I was first advised to only reduce my basal by 30% whilst exercising..
That didn't work, I now reduce it by 70% 1 hr before exercise and make sure there is no IOB... I consume 15g of carbs, sorry I mean I eat 15 jelly beans before I start, then I consume 10 jelly beans for every hour of exercise.. Quick acting carbs like this are burned through quickly and cause me to spike later.
I don't disconnect from my pump for exercise, don't see the point if basals are reduced correctly.
This keeps me pretty flat, although I usually come home from runs about 3.5 Mouthful of orange juice and I am back up to 4.5. Job dine,