I've been T1 diagnosed some 33 years ago and over the last 10 years have put a considerable amount of weight on, this is due to my job being sat on my backside for considerable amounts of time. I self prescribed the Libre some 24 months ago and after a while grew the confidence to reduce my carb input which allowed me to loose a stone. Although I struggled to loose any more, So I decided to get back on the bike. What I've found there is no rhyme or reason with Diabetes.
A few weekends ago I Carbed up (3 slices of toast) pre ride with no bolus insulin, Started the ride at 12 mol/l, mid ride at 10 mile my numbers were <<6 mol/l so mars bar and finished ride after another 12 miles with numbers <4mmol/l so had a second mars bar (Other chocolate bars are available) and a hour or two later my numbers were 6mmol/l. Two weeks later I did the same but numbers were 10mmol, 11mmol and 12mmol, the same toast, the same basal & bolus, the same previous even meal, and no mars bars this time. No rhyme or reason with diabetes!! The libre gave me the info to make those informed decisions though!
On the whole I usually find my numbers usually fall for some 4-6 hours after a vigorous exercise, I recently did a evening ride which had my numbers falling well into the early hours which I will remember next time!
Only suggestion for those looking at exercise, Find something you enjoy. Don't care what people may think, Its their issue not yours. I often say to people I'm a vision in Orange as I have a vivid orange cycling top. Push yourself a little each day or each time you exercise, and the pounds will start coming off when they are ready, even if you are eating more carbs to keep your blood sugar levels.
The Libre is working for my as my last visit to specialist my Hba1c was 5.5 which both me and my specialist were happy with!