We all want to be our best, most productive selves at work, which is why there are so many productivity hacks and methods out there to help us get the most out of our time. Recently, we’ve seen everything from ‘chore snacking’ to the pickle jar technique heralded as ways to boost our focus and concentration and get more done.

Now, it’s the 90/20 rule making waves. An approach to productivity aimed to help the brain work at its best, the 90/20 rule involves working in 90-minute cycles followed by a 20-minute break. You might have heard of something similar called the Pomodoro technique (where you work for 25 minutes followed by a five-minute break) but the 90/20 rule is designed to fit with how your brain works. 

The idea is that the brain uses up most of its energy source (glucose) and ability to concentrate in those 90 minutes, so taking a 20-minute break allows it to recharge. That way, you’re not forcing yourself to work when your brain isn’t at its best. 

But is this really true? Does the brain work in 90-minute cycles? And if so, is simply downing tools and not working for a bit enough to help it rest and recharge? 

To find out more, we asked Dr Steve Allder, consultant neurologist at Re:Cognition Health, to weigh in on the 90/20 method and explain how we can work with our brains to optimise our ability to focus and concentrate at work.  

While the basis of the 90/20 rule – ie that the brain uses up most of its energy within 90 minutes – might sound legitimate, Dr Allder says the science is a little more complicated than that.

First things first, the brain doesn’t just rely on glucose to help us concentrate at work – it’s constantly using it. “The brain doesn’t completely use up most of its glucose every 60-90 minutes, but it does consume glucose continuously due to its high energy demands,” he explains. “The brain accounts for about 20% of the body’s total glucose consumption despite only representing 2% of body weight.”

In this way, the brain will continue to consume glucose whether you’re concentrating at work or watching your favourite TV show. However, the former may speed up the rate of consumption because your cognitive activity levels will be elevated, meaning your brain requires more fuel. 

So, where does the thinking behind the 90/20 method come from? Dr Allder suggests it’s got something to do with one of the brain’s ultradian rhythms – a term used to describe a biological cycle under 24 hours in length. 

The ultradian rhythm that relates to the 90/20 method is the basic rest and activity cycle, which sees the brain fluctuate between periods of wakefulness and rest. When the brain is working well, we’ll typically have 90 minutes of wakefulness (during which our brain is activated and better able to focus) followed by 20 minutes of downtime. By tuning into this rhythm and giving our brains regular breaks – as we do using the 90/20 method – the brain may be better able to perform. 

As well as using up glucose at a faster rate, trying to ‘push through’ these periods of rest can lead to your brain becoming tired and depleted, which can have a knock-on effect on your whole body.

“When glucose levels in the brain drop, mental fatigue sets in, resulting in reduced cognitive functions like memory, focus and decision-making,” Dr Allder explains. “This depletion can make it difficult to concentrate or perform complex tasks; if the brain lacks glucose, it may signal to the body that it needs more fuel, which can lead to feelings of hunger, irritability or a general decline in energy and alertness.”

On the flipside, taking time away from your desk to give your brain a chance to recuperate can make a big difference to your ability to concentrate. “Taking a break can help the brain recover and regain focus,” Dr Allder adds. “Short breaks where you deliberately defocus the brain for around 10–30 minutes, especially after intensive cognitive work, allow the brain to relax and restore energy levels. This can improve mental clarity, prevent burnout and enhance productivity.”

He continues: “Activities like stretching, walking or engaging in light, non-cognitive tasks (ie not on a smartphone) can help boost blood flow, restore glucose levels and reduce mental fatigue.”

Working with our brains can not only stop us feeling tired and agitated, it can boost our productivity levels and help us enjoy work more. But not all of us can take a 20-minute break every 90 minutes. So, what else can we do to help our brains work well?

“To boost productivity and focus, it’s essential to maintain a balance between work and breaks, adopt healthy habits and nourish the brain,” Dr Allder explains. “Regular physical activity, sufficient hydration and eating brain-boosting foods such as nuts, whole grains and leafy greens can provide steady energy.

“Using techniques like time-blocking or the Pomodoro method (working for short bursts with breaks) can enhance focus. Additionally, reducing distractions and practising mindfulness can improve sustained concentration.” 

Images: Getty