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The 90-minute sleep cycle
Sleep research has shown that we go through the various light/deep/REM sleep states in a fairly consistent 90-minute cycle. This 90-minute pattern is closely linked to our circadian rhythms, our inbuilt body clock that naturally determines our wakefulness and sleepiness.
Importantly, our circadian rhythms respond best to a consistent sleep/wake routine. Indeed, your sleep quality has a lot more to do with following these natural rhythms and getting full 90-minute cycles than the overall duration of your sleep.
Also, the end of these 90-minute cycles corresponds to the periods of time when we are in our lightest sleep states, meaning we are more easily aroused and able to wake if needed.
Ever experienced a groggy and slow wake-up in the morning? You’ve likely woken up in the middle of a 90-minute sleep cycle.
How does this relate to training and exercise?
Quite simply, sleep is your most powerful recovery tool: High-quality sleep = high-quality recovery. Conversely, poor quality sleep = impaired recovery.
By understanding these concepts, you can improve the quality of your sleep to enhance your training recovery by ‘planning’ your nightly sleep around these 90-minute cycles, giving you a lot more flexibility than simply aiming for the stock standard recommendation of 8 hours.
When we hit the hay each night, our bodies go through the various light/deep/REM sleep states in a fairly consistent 90-minute cycle.
Why Have Such Flexible Sleep?
The standard ideology of ‘8-hours sleep per night for maximum recovery’ is simply too rigid for our busy modern lives. If your 8-hours normally runs from 11pm-7am, what happens if you want to stay out at a function or are travelling and can’t get to bed by 11pm? What happens if you have appointments that will require you to get up before 7am? Planning sleep in 90-minute cycles around such commitments is an incredibly flexible and practical solution.
How To Cycle Your Sleep
1. Plan your nightly sleep in 90-minute cycles & aim for 5 cycles per night
Follow this formula and you’ll be hitting a nice 7.5 hours each night. If you have to wake-up earlier than planned, wake-up at the start of the 90-minute closest to your required wake-up time e.g. If I need to be up for work at 5:30am and I normally wake at 6:30am, then I’ll get up 90-minutes earlier than normal at 5am – this time corresponds with the end of that sleep cycle. Whilst that may sound a little crazy, remember waking up at the end of a 90-minute sleep cycle is the best way to not feel groggy and slow.
If you need to go to bed later than normal, go to bed at the start of your next 90-minute cycle e.g. If you can’t make your normal bedtime of 11pm, go to bed at 12:30am – this time aligns with the start of your next sleep cycle. Again, this gives you the flexibility to go to bed around life’s commitments, but still get a quality sleep because you’re sticking to your natural circadian sleep rhythms.
2. Always get up at the same time every day regardless of how many cycles you have
For example, I always get up at 6:30am and aim to be asleep by 11pm (7.5 hours = 5 cycles). Once again, your body’s energy levels are determined largely by your circadian rhythms, which thrive on consistent routine and take a hit when you constantly change your sleep-wake schedule. If you want to ‘sleep-in’ without interfering with your body clock, stick to your normal wake-up time, get up for at least 15-minutes and be active, then go back to bed for the sleep-in.
3. Aim for 28-35 sleep cycles each week
McPartland, R. and Kupfer, D., 1978. Rapid eye movement sleep cycle, clock time and sleep onset. Electroencephalography and Clinical Neurophysiology, [online] 45(2), pp.178-185. Available at:Rapid eye movement sleep cycle, clock time and sleep onset..