I agree with the other comments already made
Let me try and answer your questions about exercise and diabetes. I am not aware of any connection between the onset of diabetes and over-exertion. Exercise helps people with diabetes keep their blood sugar in good control and within a normal range. Glucose is used while exercising, which would lower the blood sugar level, not raise it. If you are predisposed to developing type 1 diabetes, no amount of exercise will change this. On the other hand, type 2 diabetes is linked with obesity, and exercise would definitely help with the prevention of that type. The hemoglobin A1C measures the average blood sugar level over a 3 month time period. This test is used by diabetics as a tool in keeping their blood glucose readings in control.
You ask an interesting question. I'm not an MD, and you might want to talk with an exercise physiologist about the particulars of your own exercise routine, but ... exercise is not a cause of diabetes. For folks with diabetes, exercise is an important part of our strategy for staying healthy.
Hemaglobin a1c shows an overall average blood sugar for the past 90 days or so. There is not a direct formula, in part because different labs using different measurement scales, so a given number from Lab A would translate into a different average BG (blood glucose) than that same number from Lab B.
If you have had a1c tests done, you can get the "Lab Normal" range info directly from your doc or lab.