Endurance training is my personal favorite kind of exercise and if you follow my blog, you’ll see that the majority of my workouts are some type of long form cardio. There is just nothing quite like finding a rhythm and getting lost in your thoughts, lost in the woods or letting your mind go completely blank. It’s meditative and relaxing and has become a bit of an addiction for me*. I tell everyone that I run for my mind more than my body and that I would indeed be a crazy person if it weren’t for running.
When I was first diagnosed, one of the first things that crossed my mind was ‘How do I get back to running?’. So I did a lot of experimenting early on to figure out what I needed to do to regain and keep up my running habit. This is what typically works for me for long steady cardio, keeping in mind that…
Typically, endurance training will lower my blood sugar and often lower it significantly.
Usually**, I reduce my basal insulin 30-90 minutes before I start an endurance workout and end it 10-30 minutes before I stop working out. For a 60 minute run, for example, I might reduce basal 30 minutes in advance and end it halfway through the run. The idea here is that my insulin usually takes 30 minutes to start taking effect so I want it to stop lowering blood sugar on my run and start kicking in again once I stop. The exact timing will vary from person to person (and possibly day to day) and will depend on what kind of insulin you’re on.
I also make sure to “carb up” during my workout. The worst thing that can happen is that your blood sugar will drop low so I always carry carbs for endurance workouts. I will typically not focus as much on the number on my GCM as much as I pay attention to the trend. If I’m trending up, maybe I need more insulin. If I’m trending down, I probably need some carbs. I’ll usually have a few carbs at a time and check every 10-20 minutes or so to see how they are effecting my sugars. If you consider that high glycemic index carbs that are typically used for endurance training will take roughly 15 minutes to actually hit your system, you can avoid overdoing it by spacing out the timing a bit. Again this will vary from person to person so adjust this timing to how you know that carbs affect you.
I avoid insulin onboard at all costs. If this means I can’t eat and/or inject for four hours (the amount of time my insulin lasts in my system) before an evening workout, I try my best to make that happen. Having active insulin in your system and adding cardio will drop most people’s blood sugar extremely fast and will require a lot more carbs to keep BGs within a safe range. This causes a lot of frustration for newer T1 athletes because they wonder, ‘What is the point of working out when I’m eating all of the calories I’m burning?’. While this is oversimplified and working out has many other health benefits, it is helpful to understand that if you have less insulin in your system, you won’t need as much food to keep BGs in a healthy range.
On that note, be aware of protein and fat. Learn how they affect your BGs and use them strategically. You can use the delayed effect of these macro-nutrients to keep BGs steady during endurance training or they can spike your BGs way high before or after a workout if you don’t time it right. This will take some self-experimentation to figure out exactly how it will affect you and how much/what kind of protein you need to keep BGs stable.
Keep in mind other things that can affect your BGs such as hormones for women, alcohol up to 24 hours before, the dawn phenomenon and race day adrenaline. If your BGs aren’t doing what you would expect, be ready to adapt and err on the side of going high. It’s safer to be high than low and you can always bring it back down with a little insulin later on, if needed. I have been known to over correct an oncoming low with food mid-run and then inject insulin for it towards the end of my run or right when I finish to avoid going high.
These are my general rules of thumb but again, the most important thing is to be flexible and adjust as needed. You can cut a workout short if you’re going low or extend it if you’re trending high (and have the time to do so). You can eat more or less and adjust insulin levels to stay in range. Play with the variables and find out what works best for you!
Endurance training isn’t for everyone and there are plenty of ways to stay active if you hate it. Really the best workout is the one you will do consistently! More to come in a future post on BG management strategies for other types of workouts!
**If I’m running in the morning and anticipate the dawn phenomenon spiking my BGs high, I usually don’t reduce basal at all. You may or may not be able to get away with this depending on how the dawn phenomenon affects you.
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The content on this site is not intended to be medical advice. Always consult your doctor before beginning a fitness regimen or adjusting your diabetes management strategy.