I agree with this...In such a short period of time just be safe and try to get your body stronger and don't worry about running running running...because it could easily get you right back to square one. Like everyone said before streach, streach, then streach some more both before and after your runs. Make sure you are ultra warmed up before you hit it hard. As far as cross trainning I'd try climbing if you haven't already. Go to an indoor gym and just have at it. I go about three times a week and it is amazing how much of a complete body workout you get in such a short period of time. IMO it correlates well with the type of stuff that the PFT deals with i.e. push ups, pull up, sit ups etc. Its all about supporting your own weight. Plus there are always some hotties there, so that doesn't hurt. In anycase Good luck man!