The Unpredictability of Blood Glucose in Sport

Sport and blood glucose, how does it affect you?

I used to beat myself up pretty bad when my blood sugars would fail me on a run or a bike ride or in a race, or any other activity, really. Even just a walk. And truthfully, I’m not going to lie, sometimes I still do.

I get so frustrated when Dear Diabetes interferes with anything in my life, but especially with my sporting activities.

I’ve always been of the mindset that diabetes does not define me and it sure as heck won’t stop me. So when it does, oh man, I get so freaking angry and frustrated, and the person I take it out on is ME!

Does this sound familiar to you? Do you experience it too?

Forced to halt mid 19 km run due to low BG

It’s hard to remember the unpredictability and stranglehold that Dear Diabetes has on us. There are so many factors that contribute to blood glucose management, often things that are completely out of our control.

Let’s talk about sport specifically:

  • Do you go out first thing in the morning or later in the day?
  • Do you eat before you head out or do you eat after?
  • When was the last time you bolused?
  • Do you still have insulin on board?
  • What type of exercise are you doing? Is it a light walk or is it Crossfit?

All of these things are fairly common to our diabetes strategies and are generally things that we can control for.

For example, if we’re going out for a run first thing in the morning and we tend to eat before exercise, we can get up a few hours earlier to limit the amount of insulin in our system when we do go out, or we can reduce the amount of bolus to again limit the amount of insulin in our system, and we can also adjust our basal rates.

What we can’t necessarily control for is:

  • Temperature
  • Race-day anxieties
  • General life stresses
  • Poor sleep (see race day anxieties above)
  • Mixed intensity training
  • Level of fitness

All of these can impact blood glucose, whether it be increasing BG, decreasing BG, or maintaining BG.

Some, like high to moderate intensity exercise, may either increase or decrease BG depending on how your body reacts that day. And we don’t always know how our bodies are going to react. For women, if they’re going through menstruation, those added hormones can wreak unpredictable havoc on BG management.

Blog-Sport & BG

So, what do we do?

We try our best. And we keep trying.

We write things down.

For those of us in training, many of us live pretty predictable lives – we tend to eat the same foods, at least during training, races, matches, and competition, we try to get adequate sleep, and we generally know the intensity of training ahead of time.

Track your exercise intensity during these times and how your BG responded. Track your fuel and how your BG responded. Track your sleep and how your BG responded. Track your menstrual period and how your BG responded.

Make adjustments as needed and, yes folks, track how your BG responded to those adjustments 😀

It’s not perfect. We’ve been living trial and error since diagnosis and right now that’s what we’ve got to continue doing.

But what we are NOT to do is beat ourselves up.

Diabetes can be a real jerk face sometimes and it’s nothing that we did!

Do not let it stop you from being the active awesomeness that you truly are!

* Riddel, M., Gallen, I., Smart, C., Taplin, C., Adolfsson, P., … Laffel, L. (2017). Exercise management in type-1 diabetes: a consensus statement. Lancet Diabetes Endocrinology. 5, 377-90.









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