CGM use while exercising

Continuing the discussion from Do you love to bicycle? Come say hi!:

This topic is inspired by some of my recent experiences and comments from @DrBB and @Thas.

How do you use your CGM during exercise to help prevent lows (or highs for that matter)? Also, how have you overcome challenges in using your CGM during exercise?

For me, I ride a recumbent tricycle and find I am able to wear shorts with a belt so I can “easily” see the CGM when I stop at a traffic light. However, I am plagued by at least two things.

The first is when the CGM drops below my low threshold and the numbers turn red. I can’t read them in bright sunlight. I sort of solved this by turning off the low alarm which keeps the numbers white until I fall below 55 then they are red again.

The second is once low, the CGM (really it’s the interstitial fluid) takes a longer time to catch up to what’s really happening with my BG, so I might think I am low and over-treat. Of course, the reality is my rides are so strenuous that I am constantly working to keep my BG up, so even when the CGM is reading too low, I will need to eat some more glucose tabs and/or a protein bar at some point.

I don’t use the CGM to prevent highs and lows as much as keep an eye on my BG so I can anticipate the various courses of action. I also found it very effective as kind of a “spotter round” to see how my plan (temp basal, snacks, etc…) are working and make adjustments. When I started running, I would crank my basal way down and have snacks but I realized that 10% didn’t seem like quite enough, particularly for longer runs where even the “straight” people will be having various snacks, gels, etc.

I don’t find that it lags much more than 20 minutes behind my BG so it’s usually more of a “tiller”. I usually have like a yogurt (no bolus) before a 30-50 mile bike ride and maybe some crackers or a Kind bar or 1/2 PB sandwich at the turn on those rides. I did the Tour de Cure last year and ate at a lot of the rest stops and seemed to hover 70-100 but there’s always another stop coming up.