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Branson Half Ironman Basal Plan

October 4, 2010

I thought I’d share the process I went through to figure out my basal/bolus plan for my first Half Ironman a few weeks ago.  The night before the race, while my wife and kids were down at the pool, I sat down at the desk in our room at the race hotel armed with my iPhone, a note pad, a pen, and everything I planned to eat, and I laid out my plan.

WARNING:  Insanely nerdy diabetic triathlon stuff to follow! Also, this is *MY* plan and is based on things I’ve learned during training.  It’s not perfect, but it’s close.

I planned on eating 300 calories per hour over the course of 6:30 hours (I wound up finishing in 6:55:58).

Planning out the bike leg, 56 miles/3:30 hours was my main focus.  3.5 hrs * 300 = 1050 calories needed.

4 Bottles of Gatorade:  600 calories, 154 g carbs
1 Powerbar: 240 calories, 44 g carbs
2 GU (energy gels) 200 calories, 50 carbs

1040 cals, 248 carbs.

248/15 = 16.5   (I took the number of carbs and divided by 15 to get that total number of insulin units needed on a normal day).

16.5/3.5 = 5  (Number of units divided by the hours expected on the bike).

5 /  2 = 2.5  (Cut the units in half to account for exercise).

So, 2.5 units/hr is what I would start with for my basals.  I learned from previous rides that I didn’t need to included my normal basal amount in this number.

For the swim, I planned to eat 1 GU right before the start and for the run, I would eat GUs as needed based on my BG numbers and also drink Gatorade on the run course.

Finally, in a row from top to bottom I wrote out the time starting with my race start time.  7:20, 8:00, 8:30, 9:00…. etc….  1:30, 2:00.  Then next to the time, I wrote out what I would set my basal too.  I used a basal pattern on my Minimed pump to do this.  During training, I knew that I normally spike after the swim, so the first thing I planned out was a 2 unit bolus after the swim, just before getting on the bike (NOTE:  I swam without my pump, 40 minutes, and didn’t lower my basals at all the morning of the race to account for not wearing the pump and nerves.  Normally I lower my basals by 50% for 1 to 2 hours before exercising.  Also, note that I woke up at 4:00 AM and had a small snack with around 30 g of carbs).

8:00 – Bolus 2 u, Basal to 2.5
9:30 – Basal to 1.5
10:30 – Basal to 1
11:00 – Basal to .5 (left basal at .5 for remainder of the run)


This is still a work in progress.  I can use a higher basal on the bike, but need a MUCH lower basal while running to prevent lows.  During the race, I was high – 250 – about an hour into the ride.  I tried to prevent this with the 2 u bolus after the swim, but it didn’t cover it.  When I tested at 250, I think I bolused an extra 2 u.  I did come down and was good the rest of the bike, but tested at 77 about 2 miles into the run.  After that I was fine and finished around 120.

My challenges are how to prevent the initial spike after the swim, taking enough insulin to cover all of the carbs on the bike, but still prevent lows early on the run.

I hope this was helpful and not too confusing.  Please feel free to add your tips and tricks.  Like I said, this isn’t perfect yet, but it’s awfully close.

One Comment leave one →
  1. Anne Findlay permalink
    October 4, 2010 12:48 pm

    I’m not sure how to handle the T1 spike without a waterproof pump. My strategy is to jack up the basal about 30 min before the end of the swim, and keep it high about 60-90 min into the run (depending on 70.3 vs 140.6 tri distance). Also about an hour before the run, I bring my basal down, and try to get some extra nutrition in as well. The run is tricky because my pace can be variable depending on how I’m feeling. If I’m running slower than expected, for example, I have to be careful not to spike my BG really high.

    I also eat my breakfast about 3 hrs before the race and then take my full bolus. I keep my basal rate high–like +20% or so–until maybe 30 min before–and preprogram this to start maybe a bit before I wake up.

    Congrats! It’s pretty tricky figuring all this out.

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