I'm thinking of signing up to a Santa Fun Run near me - I am pretty fit at the moment and can run for about 20mins moderately (the treadmill says this is 7/8km per hour). I've heard that running outside is much more hardwork due to the terrain etc. I do quite a lot of strengthening classes and dance at my gym, but don't run every day. Has anyone got any advice for a training plan? Thanks very much.