought to happen when you sleep. HGH is what you need to heal and repair damaged muscle fibres and tissues from those hard sessions…basically getting fitter!
Mental effects & stress: “Sleep also improves cognition and psychological functioning, as it can enhance neuronal connections, aiding memory and helping you learn” says Goldsmith “this is one of the reasons why, if you are practicing a new skill, you may find your ability dramatically increases the next day, after a night’s sleep”.
Injury Prevention: A US study showed that amongst a group of elite athletes those getting over 8 hours sleep a night had a massive 61% reduction in injury risk. Another study (Le Meur et al, 2013) showing athletes getting less than 8 hours sleep a night had 1.7 times greater risk of injury.
Look after your kidneys
Kidney Function: Poor sleep has been linked to inhibited glucose metabolisation & insulin release resembling type 2 diabetes and hypoglycaemia. It is at night when your kidneys also work to rebalance water and electrolytes – vital for athletes.
Improved diet: It’s a familiar story for many that when we are tired we tend towards lower quality foods to get energy in quickly and a great reliance on caffeine. A recent study confirmed that good quality sleep might see you eating more fruit and vegetables.
Immune Function: Goldsmith states that sleep also promotes the restoration of the immune, nervous and endocrine (hormonal) systems “these three systems that are important to keep in check in order to prevent injury and illness, and to keep absorbing training. Peaks of melatonin also occur when you are most likely to be asleep… and as melatonin has antioxidant and anti-inflammatory properties, it can help decrease oxidative stress which could otherwise impair and delay recovery”.
Just what are your ‘sleep cycles’?
You may have heard about ‘sleep cycles’ or ‘phases’ of sleep. In very basic terms as we sleep we move through a series of sleep cycles lasting roughly 90 minutes and within each cycle we move through different ‘stages’;
NREM (Non Rapid Eye Movement) 1: Light sleep, where we drift in and out of sleep easily, some people will feel muscle contractions and a falling feeling as gradually your eye movements and muscle contractions start to slow.
NREM2: In this phase your heart rate will start to slow and your eye movement will cease. Generally body temperature will also drop and brainwaves are slowed.
NREM3: This phase is typically a transfer from a lighter sleep to a deep sleep, with slow ‘delta’ brain waves interspersed with shorter more rapid brain waves.
NREM4: This is your deep sleep where rapid brain waves are much less frequent, this is the phase of sleep that will leave you feeling confused and disoriented if woken from.
REM: Rapid Eye Movement is characterised by more rapid brain activity that mimics a waking state but whilst still asleep and is when you will often experience more intense or vivid dreams.
How do we sleep?
After about 90 minutes your will move back to stage 1 for a new cycle, as the night progresses so you move through a series of cycles but the time spent in each stage will change, with the latter stages of sleep characterised by less time spent in deep sleep and more in REM sleep.
The important thing to recognise is that it is during your deep sleep (NREM 3 & 4) that your body undergoes the most beneficial changes. Goldsmith says “it is in stages 3 and 4 where the real magic happens. This is the beginning of deep sleep, and when growth hormone and androgens are released”. Interrupted sleep represents a problem because each time you wake to interrupt a cycle you go back to the start reducing or even limiting time spent in the most beneficial (in recovery terms) stages
It’s not just about the number of hours…
We commonly hear about a magical ‘8 hours’ of sleep being the measure of a ‘good night’s sleep’. Certainly it’s great to get more sleep with 7-9 hours being the recommended for adults but quality is also critical. Some people seem to be able to function well on less than 7 hours sleep a night and one of the possible reasons for this could be sleep continuity. The images below show sleep monitoring of two different athletes. The left image showing over 8 hours of sleep time but with very poor continuity, and the right image shows less than 7 hours sleep but with much better sleep quality.
With less interruptions to our sleep cycles we are likely to feel more refreshed than with more hours but of poor quality. There is also some evidence to suggest that short pre exercise ‘power naps’ of 20-30 minutes can play a useful role in mitigating the effects of poor sleep.
How do you improve your sleep?
What can you do to improve your sleep and get fitter and stronger as a result? Well the answer really is about observing what we call good ‘sleep hygiene’. Here are a few key tips to get you going;
Avoid light and radiation from screens: A recent study (Figeurio et al) showed that exposure light form electronic displays reduced melatonin by up to 22%. Melatonin is critical to your sleep and wake functions. Banish smart phones and tablets from the bedroom and aim, as much as possible to give yourself a 90 minute window pre-bed clear of these devices.
Develop a pattern: Try to develop a routine and pattern of both behaviours (i.e. when do you brush your teeth, when do you dim the lights) and time you get into bed. This can help get your body back into a more natural and regular sync of sleeping and waking.
Avoid stimulants: Avoid caffeine and alcohol late at night – both are sure fire ways of affecting both your ability to get to sleep and your ability to sleep uninterrupted. This is both through their ability to stimulate brain activity but also because of their diuretic effects.
Food and drink: Eating your last meal a good two hours before sleep helps to ensure that your body is not still trying to digest a big meal as you get into bed. Whilst its important for all athletes to be hydrated try to avoid drinking to excess in the evenings. Getting up to go to the toilet is a sure fire way of interrupting your sleep cycles! Some people, if they train or work late, might benefit from eating their main meal at lunchtime, with a lighter evening meal.
Relax! It’s obvious but most of us hope to relax, rather than continuously doing anything about it. Again this is about routines, perhaps for you it’s a bath, or a short period of reading before you get into bed, for some it might even be meditation. Dim your lights and create a calm relaxing environment away from stress and distractions of smartphones or TVs.
To the mattresses
Environmental factors: A good mattress can be one of the wisest purchases any athlete can make. The decision is very personal but your mattress is one of the biggest factors in how well you sleep. Think about keeping your bedroom cool and investing in a blackout blind to limit light pollution, particularly if you are in a town or city. Ear plugs can be useful if you live in a noisy area.
Control your stress: If you have a lot on your mind try to write down a list ‘to do’ for tomorrow. Clear these now from your mind before you go into your relaxing routine before bed. Thinking over and over about work, family or money worries (or even training or racing stresses) really wont help.
Controlled breathing techniques (such as tri-breathing where you breathe in for a count of three, hold for a count of three and breath out for a count of three) if you are very stressed can also help you start to calm down, and transition towards sleep. One of the really damaging effects of lack of sleep is that it also affects your ability to control stress. This can create a vicious cycle where stress increases, affects your sleep, which in turn affects your stress. Seek further support if you do have chronic stress issues.
Training times: Exercise in general terms appears to have a beneficial effect on your ability to sleep. Harder training sessions however can elevate cortisol and leave a sustained increase in heart rate. This can inhibit sleep so it is probably wise where possible to avoid harder sessions in the final 2-3 hours before bed.
Whilst sleep tracking technology is now readily available to athletes and coaches it should be approached with caution. Whilst used in this article to visually demonstrate the concept of sleep continuity the accuracy of these devices for accurate measurement of sleep needs to be questioned.
As with all technology within sport coaches and athlete need to consider the validity and reliability of the technology they use – for example a recent study showed wearable sleep trackers under reporting sleep by 25-49 minutes. Athletes should be mindful of collecting data just for the sake of it and coaches should consider the ethical and performance implications on using this kind of data and surveillance. After all most of us know when we have had a good or a poor night’s sleep.
To summarise Goldsmith says “increased sleep has been shown to improve performance, in both repeated sprints and more endurance-based time trials. Sleep deprivation, on the other hand, can cause worsened performance, decreased strength, and increased anxiety”. So look beyond just what’s in your plan and what you do with your trainers on. Sometimes the biggest improvements can come from recovering better.
Le Meur et al, 2013. In Recovery for Performance in Sport. Human Kinetics. 2013