I used to run quite a bit. I was as fit as they come when I was in the forces. When I left I didn't really do much running, mostly football now keeps me fit. Similar story to a couple on here, but a lad I worked with was a very keen runner. Used to do fell running and all that. He went away to feurtaventura to do a marathon and dropped down dead in the first 4 miles. Scary stuff.