Its the "dawn phenomenon" when you wake up your blood sugar will generally go higher until you take some insulin and eat a meal. Im no doctor but from my understanding your body starts putting glucose into your body when you wake up to "get you going". I always try to eat food within the first half hour after waking up or my bg will go up 100-200 points! Also, exercise and bg is tricky. If i do light exercise like biking downtown or skateboarding my bg will go down, but if I run hard for 5 miles it will skyrocket. You just have to test a lot and find the patterns....
Another theory that was offered to me was that when your bg is high, your body doesn't know that your cells aren't getting the glucose and can release stored glucose. Exercise can cause additional release of stored glucose and result in skyhigh bg. If I am over 150 bg, I will correct, and postpone the exercise to be sure that I don't cause my bg to go way high. I read somewhere (don't recall where) that a bg of 250 is the cutoff point for most people - that is postpone until you're closer to range (range being the bg level that works fo r you to support the physical activity)
I know when this has happened to be it is because my insulin has gone bad. When I switch up vials the correction happens almost instantaneously.
I've had T1 for 4 years now, and sometimes your blood sugar will go up after exercise. I think it depends on the amount of sleep, and if you ate that day. Before going on a walk, I usually don't eat anything, just drink a glass of milk helps me. Careful about taking insulin later though, because even though its high now, you'll drop later!