You'll see a book over on the righthand side that I have sworn by for the effective treatment of both Type I and Type II Diabetes for years.
One of the principles of effective exercise Dr. Bernstein propounds is that you work at maximal efficiency and exhaust the muscle. This is important for maximal fitness but also for draining the muscle of glycogen stores which is essential for managing diabetes.
This article also argues the same thing about exercise efficiency. Don't spend more time exercising than you absolutely have to!