Hi Karen,
If your best result in ages is 7.4 and you're sugars are going as high as 21 following exercise and no food, I would suspect your analogue insulin to be at fault. The levels you are reporting are not good.
I'm on animal insulin, after years on "human" insulin and horrendous 4 years on lantus(analogue similar to Levemir), with ups and down that didn't make any sense or have any consistency. I have recently gone for long jogs in the morning with no food prior to exercise and my results are as they should be; meaning my blood sugar lowers and stays at lower levels throughout the day. Exercise can cause raises in BG levels initially, but 21 is a bit high.
Analogue insulins do NOT do as they are supposed to for many people, and as the majority of patients are on them or being changed to them, there will be plenty of studies done, under the assumption that these medications are working as they should, which will come up with every theory under the sun why patients are having unusual responses. In the same way when patients report feeling extreme lethargy and muscle pains on these insulins, they will be diagnosed with illnesses suchas Fibromyalgia, CFS, etc;.or have it blamed on being diabetic, rather than these problems being recognised as side-effects of analogue insulins. That's my and many others experience anyway.
If your insulin was working as it should, like real insulin, your sugars should not be going as high as 21 after doing a workout DVD.
What does your doc think of your general control, have you been offered any support in getting your levels down?
Trouble is with most docs being ignorant of real "animal" insulins, and how insulin should be working, the tendency is to blame the patient when things go wrong
Hope that's not too much of a rant, but if 7.4 is your best result in a long time you need to see your doc.
Jus