Runners World has a great interview with Bear Grylls on their site from their May 2011 edition.
Occupation: Host of Man vs. Wild
Residence: Abersoch, U.K.
How did you get started running?
In the military. In the British Special Air Service, combat fitness is all about running. We would go until we ended up vomiting on the side of the road. Once I left the military, I gave up running for a while. It took me a while to realize it doesn't have to be like that. Running can be a great therapeutic way of training. These days I push myself hard, but I also slow down and take it easy sometimes. It doesn't have to be full-on hard all the time.
When did you get back into running?
After the military, I spent a year being really unhealthy, not exercising. I got back into running when I was offered my first commercial [for Degree deodorant]. I thought, If I'm going to have to take my shirt off, I'd better start doing sit-ups and start running.
Later, I got my first TV series [Escape to the Legion], which was about basic training for the French Foreign Legion out in the desert of North Africa. During that time, running was a part of everyday life. We were running two or three times a day. We always had to wear these terrible thin-soled pumps [sneakers]. We had horrific blisters. I just remember these blood-soaked white pumps [sneakers].
Check out the rest of the interview over at Runners World.