There are times when we need to extend our days and borrow from sleep time. It might be to meet a work deadline, for travel, or you might have volunteered for an endurance challenge!
This year thousands of people will volunteer to undertake an activity for 24 hours to help raise money for homeless charity, Crisis . Bensons for Beds is supporting the challenge, and is encouraging people to stay awake for 24 hours around the summer solstice, Wednesday 21st June.
So, if you do need to stay awake, how can sleep science help you to perform at your best? There are three main systems which influence whether you stay awake, or you fall asleep: your 24-hour circadian rhythms (or body clocks), sleep pressure, and the stress system. This article looks at how knowledge of these systems can help you to plan your challenge, and how to stay awake when your body is expecting you to sleep.
How can you best prepare for an endurance challenge?
Is it better to ‘warm up’ to sleep deprivation by experiencing some long days in advance, or should you start well rested?
Research suggests that ‘banking’ extra sleep in advance of sleep loss can make you more resilient ( Rupp et al 2009). Going to bed early, or allowing yourself more time in bed in the morning for up to 2 weeks before sleep deprivation has been shown to blunt the falls in cognitive performance and motivation that you would usually expect. For example, a recent study in military tactical athletes found that 4 nights of extending normal sleep by 1 to 2 hours resulted in improvements in reaction time, executive functioning, standing jump distance, and motivation levels ( Ritland et al 2019).
The more hours you stay awake the sleepier you feel because of a build up of a drowsy-inducing chemical in the brain, called adenosine. It’s not entirely clear why sleep banking works, but the extra sleep might ‘pay back’ an existing sleep debt, and may help to re-calibrate sleep pressure so that there is less of a build up of sleep pressure on the following nights.
Even if you can’t get extra sleep for multiple nights, you can still benefit from a nap before your event starts, to minimise sleep pressure at the outset.
What’s the best time of day to start your challenge?
This is a tricky one, and might well come down to if and when your support crew are available to help spur you on to the finish!
Our wakefulness typically fluctuates every 24 hours as a result of our internal circadian rhythms , and sleep pressure, as shown in the diagram below.
Circadian simply means ‘about a day’. Our daily pattern of alertness follows a circadian rhythm, or 24 hour pattern, which is programmed into our DNA. The average person becomes gradually more alert throughout the morning, peaks in alertness around 5-6pm and then gets gradually more sleepy as it gets dark.
Alertness levels often dip between around 1-3pm. This is not always due to eating a big lunch! If you are very sleep deprived, the post lunch dip is usually more obvious. Our most sleepy time is usually around 2-4am in the morning, which coincides with when our body temperature is at its lowest.
In addition to the circadian influence on alertness, we also have sleep pressure, which builds up the more hours we have been awake, and can only be reset by sleep.
So… the toughest times for a 24 hour challenge are usually in the early hours of the morning, especially if you have already been awake for a very long time.
There is no ‘easy’ way to do a 24 hour endurance challenge, but do think about the role of supporters. If you have a crowd cheering you, the social support and excitement will help you to release adrenaline, which will make you feel more alert, and help you overcome the lows in energy.
You might decide to start and finish your challenge in the early evening. If you start soon after a late afternoon nap, this will mean you should be able to stay awake through the early hours of the morning with limited build up of sleep pressure. It will also mean that after the challenge, you will be able to get a full night of sleep to recover.
If you start your challenge in the morning, it will mean that when you finish, it will be harder to fall asleep, since your body clock will still be in daytime ‘alert’ mode. You will also have to tackle the 3 or 4am slump when you have a big build up of sleep pressure - but the fact that you are almost finished may give you a motivational advantage.
Ultimately your start time may depend on other people, so you may need some other strategies to help you stay awake..
How can you stay awake during an endurance challenge?
1. Signal to your body clocks that it’s daytime using light, food and movement
We have a master body clock in the brain which helps to regulate all of our other internal circadian rhythms. Although all these clocks tick over on a 24 hour cycle, we do rely on signals from the outside world to adjust these rhythms so that they keep us alert during the day, and recovering at night.
If you need to stay awake, you can deliberately increase your exposure to ‘daytime’ signals. The strongest of these is bright light. Bright light lands on receptors in the back of your eye and signals the brain to stay alert. When you are completing your challenge overnight, the easiest way to stay awake is to increase the levels of ambient light.
Your body clocks are also sensitive to food, movement and changes in temperature - though bright light the strongest effect. Food is a daytime signal. You will probably find that you don’t feel very hungry overnight, since appetite also follows a circadian rhythm. Plan how much fuel your body needs, which will depend on how energetic your activity is, and aim to space snacks out every 2 hours or so. Try to avoid very high sugar and high fat snacks overnight unless you need a lot of energy to complete your activity, since your digestive system is in recovery mode at night. Lots of sugar can also lead to a slump in energy as a rebound effect.
Some regular gentle movement will help you feel more alert, although obviously prolonged movement can add to fatigue.
Being too hot, or too cold, can also make you feel fatigued, so keep checking in with yourself and have a fan at hand if you’re too hot, or ask supporters to help control the temperature for you if you have your hands full. Ensure that you stay well hydrated - dehydration is a common cause of fatigue, and you may feel naturally less thirsty during the night, so make an effort to keep drinking.
Some studies suggest that social support can also delay your body clocks, making you feel more alert. There is no doubt that support from others - especially if they are lively and wide awake - will raise your motivation and help you stick to your goals.
2. Reduce sleep pressure with strategic use of caffeine, or prophylactic napping
Caffeine works by interfering with sleep pressure. Caffeine blocks the adenosine receptors in the brain, and temporarily tricks the brain into thinking that you’re not sleepy. Although this sounds ideal for an endurance challenge, the danger is that the effects of caffeine wear off at an unhelpful time, and you get hit by ‘the caffeine crash’. Too much caffeine and you may feel jittery or anxious, and it will be hard to get your recovery sleep afterwards.
If you start to feel sleepy, try a glass of water first, before reaching for caffeine..
The general advice for a typical day is not to exceed 400mg of caffeine over 24 hours, which is the equivalent of about 5 cups of instant coffee (c. 80mg per mug), or 2-3 cups of double shot espresso (c. 150mg per cup). If you’re feeling extremely sleepy at any point during your challenge, a strong cup of coffee could well be helpful to pep you up, and the effects should last for another 4-5 hours afterwards. It usually takes 20-30 minutes for caffeine to have its alerting effects, so allow time for the caffeine to do its work, before reaching for another cup.
Rather than waiting until you feel sleepy, it might be easier to stay alert if you try a small dose of caffeine at regular intervals e.g. 100mg every 4 hours overnight. This is because it’s easier to stay awake if you maintain alertness, rather than getting extremely sleepy and trying to recover. Hopefully during the day, natural light will be doing its alerting job. You can also buy caffeine gum which contains 50mg per tab, and will help you feel alert within 15-20 minutes.
As discussed above, another strategy for reducing sleep pressure is to nap shortly before you start your challenge. Naps of as little as 10 minutes have been found to improve alertness for several hours afterwards.
3. Use adrenaline to your advantage
Finally, although our circadian rhythms and sleep pressure are the two main systems which influence our alertness, we also have the ability to override sleep signals when our stress system kicks into action. For our ancestors, this was usually in response to danger. Our stress system is designed to help us fight or flee from a predator: adrenaline increases our heart rate and blood pressure, increases blood flow to the muscles, and fires us up for action. When we feel excited about something, and we want to live up to the expectations of our ‘tribe’ our stress system automatically kicks into gear.
Sharing your challenge on social media, talking to friends about it, and getting their support, will increase your motivation and help you rise to the challenge. Aim to connect with your support team at the toughest moments - mid afternoon, in the early hours of the morning, and towards the end of your challenge.
At the same time, remember this is for fun! Too much stress can leave you feeling frazzled, irritable, make it harder to concentrate and interfere with recovery sleep afterwards.
Focus on enjoying the ride, and the benefits that your fundraising will bring to others when you succeed. After the challenge, take time to relax and unwind before you finally get into bed.
To recover from your 24 hour challenge quickly, allow yourself one or two short naps if you feel like it, but try to save your main sleep for overnight, so that you don’t further disrupt your body clocks.