Since timing is everything for good blood glucose management, planning your workouts ahead of time is essential. Every night, before I go to bed, I check my training plan and calendar to see when I can fit my workout in the next day and what type of workout I have planned. Most of the time mornings are ideal for me but on occasion, I’ll need to throw in an afternoon or evening workout due to scheduling conflicts. Either way, pre planning helps me control what my blood sugar does.
In a perfect world, I like to have as few variables affecting my blood sugar as possible so that it is easier to control. In general, I try to consider the controlables, that will affect my BG the most.
- Basal: I consider if my basal needs to be reduced and if so how far in advance. It takes 20-30 minutes for my insulin to have an effect so usually, if I’m going to reduce it, I typically do that 30 minutes before my workout.
- Active Bolus Insulin: It is also important to consider if you will have any active insulin in your system during your workout. My bolus insulin is typically working to lower my BGs from 30 minutes after I dose until 4 hours after I dose. Therefore, I try not to inject bolus insulin for at least 4 hours prior to my workout. I find that most exercise will increase the power of the insulin and I’m more likely to experience hypoglycemia if I have active insulin in my system.
- Current Blood Glucose: If I’m running low or at the low end of normal for example, then I may have to reduce basal sooner or eat prior to working out. If I’m running high, I may not reduce basal and might choose a workout that will lower my BGs (regardless of what’s on my training plan).
- Type of Workout: Different types of workouts will affect BGs differently. Generally, low intensity cardio will lower BGs and high intensity exercise (such as HIIT or resistance training) could have minimal impact or even raise BGs.
- Length of Workout: In my experience, a shorter workout generally will have less of an impact on BGs than a longer one. For example, I typically won’t make any adjustments to my basal or consume additional food for a 10 minute run but for a 4 hour run, I’ll definitely need to do both. Similarly a 60 minute HIIT workout may raise my BGs but a 90 minute workout of the same style, I find my BGs tend to drop towards the end of the workout.
- Food: The type of food you eat will affect BGs differently. If I had a high fat meal earlier in the day, I know some of the carbs/protein I ate with that fat could be raising my BGs hours later, even up to 12 hours after I ate. Similarly, I know that low fat protein could be raising my BGs even 3-6 hours later. If I had some high glycemic index carbs without a lot of fat or protein, I can count on a quick spike followed by a quick drop. I also find that alcohol can also lower blood sugar, unpredictably for up to 24 hours* and may tie up the liver function so the dawn phenomenon doesn’t happen at all. Learning how food affects you and considering what may still be affecting BGs during the time you’re planning on working out will make a huge difference in your ability to maintain control.
- Other Factors: There are some other predictable factors, such as the dawn phenomenon, stress and hormones that will affect (often raise) BGs. Although harder to control directly, you can absolutely choose a workout that can complement this. Sometimes, if I’m running high due to stress for example, I may take a walk to lower BGs instead of giving myself a correction. If the walk doesn’t lower BGs enough, I can always correct (usually using a smaller amount of insulin that I would have otherwise) after the walk.
While these are the major things I consider when planning a workout, it is also important to be flexible and prepared to adjust if something unexpected happens. I always carry emergency food (high glycemic index carbs without a lot or any protein, fat or fiber) to prevent hypoglycemia and I’m usually connected to my pump so I can inject some insulin, if needed. In either of these cases, small inputs equal small mistakes so I avoid large amounts of carbs or insulin when correcting in either direction.
*This is a large reason why I don’t drink often and when I do, I don’t drink a lot.
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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.