A quiet day at work so I thought I would add my pennyworth to the whole 'running is addictive' debate. You may recall that Pavlov had some dogs. He rang a bell and gave the dogs some food, After a time, the dogs salivated whenever they heard the bell. They were conditioned through a process of reinforcement.
Now, intermittent reinforcement is the most powerful means of conditioning. If you go to the pub and put your money in the jukebox, you will quickly notice if it is broken and stop wasting your cash. If the one armed bandit is broken, you will keep piling your pennies in for much longer because it operates on an intermittent reinforcement schedule- It doesn't pay out every time.
So to running. Some good runs; runs where you are running the dream. These are interspersed with runs that are less great and some that are painful or hard. So you are being reinforced on an intermittent basis; always chasing the positive, reinforcing feeling. Running doesn't pay out every time either. You are conditioned to want to run.
Now, it's really important to keep running in a routine.... Eventually, the gambler will notice that the bandit is not paying out and will stop feeding it. Their behaviour has been extinguished. If you don't run enough, you will miss the positive reinforcement and you are at risk of your running behaviour being extinguished also.
And now my dog is making the little noises that suggest it is time for his walk. He has conditioned me and I have to go now