Hmm, when I was first diagnosed prediabetic my blood sugar used to increase after running. In the end i stopped taking it around exercise as I liked running and didn't want to stop. I went straight onto a strict low carb diet. My gp said it was definitely genetic as I was not overweight at all.
Having had a normal hba1c for 11 years, but still with an abnormal response to carbs, I will be interested to see my blood sugar with exercise when I use my free libre two week trial.