Slept for 7 or 8 hours but still exhausted? Work these 3 ‘sleep muscles’ for more energy, experts say

A good night's sleep doesn't just allow you to get through the day without yawning — consistent, good quality sleep can help you live longer, as a 2026 study from Vitality and The London School of Economics and Political Science (LSE) has found.

So how do we define a good night's sleep? For many of us, it's case of racking up enough hours. But the real marker for better sleep lies elsewhere: "Sleep quality matters just as much," explains Dr. Joshua Rolands, certified sleep doctor at Dreem Health.

Dr. Rolands notes that time spent falling asleep, nighttime awakenings, and sleep cycles all contribute to sleep quality. So if you want a good night's sleep, these are the metrics you should be looking for in your sleep tracker...

Key takeaways: At a glance

• If you're waking up tired after 8 hours it may be down to the quality of your sleep.
• Sleep quality is just as important as duration, and 3 key 'sleep muscles' can indicate the quality of your rest.
• The first sleep muscle is sleep latency; how long it takes you to fall asleep.
• The second sleep muscle is time spent in deep sleep; whether you're getting enough restorative rest.
• The third sleep muscle is sleep efficiency, how much time spent asleep when you're in bed (which is reduced by nighttime wake-ups).
• You can improve these 'sleep muscles' with simple steps including optimizing your sleep environment, creating a nighttime routine and sticking to a consistent sleep schedule.
• Consistent, good quality sleep can even add up to four years to your life, according to a recent study.

The 3 key 'sleep muscles' to focus on for good quality sleep

Dr Rolands says that these are key metrics for defining sleep quality: "How quickly you fall asleep, how often you wake up at night, how much time you spend in restorative stages like deep and REM sleep, and how refreshed you feel in the morning."

Here, we'll explore three of these key sleep metrics or 'muscles' and how they impact your sleep quality.

Muscle 1: Sleep latency

If you're regularly clocking up eight hours sleep a night, the time spent lying awake in bed at the start of the night might seem irrelevant to the overall picture of your sleep health.

However, increased sleep latency — when it regularly takes you over 20 minutes to fall asleep — can be a sign that your circadian rhythms are off track.

"Sleep onset latency is a sensitive indicator of how well the circadian rhythm is functioning," explains Ariel Garten, neuroscientist and co-founder of Muse Sleep Headband.

She notes that your sleep latency can "decline significantly" without a change in total sleep time. But as your circadian function is disrupted, you're probably not enjoying genuine recovery during the night.

Dr. Roland says this is the best way to reduce sleep onset latency: "Go to bed and wake up at the same time every day, even on weekends, to reinforce consistency.

"Regular exercise, exposure to natural light during the day, and avoiding long or late naps can also help you fall asleep faster," he explains.

Muscle 2: Time spent in deep sleep

Sleep trackers record how long you spend in key sleep stages: light, REM, and deep sleep.

During a healthy night's sleep, you cycle through each stage. However, when your sleep architecture is disrupted, you might spend most of the night stuck in lighter sleep.

"Your body relies on predictable, uninterrupted cycles to repair, regulate hormones, and support brain function," explains Dr. Roland.

Garten notes that deep sleep is when physical restoration happens, while REM is critical for emotional regulation and next-day cognitive performance.

"Small nightly losses in either compound into real fatigue and brain fog across the week in ways that total sleep time simply won't show you," says Gartner.

By the way, you need less deep sleep than you realize: for most adults, around 60 to 90 minutes of deep sleep a night is plenty.

Muscle 3: Sleep efficiency

Brief nighttime awakenings are normal; in fact, you might not even notice they happen. However, when you regularly wake up during the night, or when these 3 a.m. wake ups turn into 'middle insomnia', those long hours in bed aren't beneficial.

"Sleep efficiency – how consolidated and uninterrupted sleep actually is – tells you whether the time spent in bed is translating into genuine recovery," says Garten

"You can get eight hours of fragmented or irregular sleep and still feel exhausted," explains Dr. Rolands, "while consistent, high-quality sleep helps regulate your circadian rhythm, improving everything from mood to metabolism."

How to work these 3 'sleep muscles' harder for better energy

The good news is that you can improve your sleep quality and these 'sleep muscles' with some simple steps. We spoke to the experts to find out more...

1. Optimize your sleep environment

"To improve all three [muscles]," Dr. Roland first advises, "optimize your sleep environment."

This begins with a comfortable, sleep-supporting bedroom. Keep it cool (the best temperature for sleep is 65 to 70°F), and dark (light at night can disrupt your body clock) with the best mattress for your sleep style.

2. Create a nighttime routine

Alongside a bedroom that is conducive to sleep, Dr. Rolands says that it's important to "focus on building a steady bedtime routine," before bed in order to improve these sleep muscles.

"Create a wind-down routine that signals to your body it’s time to sleep, limit screens and caffeine in the evening," he suggests.

A wind-down, or nighttime routine, is a series of relaxing activities you do (or don't do, in the case of screens and caffeine) in the lead up to sleep, and can be anything you find calming; light yoga, reading, stretching, listening to music or perhaps sleep mediation.

3. Stick to a consistent sleep schedule

But the best way to stay on top of your sleep latency, deep sleep, and nighttime interruptions is with consistency.

"The circadian rhythm relies on regular sleep and wake times to stay aligned," says Garten.

When your schedule shifts, Garten notes your brain receives "weaker" sleep and wake signals. "This can gradually disrupt sleep architecture and reduce overall sleep quality."

The 60-minute bedtime rule recommends finding an anchor time and going to bed within a 30 minute time frame either side of this anchor. So if 10 p.m. is your anchor time, you'll be tucked up between 9.30 p.m. and 10.30 p.m.

In fact, this rule is based on findings from the Vitality study, where researchers discovered that going to bed within the same 1 hour window and getting at least 7 hours sleep a night (consistent, quality sleep) could add up to four years to your life.

However, "if you still are not resting well," adds Dr. Roland, "or have other sleep-related symptoms, such as snoring, pauses in breathing, or frequent movements, it is important you see a doctor to make sure you don’t have an underlying sleep condition such as obstructive sleep apnea."

Finally, pay attention to how you feel in the morning

As Dr. Reynolds mentions, feeling refreshed in the morning is a marker of whether you've had good quality sleep.

Garten explains more: "When the brain gets the recovery it needs overnight, the downstream effects are tangible: sustained focus, emotional resilience, and faster cognitive recovery,"

"That's the real measure of a good night's sleep."

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