Total Daily Insulin Versus Cycling Time

Thanks to my super-fantastic coach and team director Kori, I have been logging my workouts since she started working with me late last year.  From my insulin pump, I can also pull off my total daily insulin amounts (or "TDD" for total daily dose) since the beginning of time, give or take.  I thought it might be fun to just plot out my TDD as a function of my cycling time, even though the results are probably as shocking as showing that washing hands reduces the spread of colds.  Anyway, I decided to just do a very simple linear regression of the data between January and March, 2011.  This model ignores variables such as what other exercise I did that day (I often walk about 40 minutes per day), whether I ate more or less than normal, my weight, how old my infusion set was, etc.  In short, the only variable I am considering is time on the bike.  But there still is a clear trend that shows with increasing time on the bike, I took less insulin.

An Overly Simplistic Model But Still Sort of Interesting

For those who like details, the slope was -0.046 U/min, the y-intercept was 35.3 U and correlation coefficient was -0.65.  If I included only March, rather than January through March, the correlation coefficient was -0.68.  The mean TDD for January was 32 U and was 30 U for March.  Total cycling time was only 90 minutes more in March although the intensity was higher.  My weight was about 5 pounds less in March.  Again, one of the most important and obvious variables affecting TDD is calorie intake, which is not included here.  But still it was fun to plot this out since the data was readily available.   Maybe I will be better about logging total activity time, including other forms of exercise, for a period of time.  If I am super motivated, I might even track calories although I can only stand doing that once in a while.

...And 18 More

As the finale workout for our last peak week of training for Ironman Coeur d'Alene, I ran 18 miles early Sunday morning, about 14 hours after winding up our 124-mile ride. One of my favorite running spots in the Bay Area is Sawyer Camp Trail, which runs alongside Crystal Springs Reservoir. It is not uncommon to see deer along the trail, blue jays flying from tree to tree, and rabbits hopping out of the way. I felt surprisingly good and refreshed for the run--it must have been that sushi and miso soup the night before! I was pretty happy with the BG's as well. I fiddled around a lot with my basal rates, and would watch the resulting pattern with the Dexcom. Clearly there is a delay between a basal rate change and a change in blood glucose, but I was running for a long time! On the Dexcom, my BG's varied from about 125 to 148 while I was eating pretty steadily, 250-300 calories per hour. One of my revelations this weekend is that, even if I come in with a basal rate that is too high, it won't affect me for more than an hour or so. This is not the same for boluses, however, which seem to last with me for many hours.

I Sort of Missed You, Pump

After about a month of using Levemir 2-3 times per day, I am back on the pump. Trying to figure out how to take enough to prevent highs without crashing was tough. I found that about 3-5 hours after a dose that was too high, I would drop at a remarkably constant and steady rate. It was sort of cool to see such a straight, downward-sloping line on the Dexcom, but not if it was 1 AM and I was waking up with another BG of 39 and knew that after I blew the diet by eating 200 calories in GU, I would wake up in another 4 hours with low BG again. Still, I was impressed at how much steadier Levemir is than NPH, which was the long-acting insulin I used when first diagnosed.

The Levemir regimen we finished with was 6 units between 5 and 6:30 AM, 3 units between 1-2:30 PM and 2 units before bed. This worked fairly well although by the morning, my BG would start to rise. Increasing the evening dose to 3 units led to unpleasant lows. I had similar issues with the morning dose.

Although I am not continuing with Levemir for now, I definitely think it was helpful to take a break from the pump and to figure things out with a long-acting insulin. I have a much better understanding of my insulin needs throughout the day and during exercise and hope to be able to transfer this knowledge over to a more effective use of the pump. One of the biggest discoveries was that, if I want to eat anything during exercise, I need a lot more insulin than I had been taking, and definitely more than I would need at rest.

The mental freedom of being on a long-acting insulin was nice, though. There is some comfort in being "good to go" for many hours and not needing to be connected to anything (although I was using the pump for boluses and also the Dexcom).