| I found that I can do about 25 minutes of cardio and my bg will fall about 20 mg/dL. So what I do is do 25 minutes of cardio and then take a glucose tab.
This is indoors in a controlled environment. I've found that with rollerblading outdoors, I need to take a glucose tab every 2 miles, even though it only takes 12 minutes.
I believe the diabetic athletes just get really good about
1) watching the time between their last meal (with insulin) and their workout
2) having glucose tabs or sports gel to bring their sugar up during the activity. | 
