I have primary progressive as well and as far as I have seen unfortunately they don't know what to do for us.  I was a runner, mountain biker and skier.  I was diagnosed when I was 28 but we didn't realize it was primary progressive until years later because the symptoms were so slow to progress.  I am now 41.  The best advice is continue to live your life to the fullest because you can't get these days back, eat a healthy diet, and stay active.  Once you start losing your muscles it is very difficult to regain.  I have tried every MS drug available but am now trying to do a more natural route and cleaning my body of all the drugs.