Hi again Rhet,
right ok, to answer some things:
1) Greater mucus clearance
2) Temporary increase or delayed decline in some indices of pulmonary function.
1) This is because the most you excercise the heavier and deeper you will be breathing. This will be bringing with it mucous from deep down in the lungs. This will be much better for your lungs and leads to increased lung function, and less infections.
2) As you are excercising, and bringing up all the gunk from deep down, it is leaving behind a bigger breathing space. So you will have an increase in lung function. This may however not stay, because you will still be getting infections, which still cause damage. But I guess you will have a slower rate of damage.
When a person with CF is new to excercise, a monitor should be available for saturated oxygen and heartrate levels. This is because in CF the heart compensates for low lung function. Some people with CF, may be at resting with a 110 heart rate, so could be looking at levels of 160-180 as when they really have to stop and rest. Same with spo2 some may find they have a normal of 99, but desaturate quickly, others may have a normal level of 93, but hardley ever desaturate. Doing excercise in short bursts when you get started, until you notice either level is getting too high or low is probably the best way to go to building up a tolerance to excercise. You can always have another short session later in the day, if you're not too tired.
Jess really does have the best spirit too keep her well. :)
Hope this helps