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We’ve quite quickly gone from ‘Yeah, I slept alright’ to analysing readiness scores before we’ve even had our morning coffee, or matcha in my case!
Between wearables, sleep apps and recovery dashboards, we’re now swimming in data. Devices like the Oura ring promise to tell us how well we slept, how recovered we are, and whether we should train, rest or hide under a blanket.
But what do these numbers actually mean? And is eight hours really the holy grail?
Let’s decode it properly.
Why Sleep Is Such a Big Deal
Sleep isn’t passive - it’s not just ‘switching off’. It’s when your body repairs muscle and tissue, balances hormones, regulates blood sugar, strengthens the immune system and clears metabolic waste from the brain. Deep sleep is particularly important for physical restoration, while REM sleep supports memory, learning and emotional processing.
When sleep is consistently poor, everything else feels harder. Blood sugar becomes wobblier, cravings creep in, stress tolerance shrinks, training recovery dips, and mood feels more fragile. From a health perspective, sleep is foundational - it underpins almost every other input.
But the crucial thing to understand is this: quality trumps quantity.
The Key Metrics That Actually Matter
You don’t need to obsess over every possible metric. A few core markers tell you most of what you need to know.
Heart Rate Variability (HRV)
HRV is one of the most useful recovery markers we have access to at home.
It measures the tiny variations in time between each heartbeat. Counterintuitively, more variability is actually a good thing. A healthy nervous system isn’t rigid; it adapts moment to moment. Higher HRV generally suggests your parasympathetic ‘rest and digest’ system is doing its job. Lower HRV reflects a high stress load (emotional, physical, immune related and environmental).
That stress might be obvious - work pressure, poor sleep, hard training, lots of travel - or more subtle, like undereating, alcohol, inflammation, lack of social connection, or illness brewing. Either way, you can check my free pdf for my 6 stress firebreakers here, and pepper these in through the day.
What matters most isn’t the number itself, but your trend. Your HRV is individual. Comparing it to someone else’s is pointless. If yours drops noticeably for several days in a row, that’s useful feedback that your system may need more recovery. Also do note that HRV naturally falls as we age so make sure you are plotting against averages for your age group if looking for general guidelines on what to be aiming for!
Resting Heart Rate (Especially Your Lowest Night-Time Value)
Your resting heart rate during sleep tells a complementary story.
Ideally, heart rate drops fairly early after you fall asleep. That suggests your body has shifted smoothly into recovery mode. If it stays elevated for hours, something may be keeping your system slightly activated. Common culprits are late heavy meals, alcohol, intense evening exercise, overheating, or simply not properly winding down. Yep, you scrolling in bed will be noted in your RHR reading….!!
If your lowest heart rate doesn’t occur until the early morning, that can suggest your body struggled to fully relax until late in the night. It’s often a useful clue that something in your evening routine needs adjusting.
Sleep Stages (Deep and REM)
Wearables estimate sleep stages rather than directly measuring brain waves, so don’t get hung up on exact minutes. Instead, look for patterns.
Deep sleep is associated with physical repair and tends to improve when stress is managed, alcohol is limited, and blood sugar is stable. This tends to concentrate towards the beginning of the night.
REM sleep supports emotional processing and cognitive function, and can be drastically reduced by chronic stress, hormonal shifts and fragmented sleep. Especially if you wake early as this concentrates towards the end of your night’s sleep which is why many people often feel very mentally or emotionally fatigued if they frequently wake early as opposed to struggling to fall asleep. Alcohol and blue light from screens are the biggest enemies of REM sleep so I’d look at those if you’re struggling with this.
Do We Really Need Eight Hours?
Eight hours has become the gold standard, but it’s actually an average, not a rule.
Sleep needs vary depending on genetics, age, stress load, hormonal status, training intensity and overall health. And of course how effective their sleep cycle is. Some people genuinely function beautifully on six and a half to seven hours. Others need eight and a half. There isn’t a single magic number.
What matters far more is how restorative that sleep was.
Six hours of deep, consolidated, high-quality sleep can leave you far more recovered than eight hours of broken, shallow sleep. A longer time in bed does not automatically equal better recovery.
In fact, spending excessive time in bed (especially if you’re bringing work or brain stimulating things with you) will fragment sleep and reduce sleep pressure the following night. More isn’t always better.
The better question to ask is: do you wake feeling restored? Is your energy steady? Is your mood resilient? Are your recovery metrics broadly stable?
That tells you far more than chasing an arbitrary hourly target.
How to Actually Improve Sleep Quality
The solution usually lies in fairly simple fundamentals.
Finishing heavier meals two to three hours before bed can make a noticeable difference, as digestion keeps heart rate elevated and competes with overnight recovery. Alcohol is another common disruptor; although it may make you feel sleepy initially, it suppresses REM sleep, raises heart rate and lowers HRV, often quite dramatically.
Creating a genuine wind-down period is equally important. Your nervous system cannot jump straight from emails, scrolling or intense television into deep restorative sleep. Lower lighting in the evening, gentle stretching, reading something calming, or practising slower breathing with a longer exhale can all help shift the body into a parasympathetic state. Feel free to check out my free Evening Wind-Down pdf here.
Morning and evening light exposure is one of the most underrated tools. Getting outside within the first hour of waking (even on a grey British morning!) and then doing the same as the sun goes down helps anchor your circadian rhythm so melatonin is released more effectively at night.
Regular movement also supports deeper sleep over time, althoughI would clarify that higher intensity sessions and cardio are best done earlier in the day as if you do them later they’ll keep your heart rate high and your body in ‘go’ mode when its time to go to bed.
And perhaps most importantly, if you are tracking your sleep please don’t let the data create stress. There’s even a term now - orthosomnia - for becoming so fixated on achieving perfect sleep metrics that sleep actually worsens. Any wearable is there to inform you, not judge you. Don’t check your sleep metrics until lunchtime is a golden rule I give my clients and also live by myself.
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