I've started to taper off running and concetrate more on building up my muscles for strength. My reasoning for this is on the trail you are not running over distances you are carrying weight, sometimes lots of it up and down hills. The more you can do the easier it will be carry loads up the steep grades. Running doesn't provide the muscles for this, strength training does. Also running puts alot of shock energy on the knee joints which can be very painful if it starts to wear ligaments down. Of course your heart needs to be strong and efficient to carry blood to these muscles which is where cardio comes in. I plan on doing the elliptical and stair stepping machine more because this is less impact on the knees while relatively giving you the same workout. I'm not going to stop running completely, just less now.

STRETCH STRETCH STRETCH!!!! Flexibility is more important than anything early on. I regularly lift weights and stretch as part of my work out routine and it has made a world of difference in my hiking. Much more important than cardio work....after all in the end you are just walking, you'll get your lungs on the trail no matter what...muscle and loose tendons/ligaments...that's another story entirely.

Check this out:
http://www.whiteblaze.net/forum/showthread.php?p=184425#post184425

Good stuff!

I found that core and strength work out greatly improved my stamina, balance and enjoyment of my section hiking. I doubt there is anything one can do to prepare for true thru hiking, but how could physical preparation be a problem?

I've started to taper off running and "concetrate" more on building

What is doing "CONCETRATE"..??..LOL........