Why we love to run

It's tough, it hurts – and yet more than two million of us in the UK run at least once a week. Why? To launch our new running blog, Adharanand Finn explains the enormous pleasure it brings – and how we're actually hardwired to do it

"Daddy, where are you going?" my son asked me recently as I was lacing up my running shoes on a cold, wet Sunday morning. "Running," I said. "Why?" he asked.

He's only three. But it was a good question, and one I couldn't readily answer. I didn't really want to go....