Sleep… it’s that beautiful sensory reset button that can fix just about anything and bring us to a whole new day. Regarded by the Dalai Lama as “the best meditation”, sleep has long been recognised as vital to our very being. Even the Irish of olde, learned folk as they were, maintained “a good laugh and a long sleep are the best cures in the doctor’s book.”

We all know sleep is an essential part of our daily lives, and that we feel better for it, but let’s face it, it happens every night as part of our routine, and we probably don’t give it much thought. How many know that sleep is the single most effective thing we can do to reboot our brain and body health each day? It’s even regarded by sleep science experts as Mother Nature’s best effort yet at contra-death.

Dr Dale Rae, senior researcher at the Division of Exercise Science and Sports Medicine in the Faculty of Health Sciences at the University of Cape Town (UCT), and Director of Sleep Science at UCT , puts it simply: without sleep, we cannot survive. There’s not a single creature on the planet that doesn’t need proper rest during a 24-hour period. Dr Rae explains why sleep is so vital:

Short term benefits

  • neural plasticity    Sleep enhances our motor skills by allowing us to process what we learned that day. Keeping our neural pathways active is super important for developing a good skills base. The classic wobbly first-time on a bike, ice skates, a pogo stick or a particularly technical section of trail is always better the next day following a good night’s sleep, as the brain has consolidated the lessons of balance we experienced. The next time we don skates, hop on a bike or take to trail, our technical ability will be that much better.
  • immunity   During the day we inhale and ingest pathogens. At night when we sleep, our immune system generates antibodies that defend us against those pathogens.
    “There’s strong evidence to show that poor sleep and compromised immunity go hand in hand,” says Dr Rae. Sleep also plays an anti-cancer role, destroying any cells that have mutated or become damaged during the daytime. A lot of that “health patrolling” happens during the night.
  • flushing toxins    Another important housekeeping role of sleep involves the glymphatic system, a waste clearance pathway for the central nervous system. During the day various toxins build up in our brain as metabolic waste products. At night-time the volume of the brain reduces slightly, and the extra cerebral spinal fluid produced then bathes the brain, allowing the removal of toxins from the brain into the glymphatic system and out the body as waste.
    “One of the toxins it removes is beta-amyloid, a sticky compound that accumulates in the brain, disrupting communication between brain cells, eventually killing them. Accumulated amounts of beta-amyloid is associated with an increased risk of developing Alzheimer’s disease,” explains Dr Rae.
  • recharging   Sleeping restores the energy stores in the brain and muscles.
    “Sleep reverses performance losses that are associated with extended wakefulness. The longer we’re awake, the more grouchy we become, we’re forgetful, we can’t multitask effectively, and we become lethargic. When we sleep, all that reverses so we can be on our A-game again the next day. Sleep is a reset button, a reboot.”

“All these factors are critical from the athlete’s perspective because they contribute to adaptation to training, refuelling, for muscle growth, development and recovery.”

Medium term benefits
• physical health:   chronic sleep deprivation makes weight gain more likely, seeing us more likely to develop diabetes and hypertension.
• mental health:   there’re not many mental health disorders that don’t go hand in hand with sleeping disorders. Sleep is critical for mood stability and for managing mental health.

Long term benefits
Chronic sleeplessness increases our mortality risk. The shorter we sleep, the sooner we’re likely to die. It also increases our risk of cancer and of cardiovascular disease like hypertension and stroke.


“Elite athletes know to value and prioritise sleep. You’ll not meet a super-athlete who doesn’t sleep 8-12 hours a night. It’s a non-negotiable part of their fitness regime, critical for high-level sports performance, and as important for quality training as good diet.”

For years science focused mainly on the cognitive aspects of sleep deprivation, but more recently the importance of sleep in athletic performance has come to the fore. A regular sleep routine is fundamental for muscle recovery, and it facilitates adaptation to training.
“During slow wave / deep sleep, the body goes into repair mode, fixing or replacing damaged cells, building the protein needed for muscles to grow, tweaking the metabolism to adapt to training demands, replenishing fuel supplies, and enhancing the neural pathways that allow the brain to successfully perform complex movement tasks. The better we sleep, the harder we’re able to train, and because we follow that with more good sleep, our adaptation to our training load improves – it’s a cyclical process.”

How best to do it?  Ideally those 8-12 hours should be in a single, consolidated sleep, sometime between sunset and sunrise, every 24 hours. Often, because athletes’ sleep need is so great, they need to supplement their nocturnal sleep with a nap during the day. That’s fine, but the golden rule of good sleep health is that napping should never be at the cost of the quality of your nocturnal sleep. so, six hours of sleep at night supplemented with a daytime nap is not the way to do it.

How much is enough?  The recommended sleep time for 20 to 65-year-old adults to achieve optimal physical and mental health is 7-9 hours a night. Slightly younger adults can add another 30 mins.
“There is no definite 8 hours – we all have different requirements. For some, six hours is fine while for others 10 is necessary, so there’s a fair degree of allowance for inter-individual variation. Also, our sleep need can change. When we’re ill or when we up our training load, our sleep need increases. There’re often seasonal differences – we sleep more in winter than in summer. Mental health also impacts sleep need – those suffering depression have a greater need for sleep. Through all variations, the key is to find our sleep sweet spot.

Should we rely on technology to gauge our sleep?  Dr Rae recommends we shouldn’t pay too much attention to sleep monitoring devices to monitor our sleep quality.
“I’m not convinced wrist devices like running watches have a good handle on sleep staging yet, they still have a long way to go before they’re accurate. If people are genuinely concerned about their sleep patterns, they’re best having a natural sleep study done with the professionals.”

Literally every cell in the body tells the time. This is our circadian rhythm, and it runs in 24-hour periods, coordinated by a master clock in the brain. We need an intact circadian rhythm for optimal health. Disruption to our body clock can affect our health as dramatically as can short sleep. That’s why people like shift workers, airline crew and long-haul drivers suffer.

Dr Rae says the key to working around our circadian rhythm is to know our preference for mornings or evenings. “We call that your chronotype. Assess whether you’re a morning or evening type, or whether you’re somewhere in the middle, and then build a sleep-wake schedule around that. You sould also eat and exercise in sync with your chronotype.”

“Morning people (or larks), which many South African runners tend to be because our races start early, have an early sleep time, early rise time. If they’re working according to their biological clock, they’ll naturally do most of their eating during the light hours, and have an early bedtime. Evening people (or owls) do the opposite – they work best scheduling their day around waking later in the morning, eating later in the day, training near the end of the day, having a late dinner time, and getting to bed late.”

Natural fit   Once we know whether we’re a morning or night person or somewhere in between, the time of day at which we train is important. To get the most out of our training, we should aim to do our sessions at a time that best fits our natural biorhythm.
“Research has shown that those morning-type runners who train in the morning have an advantage in morning races. Evening types, even if they need to race in the morning, still achieve better training in the evening, because later in the day is when they’re able to get the best out of their body – that’s when they can push themselves harder and therefore have a better quality session in the evening than they would in the morning,

Picture the scene: it’s 10pm and you’re about to start a 100-miler. You’ve been awake since 6am that morning, and you’d normally be about to hit bedtime. But you’re pumped with adrenalin and in full race mode, the last thing your brain wants to do now is sleep.
24 hours later, you’re now 130km in and still going, although weird things are happening. Not only are your legs completely sapped, but you can no longer keep food down, your eyelids feel like lead, and sleep monsters are creeping out from behind trees and rocks. Every cell of your being is screaming for sleep…

When the sun goes down and the light levels drop, our body produces melatonin, which signals to every cell in the body that it’s now entering rest phase. We can push through that for several hours, but the last two hours before dawn are the toughest, the body will be screaming for you to stop and rest. Through the night the body will have been given mixed signals: melatonin has been telling your body it’s in rest phase, but your brain has been forcing it to keep moving. On top of all this, you’ve been trying to stick to the golden rule of endurance running: to eat regularly.

“We’re not designed to eat once the sun has gone down. Melatonin and the dark hours changes everything – it’s very much a circadian thing: our digestion slows, our core body temperature drops slightly. Our digestion processes are simply not designed to deal with nutrients during the night hours, and rather than using the calories, the body naturally stores them. When dawn comes, melatonin production is then suppressed and the body shifts from rest phase to activity phase – the body temperature rises and our gut is  now ready to take in calories.”

What about adventure racing and non-stop multi-day events?
Enduring numerous days of sleep deprivation during any multi-day non-stop event will inevitably cause a desynchronised circadian rhythm, where the internal body clock becomes confused in relation to the sunlight. Some people are better able to tolerate that sort of disruption, they just manage to find a new rhythm, while others can barely continue the race.

Ryno Griesel and Anouk Baars are two well-known South African multi-day trail running heroes who have loads of experience pushing their bodies beyond the limits of fatigue during competition.

Among his numerous trail running endurance events, Ryno achieved the 210km Drakensberg Grand Traverse FKT with Ryan Sandes in 41h49 of continuous running. He is also a seasoned adventure racer, having competed in numerous races on the world circuit since 2006. But it was during his and Ryan’s FKT along 1 507km of the Great Himalayan Trail in Nepal in 2018 that Ryno experienced multi levels of progressive sleep deprivation. Enduring the ardours of high altitude, sub-zero blizzards and frostbitten fingertips was bad enough, but it was sleep deprivation over the 24 days that topped everything.

“From about 7 days in, ‘seeing’ sleep monsters and ‘hearing’ whispering voices became common, even during daytime – it often felt like we had a third team member! By the third week of practically non-stop running and self-navigation, I experienced the strangest lack-of-sleep agony, even to the point where I no longer felt sleepy. It was as though I was in an alternate universe, not sure if what was happening was actually real, pinching myself and mumbling where the hell are we?”

Ryno’s top 3 sleep-deprivation tips:
• For events up to 36 hours, I always plan to not sleep. If I think the event will last more than 36 hours, I will start sleeping on the second night, ideally an hour per night. I try to time that hour so that I wake up just before sunrise, because before dawn is when I feel most tired, and waking up knowing that the sun will soon rise is a significant mental boost. Also, during the first hour after sunrise the temperature tends to drop, which makes sleep harder and less efficient.
• I often supplement this strategy with a few 20 min power naps. I don’t find power naps rejuvenating, but they trick my mind into thinking it rested, so that I can get moving again to find a more sheltered spot to utilise my planned 60 min sleep optimally.
• If the event is longer, like 10 days or more, then my policy of 1 hour from the second night tends to become 2-4 hours, as we sometimes did in Nepal.

Anouk’s experience shows there’s not necessarily one correct technique for everyone. Anouk has several prestigious endurance races under her belt, including Ronda del Cims 170km, Transgrancanaria 269km and the 330km Tor des Géants. But it was her 450km Tor des Glaciers that was her most impressive achievement – she crossed the finish line as 1st woman and 25th overall, in just over 183 hours of continuous pushing.

Anouk’s approach is to not have a set strategy, and rather to sleep whenever she needs to.

“At 230km into Tor des Glaciers, I caught the lead woman, arriving 5 min after her at an aid station. She panicked and left the aid station straightaway. I was surprised because I had calculated that like me, she hadn’t slept for the past 18 hours. The aid station volunteers all looked at me, wondering whether I would chase her. Instead I lay down and slept like a baby for 1.5 hours. I knew that with sleep I would be faster than she could be on no sleep. There was still another 200km to go, and I was confident I would catch her again, and I did.”

Anouk’s top 4 sleep-deprivation tips:

• Don’t over-think it. Your body and mind really can survive without your full quota of sleep. In the same way, people panic because they haven’t eaten for eight hours. Sure, you’ll be hungry but you won’t die. The same goes for lack of sleep – you don’t need a long beauty sleep every 20 hours!
• If you’re mid-race and you can’t fight sleepiness any longer, then just sleep. You’ll feel fresher for it, your pace will increase and you’ll make up a lot of time. You just don’t need to sleep too soon.
• One-minute power naps are the bomb! Simply sit down next to the trail, programme your alarm for 1 min’s time, and hug your phone to your ear. (Be sure to set the right time!) These super-short naps will help fight off hallucinations for another 45 min, guaranteed.
• Avoid coke, coffee and other caffeinated drinks for the first 24 hours of the race. That way, when you have them from day 2 onwards, the effect will be like rocket fuel. You’ll be an owl on steroids!


Dr Rae warns that sleep deprivation has a considerable effect on immunity. An athlete’s propensity to develop upper respiratory tract infections after a long race is not only about fatigue, it’s very much about the system having not kept to its natural cycle of cellular restoration and recovery.
“During ultra-distance or multi-day non-stop events, the body is unable to do its regular household cleaning processes, nor is it able to defend itself as it should.”

Can you train yourself to handle sleep deprivation?
“That’s a tough question. The scientist in me says to rather bank the sleep and deal with the impact of the race as well as you can. But there’s evidence from military studies showing how over time respondents become accustomed to broken and mistimed sleep, they adapt to it. So there’s probably a combination. But when it comes to optimising our adaption to training, and looking after our immune system, we need to sleep well. But there’s much to be said for practising, as that’s when we learn what our body feels like when it’s sleep deprived, and the various ways to cope.”


Know your body clock so you can sleep and train in sync with it as much as possible.

Be honest with yourself in finding your sleep sweet spot. Once you’ve figured out what it is, do your best to hit that target as often as you can. See it as a training goal.

Routine is critical. Be as consistent with your sleep as you can, from day to day, week to week, all year round. Obviously there’ll be occasions when you’re not able to keep to your sleep routine, and you can wipe out that night without stressing about it. The general rule is that in any given week, you want no more than a 90 min variation for your bedtime and wake-up time, and no more than a 90 min variation between your shortest and longest sleep. Strive for consistency. See it as part of your training programme.

Importantly, you need to allow times when you don’t worry – just relax, don’t stress about it, have fun.

If you have an underlying sleep disorder, it needs to be addressed. Ignoring it can be harmful to your training efforts and your physical and mental wellbeing.

Follow the general principles of good sleep hygiene:
– avoid stimulants (caffeine etc.) in the latter part of the day
– avoid eating late at night
– avoid excess light at night
– ensure you have a window of chill time the hour before bedtime – no work, no eating, no training, no electronic devices, no excessive light, nothing that’s stressful. It gives the brain a chance to switch into “rest-and-digest mode” so that sleep is more likely to come.