It's long been known that running is great for the body but now there is mounting evidence it's good for the brain too.
Scientists believe pounding the treadmill releases proteins which can help improve memory and boost brain cell growth.
Now researchers have found a new compound which can be directly traced from the muscle to the brain called cathepsin B.
They discovered levels of the proteins increase after someone goes for a run.
Doctor Henriette van Praag, a neuroscientist at the National Institute on Ageing in the United States, screened for proteins which could be secreted by muscle tissue and transported to the brain.
She and her team conducted a series of experiments on mice to test the memories of those lacking the protein compared to normal mice.
Over the course of a week, both groups were given a daily swim test in a water maze.
The animal is placed in a small pool ad must learn to swim to a platform that is hidden just below the surface of the water.
After doing the task for a few days, those with normal levels of the protein eventually learn where to find the platform.
However, when both groups ran before their daily swim test, the normal mice were better able to recall the location of the platform.
But those unable to make cathepsin B could not remember its location.
Dr van Praag said the team the findings were important as it was the first time this had been tested.
'Nobody has shown before cathepsin B's effect on spatial learning,' she said.
'Moreover, in humans who exercise consistently for four months, better performance on complex recall tasks, such as drawing from memory, is correlated with increased cathepsin B levels.'
She added: 'Overall, the message is that a consistently healthy lifestyle pays off.
'People often ask us, how long do you have to exercise, how many hours? The study supports that the more substantial changes occur with the maintenance of a long-term exercise regimen.'
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