The Power of 90 (to 120) Minutes

Updated: Mar 12, 2021

When you work with, rather than against, your natural rhythms you have the capability to maximise your productivity and effectiveness and enhance your wellbeing.

Tap into what nature gave you and sleep, work, rest, repeat. Try it for 90 to 120 days – see what happens!


I saw a quote on social media recently which said something along the lines of ‘don’t stop when you’re tired, stop when you’re done’.

The ignorance and irresponsibility in this, and similar statements…….. well, gets my hackles up!

What it does exemplify is a social norm where busy is idealised and resting and sleep, at best, are seen as a luxury. Something you get to do after the ‘to-do’ list is finished, or for those amongst us who are not interested in being one of life’s achievers.

As human beings we are not designed to run non-stop. Whilst we might instinctively know this, we can easily get sucked into trying to push through to get it all done.

But this approach cannot work. Not only does it work to your detriment health wise, it also works to your detriment in terms of productivity and effectiveness, and there is a good reason for this.

To function non-stop, without adequate rest and sleep, means you have to go against how nature intended human beings to function. Against your natural rhythms of which you have two – a Circadian Rhythm and an Ultradian Rhythm.

The Circadian Rhythm

You may have heard of the Circadian Rhythm which basically governs your sleep/wake cycle, over roughly a 24-hour period.

As human beings we have about 16 hours of waking battery life, before needing about 8 hours of sleep to recharge fully overnight.

But outside of that we each operate slightly differently. For instance, some of us are morning folk and others night owls. Some of us like to eat early and others late. These and similar functions are also determined by your Circadian Rhythm.

The Ultradian Rhythm

Nathaniel Kleitman, one of the early sleep researches, discovered that we operate in 90 to 120-minute cycles. Kleitman called these “basic rest-activity cycles’ but they have come to be known as Ultradian Rhythmswhich work alongside Circadian Rhythms.

Throughout the day, this rhythm moves you naturally between high and low energy.

During the ‘high’ your brain is working in a high frequency pattern where it chews up more resources, so it makes sense that you can’t sustain it for too long. Yep you guessed it – approximately 90 to 120 minutes.

After this time, the brain activity will want to shift gears and have a break. It apparently takes about 20 minutes before you are allocated the next burst of energy.

If a sound night’s sleep gives you a fully charged battery to play with in the day, the ultradian rhythm essentially ensures you don’t expend it all at once.

If you ignore this call to rest, you are likely to feel a bit fatigued and your concentration is likely to wane. Obviously, this is going to have an impact on your productivity and effectiveness.

Continue to ignore it, and your body is likely to kick off the stress response to put you in a heightened state to get you through a perceived threat. From evolutions perspective, why else would you continue to work past the point of healthy if you weren’t in danger?

Whist the stress response has it’s uses, it won’t result in you getting any more done, as you are likely to lose contact with your higher brain function. All you need to do when in danger is ‘fight or flight’ right?

So ‘don’t stop when you’re tired, stop when you are done’ is not only stupid, it is also futile.

Working with your own rhythms

Approximately every 90 to 120 minutes during the day, your body is going through a period of high energy and alertness, followed by a period of tiredness and fatigue - fact.

The theory is that if you tap into this, you will be able to use your highs to get more done and your lows to rest - so you are working with, and not against, your natural rhythms.

Ideally, we should not be competing with our own bodies and tuning in to our own ultradian rhythm. Working in 90 to120-minute bursts without distraction, and then responding to the call to rest, knowing that we will come back recharged and able to work once more at our optimal best.

I’ve heard it said than when you plan, prioritise and work in this way that you can increase your productivity by 400%. I am unaware of any known percentage increase to your health, but would envisage this to be significant.

Whilst tapping into the ebbs and flows of your energy makes evolutionary sense, it’s not exactly easy to do in today’s society.

Whilst education on this subject is key, I’m going to share with you some ideas on how you might go about building in more rest. How you might go under the radar, if need be, to get the rest you need, so you can get more done and look after yourself along the way.

Sleep Precious Sleep

The National Sleep Foundation and Centre for Disease Control and Prevention recommends that all adults should be getting 7 to 9 hours of sleep opportunity (time in bed) each night.

However, for many people sleep is a challenge, or also perceived as a luxury. Something that is easily deprioritized in favor of a busy schedule or saved up for weekends. But again, not prioritizing sleep is going to work against nature and negatively impact your wellbeing and effectiveness.

Kleitman discovered that we sleep in 90 to 120-minute cycles, prior to identifying this pattern during waking hours. He was after all a sleep researcher.

During each sleep cycle, you alternate between Non-Rapid Eye Movement (NREM) and Rapid Eye Movement (REM) with each cycle lasting between approximately 90 and 120 minutes.

The cycle repeats around 3-5 times a night with more NREM experienced earlier in the night and more REM later in the night. If you go to bed late you will short change yourself on the amount of NREM you get. Equally if you get up too early you will short change yourself on the amount of REM sleep you get.

Both NREM and REM come with dramatic benefits to mental and physical wellbeing, and effectiveness, and both are equally important.

Following a good night’s sleep, we awaken with a healthier body and a revised mind, ready to face the day with optimal reserves in the tank.

Non-Rapid Eye Movement (NREM)

NREM occurs in 3 (previously 4) stages and is often referred to as the deep sleep state. Here is where you experience your deepest sleep, and where a lot of body’s rest and recovery takes place.

This phase of the sleep cycle is also when the information experienced in your waking life is effectively sorted through and either deleted or saved. When your experiences are taken from the temporary storage of the hippocampus to the longer-term storage of the cortex.

In this way, NREM can be seen as the part of the sleep cycle that helps to cement knowledge and learning, and strengthen individual memories. Rather like storing files on a computer system.

Rapid Eye Movement (REM)

Often referred to as the dream state as this is when most of your dreaming is done.

During sleep, a part of the brain called the thalamus shuts off the senses from external stimuli, so you don’t get woken up by every minor distraction. Whilst during REM this is still the case, the thalamus opens up to internal stimuli from thoughts, memories and emotions. You may experience this as dreams, during which time your muscles lose their tone and the body is paralyzed to prevent you from acting out your dreams.

Key emotional and memory structures are activated during REM, and a chemical called noradrenaline (similar to adrenaline but for the brain) is shut off. This is believed to be the only time, during the day or night, when the brain is void of this anxiety triggering molecule. This could indicate that whilst you sleep you are able to process challenging and emotionally charged experiences without the stress.

Along with helping you to process emotions, your brain will sieve through vast amounts of acquired knowledge during the dream sleep state, extracting overarching rules and commonalities.

REM is what allows you to intelligently link the knowledge stored from NREM in the mind’s filing system. It allows you to move from knowledge to comprehension

Hi ho, hi ho it’s off to rest we go

Managing energy by taking advantage of what nature gave us is the secret to maximising effectiveness and optimising wellbeing.

Whilst the Circadian Rhythm and Ultradian Rhythm are not directly linked, if you do not get enough sleep you are likely to get more energy dips during the day. So, sleep must be seen as a necessity, the origin for getting your daily energy quota.

Once you have a fully charged battery, resting must be incorporated into your day so you become efficient in how you utilise it.

Here are some techniques for you to consider to incorporate more rest whilst you work:

1. Take a break – seriously!

Many organisations used to have a policy of a morning, lunch and afternoon breaks. Some still do. Makes perfect sense doesn’t it? You work for 90 to 120-minutes, take a break and then continue.

But even if the option is there and encouraged, how many employees are actually taking them?

Instead employees opt to sit, drink and eat on the job whilst ploughing through, in a hope of getting more done.

I hear this story far too often knowing, only too well, that it can’t and doesn’t work and is likely to lead many down the path of diminishing health, stress and burnout.

Building in your own, or prioritising taking, a morning, lunch and afternoon break will mimic the highs and lows of the Ultradian Rhythm, and over time you may be able to line these up with your own highs and lows.

Hopefully by now you will be convinced that it is worth it.

If you are an Organisation reading this, who wants to increase effectiveness whilst supporting the health of your workforce, teach your employees the power of 90 to 120-minutes and considering making it a KPI to take breaks.

Truck drivers have to take a break after 4 hours, as it is not safe for them to be on the road longer than this.

Employees need to take regular breaks during the day as it is not safe for them to work continuously, nor does it make sense from a productivity perspective.

2. Use Productivity Techniques

In a sense the reverse of this is to work with productivity techniques which have been proven to result in getting more done.

These are a great way of getting in the habit of consciously planning and assessing tasks, focussing on one thing at a time, and then having a rest.

The Pomodoro Technique

Devised by Francisco Cirillo in the late 1980’s, the Pomodoro Technique is fantastic for breaking down work into intervals, traditionally 25 minutes separated by short breaks. It goes something like this:

  1. Choose a task to work on

  2. Set a timer for 25 minutes

  3. Work intensively until timer sounds

  4. Take a 5-minute break

  5. Continue with steps 2 – 4 until you have completed 3-4 cycles

  6. Then take a well-earned 20-minute break (or more)

  7. Assess how well it went so, if required, you can make any improvements in terms of managing your focus, minimising distractions etc

Work for 52 minutes and break for 17 minutes

Okay so this isn’t strictly working in 90 to 120-minute cycles. The concept comes from a company called DeskTime, who have an app that can track computer usage. From the data gathered they discovered that the top 10% of productive workers took, on average, a 17-minute break after working for 52-minutes

Whilst these timings are pretty specific it is not that dissimilar in concept: work, rest, repeat to get more done.

Overall the moral of the productivity story is that in order to become more effective and productive you need to rest and recharge in between controlled bursts of activity. Ultradian Rhythm anyone?

3. Shift your attention

If you are working on something that is chewing up your energy, have a mental break by shifting your attention to something that is light hearted and less demanding. Something that doesn’t require you to be using your high frequency brain activity and chew up your battery charge.

If applicable and possible, shift from sitting to standing or standing to sitting whilst you are doing it to, give your body a break too.

4. Move

Resting doesn’t necessarily mean you need to be sedentary.

Getting some exercise by perhaps going for a walk, preferably outside so you get some fresh air. Or if that isn’t possible, have a walk around your workplace or home.

Alternatively, have a stretch – here are a few stretches for office workers.

Often, we get to the end of the day and feel the effects of the job – usually too much sitting or too much standing.

Awareness of these may not occur during the day, as pain receptors can switch off when you are busy or stressed.

Left unmanaged, this may result in the muscular and skeletal system adapting over time or potentially lead to injury.

Taking a few proactive measures, like interrupting your sitting or standing and moving, can go a long way in preventing or alleviating physical symptoms and downstream issues.

5. Have a Desk Vacation

Take a mini vacation whilst at your desk.

Stop what you are doing and if you are unable to leave your desk, have a desk vacation - perhaps incorporating:

1. A mindfulness technique or meditation

2. Pop your ear phones in and listen to some, relaxing or uplifting, music

3. A Breathing Practice

4. Progressively work your way through your body, relaxing your muscles by tensing and

releasing them. Start at your feet and progress to your legs, glutes, torso, arms, hands,

shoulders and your face. A great way to let the tension out.

5. Doodleto shift your thinking whilst perhaps coming up with some new ideas.

6. Talk to a colleague, friend or professional to get support, if you need it, or simply to

temporarily shift your attention.

7. Check out some photos of when you were on vacation or have a daydream about the

next one.


Tap into what nature gave you and sleep, work, rest, repeat. When you work with, rather than against, your natural rhythms you have the capability to maximise your productivity and effectiveness and enhance your wellbeing. Try it for 90 to 120 days – see what happens!

This blog was written for Cytoplan and is also available on their website:


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