… But, baby, we were born to run

Humans are hardwired through evolution to run – explaining the “runners’ high” after exercise, a study claims.

Our hunter-gatherer ancestors were long-distance athletes and may have evolved that way because of the high experienced at the end of a run, it is claimed in the Journal of Experimental Biology.

Professor David Raichlen, of the University of Arizona, said: “Aerobic activity has played a role in the evolution of lots of different systems in the human body, which may explain why aerobic exercise seems to be so good for us.

“We got interested in the brain as a way to look at whether evolution generated exercise behaviours in humans through motivation pathways.”

The “runners’ high” comes when natural chemicals called endocannabinoids activate the “reward centres” in the brain associated with feeling good.

The team trained dogs to run on a treadmill and collected blood samples before and after the exercise. They found the concentration of one endocannabinoid, anamide, rocketed in the blood of the dogs and humans after a brisk run. Human runners also reported feeling much happier after the exercise.

However, the blood of a lazier animal tested – the ferret – did not show increased levels of anamide after exercise.