Ten minutes of running at three to six kilometres an hour. That is all. That was enough for participants in a study at the University of Tsukuba in Japan to feel better and to solve an attention test faster than before the run.

Three to six kilometres an hour is walking pace. The researchers deliberately did not ask anyone to finish exhausted or to beat their own time. They wanted to see what happens after short, easy activity - the kind most people dismiss as too small to count as exercise.

A test where the brain struggles

Participants ran on a treadmill at very low intensity for ten minutes. Before and after, they reported how they felt and took the Stroop test - a task where you have to respond to one piece of information while another pulls you away. For example, saying what colour a word is printed in while the word itself names a different colour.

After the run, participants solved the conflicting-information part of the test faster and reported a more pleasant mood. The researchers also noted increased activity in some zones of the prefrontal cortex - the part of the brain that engages when you need to hold attention without scattering it.

There is one detail that sounds like a joke but is not. The researchers measured the vertical movement of the head during the run and found that more bobbing was associated with a greater improvement in mood. What that means exactly - nobody knows yet, and it is not a technique worth imitating deliberately.

Health psychologist: you do not need an hour of punishment

"You don't need gruelling hour-long workouts to activate the mind and improve your emotional health," says health psychologist Hugo Fernández Robaina, who commented on the study. Brisk walking or very light running, in his view, can be a way to start moving without adding yet another heavy obligation.

He also recalls the official framework: the World Health Organization recommends adults get between 150 and 300 minutes of moderate physical activity a week. But if today you only have ten minutes, start there.

What the study does not say

It is worth being precise, because this is where findings like these usually get stretched beyond what they show. The experiment tested treadmill running, not walking. Whether brisk walking would produce the same effect was not compared. Activity in the prefrontal cortex is a sign of something, not an explanation of everything, and the researchers themselves do not claim to know why participants felt better.

What remains is still usable. Ten minutes stop looking "too little" when they break up an afternoon spent in a chair. Maybe you will want to keep going afterwards. Maybe that day you will only have that much. Either way, you found room to move without waiting for the perfect moment - and waiting for the perfect moment is the most expensive habit in this whole story.