Thursday, November 6, 2014

Exercise in a LOW context


This is an exercise report. Not a recommendation!
Do not try to replicate anything described on this page!

Basic Data: boy 13y10m approx 164 cm 51 kgs - MDI - typically 5 N 6 N 5 N 16 L

General context: we have been fighting the dawn phenomenon lately. We can control it with higher Lantus doses, but then are hit by early nights lows and a general downtrend during the day. We have also noticed that days with a decent amount of physical exercise led to good nights without increasing the Lantus dose.

The day's context: (CGM trace below)

  • 4:30 AM climb to 130 mg/dl (CGM) in the night. 150 mg/dl at the BG tester. Corrective action based on previous nights patterns: 3U Novo. Recalibrate. 
  • 7:00 AM Wake up at 125 mg/dl (CGM) 101 mg/dl (BG). Usual morning calibration. In both cases, the Dex was probably running a bit late but was in line with the trend. 3U Novo at 7:15, reduced from the usual 5 because of the stacking with the 4:30AM dose. 
  • 9:90 AM Small spike meal followed by a low. Hindsight: could probably have reduced the 7:15 Novo to 2. 
  • 11:00 AM Correction spike, better safe than sorry. No overshoot: good.
  • 12:00 PM Standard Meal - Novo 5U 
  • 15:00 PM Again small low 3 hours later - there is a steep slope on the way home.
  • 15:45 PM Correction approximately 15 gr of carbs, low but very little insulin on board at that time.
  • 15:50 PM CGM at 69 mg/dl in a steep climb, BG confirms steep  rise at 95 mg/dl
  • 16:15 PM Exercise started.

Exercise: threadmill - 4 km total distance - interval training by 250m segments alternatively at 8 km/h and 16 km/h. Last segment of 500M at 16 km/h. Couple of minutes of pause after 15 mins to drink and check general feeling. Exercise duration excluding pause and warm up: about 20 minutes, cooldown 20 mins slow walk. Polar HRM recording below.

Post Exercise: trending low for about 5 hours, although not as badly as the CGM indicates (77 mg/dl BG vs 60 mg/dl CGM at 18:34 for example). Steady at 83 mg/dl CGM since 10 PM - no calibration entered in low as calibrating the Dexcom below 80 mg/dl has proven to be a lottery.

Summary: obviously not something to try at home if one is uncomfortable with lows and unable to monitor constantly for the rest of the day and possibly night. The carb loading for the exercise seemed to have been insufficient and a glucose debt + increased insulin sensitivity follows. Note: we have previously seen highs of 180 mg/dl with low carb doses (5 grs) when IOB was insufficient. Critical hour to watch 3:00 AM during the following night as purely aerobic exercises delayed lows usually appear after 11 hours (in our case, may vary greatly from individual to individual).

Post Mortem: (added 11/7/2014)  well, the plan failed on two accounts. Despite the exercise, we had our typical increase. But to make it worse, this is a night the Dexcom did not want to cooperate, possibly because of a mild compression. Or just because it did not want to. BG started to raise at the usual time, but not as steeply. In fact, they were rising as a 3:30 AM BG blood test showed. 3U novo were injected, and life resumed.

Feedback: thanks to the two readers that contacted me directly with the suggestion that a pump would probably solve the issue. I do agree that this would probably be the best course of action but there are two factors that we have to take into account.
  • while Max is doing a great job at controlling is blood sugars, he isn't very careful with some of the hardware around him and is definitely not the most scrupulous adolescent.
  • that pattern isn't always present and its intensity varies a lot (corrections range is 1U to 5U). I wouldn't sleep more without a pump with a suspend function and a reliable CGM.
Thanks a lot for your feedback MGO and LT!

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