Hi there,
I started running this past spring, so I can offer you a little advice. First off I do NOT have CF but my 3 1/2 year old daughter does. Running has been very therapeutic for me, relieving stress and frustration.
A couple tips: Hydration is key. I take a sports water bottle with me for longer runs, I would consider 6 miles a long run. There is also something called a camelback, it's like a backpack with a bladder whcih you can fill with water or sportdrink(like Gatorade). if you have problems with blood sugar , you could always just put a little salt in you water or take salt tablets.
Just take it slow, you could jog 2 miles and walk briskly one for starters. You probobly know your body best, so if you need to slow dwon listen to your body. I would also let your doc know about your exersize plan, they could help you with nutrition.
I also invested in a book about running, has lots of tips for training.
A few things I've learned are be very careful running if you feel you are coming down with something like a cold. you don't want to overdo it. Overtraining through a cold can lead to upper resp infection. this happened to me last winter and I ended up on antibiotics.(Again i do not have CF).
Make sure you get plenty of rest, no alchoholic beverages(very dehydrating). Plan on eating about 2 hours before a run so you digest your food and don't get a cramp. And like I said if you feel your body telling you to slow down , then slow down.
I'ld be happy to provide more tips if you need to, the mom in me says tell your Cf doc of your plan in terms of running in case he/she has concerns.
Anyhow, running has helped me cope with the day to day care of my daughter. I feel it has defiantely inproved my heart and lung function.
Good luck,
Rebecca( mom to Sammy 8 no CF and Maggie 3 1/2 with CF)