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Sometimes, the best thing you can do for tomorrow’s workout is get a little more sleep tonight.
Fitness folks are really good at adding things to the training program.
More kilometres, more gym workouts, more carbs, more gadgets and more ways to convince ourselves that one more session will take us from amateur to Olympian.
Sleep, meanwhile, tends to get whatever time is left over. We treat it as an optional extra rather than part of the plan.
As the Head of one of Sydney's most popular running communities, Coogee Run Club, I should probably know better. But going to bed early has never been my strong suit. I know I'm doing myself a disservice, yet somehow I convince myself that a good attitude and sheer commitment will make up for it when my 5am alarm goes off.
Because training is something we actively do, it's easy to think of sleep as the passive bit. The time when we're not working out or doing anything particularly productive.
Except our bodies are doing plenty.
Sleep isn't simply the gap between one session and the next. It's when the body gets to work on the physical and mental processes that help us recover and adapt to training.
So, while we're busy chasing the next secret to getting fitter, we might be overlooking one of the most basic parts of the plan: getting enough sleep.
How sleep supports exercise recovery
We tend to think of training as the hard part. That's where the work gets done.
But training is only the stimulus, according to Nathan Cross, a sleep neuroscientist at the University of Sydney. He says the work your body does afterwards is what allows you to recover, adapt, and come back ready to do it all again.
“Sleep is one of the key foundations of recovery, supporting both physical and mental restoration after exercise,” he says. “When sleep is consistently inadequate, recovery can be slower and performance can suffer.”
Professor Danny Eckert, a sleep and respiratory physiologist at the University of NSW, describes sleep as “essential” for repair.
“Certain hormones, such as the growth hormone – which is important for a range of functions relating to exercise performance, including protein synthesis which is needed to help build and repair – are almost exclusively only released during deep sleep,” he says.
But reducing sleep to a nightly muscle-repair session would be missing half the story.
Dr Rick Wassing from Macquarie University's School of Psychological Sciences, says it's time to rethink what we believe happens when we're out for the count.
“Sleep is not a passive time of unconsciousness; it is a different state for our body to actively engage in biological processes,” he explains.
“When the body is in this sleep state, it can engage in tissue repair, immune functions and metabolic regulation processes that are otherwise not possible during wakefulness due to competing requirements that are necessary during wakefulness.”
But it's not just our aching limbs that benefit from a night's recovery. Our brains do, too.
“Sleep is also crucial to recuperate from mental and cognitive stressors, not just physical stress,” Dr Wassing says. “This supports building resilience and emotion regulation such that we are better equipped to deal with stressors the next day.”
Which is pretty important, because training asks a lot more of us than simply moving our bodies. We're making decisions, managing discomfort, navigating goals, and, sometimes, trying to convince ourselves this is still a very good idea.
“For athletes, this means recovery is not simply about repairing muscles after exercise,” Dr Wassing adds. “Sleep also supports the brain including processes involved in learning, memory, and emotional regulation all required to make the most of next day training sessions.”
That means recovery isn't simply about waking up without sore legs.
Your brain has had a workout too – processing all the physical stress of training, the mental effort of getting through it, and everything else life threw at you that day.
How much sleep do we actually need?
This is where things get a little less straightforward than the classic “you need eight hours” advice, because there is no magic number that works for every person, every night.
“Generally, when you wake up feeling ‘refreshed', you had sufficient sleep,” explains Dr Wassing, which he admits might be an unsatisfying answer, but “there is no single amount of time for an individual”.
“Our sleep needs can also vary from night to night, and our bodies have sufficient redundancies to deal with some variation in sleep duration across the nights.”
That doesn't mean we should throw the sleep calculator out the window. Professor Eckert says there's evidence that elite endurance athletes need more sleep, and that getting over eight hours can boost performance.
But, again, the waters are very muddy.
“Training probably changes sleep pressure and sleep architecture, but we don't actually have strong evidence for a neat dose-response rule such as ‘every extra hour of training requires X minutes of additional sleep',” Dr Cross explains.
In other words, there's no spreadsheet where you can enter your 12 kilometre long run or 60 minute gym session and be told exactly how many hours you've earned in bed.
What we do know is that sleep needs can fluctuate.
“People may need more sleep for one or more successive nights after a day of high physical or mental stress,” Dr Wassing says.
And it's not only quantity that matters.
“You can sleep for eight hours with long blocks of NREM (Non-Rapid Eye Movement) and REM (Rapid Eye Movement) sleep, or you can have eight hours of sleep with lots of stage-shifts and awakenings,” explains Dr Wassing. “The latter would not be as restorative as the former.”
So, rather than chasing an arbitrary number, focus on getting enough quality sleep to support your training and the rest of your life. The goal isn't to win at sleeping. It's to give your body enough time to recover.
One bad night won't ruin your training
If you've ever turned up to a workout after a terrible night's sleep and convinced yourself your legs have forgotten how to work, you're not alone.
Professor Eckert, a sleep and respiratory physiologist, says sleep is one of the most important factors influencing endurance performance in the short term.
“It is probably the most important acute modifier of endurance performance with a 10% impairment in endurance performance with just one night of sleep deprivation,” he says.
However, Dr Cross points to research that challenges the common assumption that one poor night of sleep destroys physical performance.
“Some experiments show clear reductions in strength, power, muscular endurance and neuromuscular function after sleep loss, while others find little or no impairment after a single poor night,” he explains.
The impact becomes more noticeable when sleep loss is more severe or happens over several nights, and some aspects of performance are affected more than others.
“Specifically, cognitive-motor performance, vigilance, decision-making, and perceived effort are likely to suffer more than physical performance,” the sleep neuroscientist says.
In other words, sleep deprivation might affect your brain before your muscles, but researchers are also beginning to explore whether consistently training on too little sleep affects how your body adapts and improves from exercise.
That distinction matters. Training isn't just about getting through a session; it's also about how your body responds afterwards.
“Many of the adaptations we want from training – like repairing and building muscle and changing metabolism – occur afterwards,” the sleep neuroscientist says. “Experimental studies now suggest that sleep restriction can alter some of these processes, including muscle protein synthesis and the molecular response of muscle to exercise.”
So, while one restless night isn't a reason to cancel your workout, you don't want to consistently be training on empty.
Can a wearable sleep tracker help you sleep better?
Those who love fitness love a good data point. We track our kilometres, pace, heart rate and splits like our lives depend on it, so naturally, we want to know what our bodies are doing while we're unconscious too.
Smartwatches and other wearables give us a snapshot of what's happening overnight, helping us spot patterns and understand how our habits might be affecting recovery. If you're consistently going to bed later than planned or clocking less shut-eye during a busy training week, having that information at your fingertips can be a useful wake-up call (pun intended).
But, as with any fitness metric, it helps to know what the numbers can – and can't – tell you.
UNSW's Professor Eckert says consumer-grade devices do a pretty good job of tracking sleep timing and duration, and can be useful in tracking trends over time.
Dr Wassing adds: “Bedtimes and total sleep time are the two most accurate measures and trends over time by these two measures can be more useful than treating a single night's score as precise.”
However, both experts say wearables can sometimes overestimate sleep duration by around 30-40 minutes, and that if you want a deep dive into the different sleep stages, you'll need to directly monitor brain activity.
The trick is not to get too caught up in the data, but to think of your wearable as one piece of the puzzle. It can help you become more aware of your habits, spot patterns and make small changes that help you feel and perform at your best.
Your body loves a routine: How to improve sleep for better training and recovery
The good news is that improving your sleep doesn't necessarily require an elaborate nighttime routine, a new supplement stack or Egyptian cotton sheets.
“Consistent wake time is the single most powerful anchor for circadian rhythm and sleep quality,” Dr Wassing says.
Professor Eckert adds: “When it comes to sleep, our bodies love routine, so ensure that you not only allow enough sleep opportunity each night, but keep a regular sleep/wake schedule.”
Going to bed at a different time every night and catching up on sleep whenever the weekend rolls around might feel harmless, but a study from Flinders University suggests that irregular sleep timing is associated with a higher risk of high blood pressure¹. The relationship isn't as simple as one late night being bad for you; it's the pattern over time that matters.
“Just varying the time at which people go to sleep by more than 30 minutes on average throughout the week, independent of the amount of sleep they get, is also associated with a 30 percent increased risk of having high blood pressure,” he says.
“If you shift this number out to 90 minutes, the association with hypertension increases to 90 percent.”
Dr Wassing says we should also be mindful of daytime naps. “Particularly long or late naps, because they can reduce sleep pressure at night,” he says.
Your next training upgrade should be bedtime
If you're like me, you're always looking for the next thing that will make you fitter. A new shoe. A better training plan. Another strength session. Whatever might give us that extra edge.
But while we're busy fine-tuning our workouts, it's worth asking whether we're giving our bodies enough time to recover from them.
Sleep won't replace consistent training or good nutrition, but getting enough of it can help support the work you're already putting in.
Personally, I could start by treating my 5am alarm as a reason to go to bed earlier, rather than a nightly opportunity to negotiate with myself for another episode.
Because sometimes, the best thing you can do for tomorrow's workout is get a little more sleep tonight.
Disclaimer
The information provided in this article is of a general nature only and is not intended to replace professional medical, health, or fitness advice. It does not take into account your individual objectives, physical condition, medical history, or needs. Before acting on any of the guidance or recommendations provided, you should consider whether it is appropriate for you in light of your personal circumstances. You should always seek the advice of a qualified healthcare professional (such as a physiotherapist, podiatrist, dietitian, or medical doctor) before starting, changing, or relying on any exercise, training, or nutrition program. Rebel Sport accepts no liability for any loss, injury, or damage suffered by any person relying on the information provided.
References
- Scott, H., Lechat, B., Guyett, A., Reynolds, A. C., Lovato, N., Naik, G., Appleton, S., Adams, R., Escourrou, P., Catcheside, P., & Eckert, D. J. (2023). Sleep irregularity is associated with hypertension: Findings from over 2 million nights with a large global population sample. Hypertension, 80(5), 1117–1126. https://doi.org/10.1161/HYPERTENSIONAHA.122.20513
