[David70]

I don't see how many miles you are regularly running now. I am in a giant running group and too many sign up to do a marathon, then you find out they haven't run much ever or years. My opinion is they would be far better off training to do a half marathon now, then later do the full/50k, 6-12 months later. Too many of them increase their mileage too quickly and end up hurt, then likely giving up and saying they can't do a marathon because their body can't take it when reality is their body only couldn't take quick increase in mileage.

How soon is the 50k, how much running do you do now and have done in the last year?

Also add my body/back feel better when I do my long training runs on something other than concrete, prefer a trail and lots of stretching helps me overall.