When he ran the four-minute mile in 1954, Sir Roger Bannister said, "No longer conscious of my movement, I discovered a new unity with nature. I had found a new source of power and beauty, a source I never dreamt existed."

Bannister was describing "flow", a unique state of mind when we're so absorbed in an activity that we lose all track of time and effort and feel intensely fulfilled. The term "flow" was first coined two decades after Bannister's experience, by psychologist Mihaly Csikszentmihalyi .

Flow, a state of optimal experience, arises in a very specific setting. You need to be doing an activity that embraces your skill set with a series of challenges you're able to overcome only by stretching yourself. You feel good when you conquer each challenge. You're neither overwhelmed by its difficulty nor bored.

If the challenge is repetitive, its difficulty increases to match your improvement so you continue to stretch your skills and get incrementally better. The activity provides continuous feedback so you're reassured of your successful progress as you grow.

Not only is flow associated with optimal performance, but people who regularly experience flow are happier and seem less stressed than those who don't.  

Relax while being productive.

Flow holds intrigue because it flouts some rules. People can keep going for a long time without experiencing cognitive fatigue, despite being cognitively engaged. They also report feeling calm and detached from negative emotions, a state that is usually associated with deep relaxation, not with cognitive engagement in an activity.

When the concept of flow was first coined by Csikszentmihalyi, we knew its subjective experience but not its objective mechanism. We weren't able to look inside the brain to see what happens during flow that explains these apparent paradoxes. 

Today, almost half a century after Csikszentmihalyi first introduced the idea of flow, sophisticated MRI brain scanning techniques are providing some answers.

What does flow look like in the brain?

In a recent study from the University of Ulm in Germany, twenty-three healthy volunteers had their brains scanned under three conditions: boredom, cognitive overload and flow.

The flow state was achieved by giving volunteers arithmetic problems that perfectly matched their ability. In the cognitive overload setting, the problems were three times as difficult while those who were bored were given problems they found too easy.

The volunteers experienced more sympathetic activity in flow than in cognitive overload, even though their challenge was easier. They also had demonstrably less activity in the amygdala, a brain region involved in emotion-processing, as well as in a network known as the default mode network, which is active when we're thinking about things relating to ourselves.

Work with your brain, not against it.

The state of flow is associated with a distinctly unusual pattern of brain activity.

At the start of a stress response, your autonomic or "automatic" nerve network increases sympathetic activity, which makes you more alert and mentally sharp. This sympathetic arousal helps to trigger the stress hormone cascade, which encourages emotional reactivity. 

In flow, there is a rise in sympathetic activity with a paradoxical fall in emotional reactivity, meaning you're mentally sharp and alert while being emotionally calm, at the same time. 

This state of heightened mental alertness without negative emotional contagion is the holy grail of optimal performance, one that even manufacturers of smart drugs such as Modafinil and L-Theanine tend to aim for. 

When you're in flow, the lever for optimal performance is pushed by the brain without external help. Rather than forcing it to perform with a pill, you're leading it to an activity it likes and knows it is good at, so it wants to perform optimally by itself.

What this means for you

If your mind is overwhelmed  with negative thoughts, then getting into flow can help you detach and put a lid on your emotional reactivity.

To get into flow, find an activity incorporating a series of challenges you're able to overcome with effort. Each challenge should just meet your skill set, without making you feel anxious or bored. You should be receiving constant feedback on progress. 

Operating surgeons experience flow when each step in an operation is a challenge. Runners experience flow when they meet the challenge of making progress along their track.

If you can't incorporate flow into your work, smartphone games such as Tetris may be a good option during breaks when you don't want your mind to wander. Once you've immersed yourself for long enough to uncouple your mind from negativity, you can face the real world again with perfect self-control.