Keeping Stable Blood Sugars While Training For A Triathlon

For far too many years after I was diagnosed with type 1 diabetes, exercise felt like a “necessary evil”, where I KNEW that it was healthy and good for me… but glucose levels were a nightmare to manage.  

Half the time I’d plummet into a low and consume more calories than I’d even burn during the workout… 

The other half of the time I’d have to pause at the end to give insulin because of a high glucose event, I just couldn’t figure it out!  

Over a decade of research, trial and error, and experimentation with my diabetes, and now I’ve figured out what works best for me, and one of the lessons that’s been critical to understand is one that I want to share with you today.  

For simplicity’s sake, we’re going to ‘lump’ exercise into one of two categories: anaerobic (think weight lifting) and aerobic (like walking, jogging, or running).  

Without diving too much into the science between how we can build predictable blood sugar formulas and how to determine exactly how to keep blood sugars stable, I want to introduce what I call “slow burn or fast burn”.  

See, when I would weight lift back in college (when I was a little more obsessed with body composition admittedly), I’d notice that my glucose levels would either be stable or even go up a little… 

But for the next few days it seemed that I wouldn’t spike as much after big meals.  

This can be attributed to more of a “slow burn” effect where my glucose levels benefit from a boosted insulin sensitivity for days on end as a result of a good gym workout. 

Cardio on the other hand, more of a recent exploration with my half Ironman training (swimming, cycling, running), has led to immediate and sizable drops in blood sugar during the activity… 

With only a little boost in insulin sensitivity for about the next 24 hours.  

This is what I refer to as the “fast burn” where most of the impact is localized to the exercise itself. 

Of course, your experiences may differ, but I’ve actually noticed a similar trend with most of my T1D clients as well… 

What I work with my clients on is their “Activity Impact Ratios” where we build out those blood sugar formulas I mentioned earlier. 

To simplify a step further though, and hopefully make this easier to remember, I want to use an example of a campfire.  

Let’s say you want to get warm NOW, but your only source of fire is a lighter… so you decide to build a fire.  

If you grab a thick log, it’s going to take forever to start to catch and produce heat…  

So instead, you realize that you’d be better off grabbing some small twigs and sticks with some newspaper because it will light on fire much faster and easier, producing immediate heat. 

THIS is the fast burn of cardio with an almost immediate impact on blood sugars (for most people).  

If, however, I recognize that I want heat to last more than a short while, maybe for cooking, I want to take the time necessary to set that thick log on fire because it will produce a more consistent burn that lasts longer.  

THIS is the lasting “slow burn” of weight lifting as it lays the foundation for lasting insulin sensitivity for multiple days on end.  

As I entered into my triathlon training a year ago, I shifted from all weight lifting to a mix of weights and running, then to almost exclusively cardio based exercise.  

What did this do to my glucose levels?

Initially, LOTS of drops in my levels that almost led to lows (thank you to Dexcom CGM for helping me to see my glucose levels in real time so that I could use the trend lines to take early action and avoid the lows).  

Over time though, I remembered the lessons above and adjusted my diabetes management strategy to match my exercise routines.  

Knowledge is power, implementation is KEY.  

I hope that helps, and feel free to reach out if you have any specific questions to team@ftfwarrior.com .  

Turns out exercise IS good for you AND possible to maintain steady levels (as long as you have the right tools and strategies available).  

Keep up the Fight.  
Matt Vande Vegte, CPT