My 10 mile race

So I will be running a 10 mile race on Saturday week, as part of the adidas Dublin Race Series 2008 . I done a 5 mile there a few weeks ago and done it in 45 mins, which wasnt too bad for a first go. I am going to really challenge myself and try and do the 10 mile under 1hr 25mins, which will be pretty tough! After that is the half marthon, and after that is the marathon - I am not sure about doing the marathon, the time committment in terms of training might be just that too much, particuarly as I finish my PhD.