Exercise Rebound

I’ve noted this in another post but would love to explore this topic further here for broader discussion of this topic.

Lately when exercising soon after a meal while bg is the steep climb, I’ll experience either a plateau in the climb or a dramatic fall in the climb (as much as 70 points) only to have a fairly dramatic rebound of about 40 points within an hour. To be fair, this might not be a true rebound. More likely to be a continued postprandial spike that was halted by the workout. By workout, I usually mean a quick jog on the treadmill or a 25-30 minute brisk walk.

To address this anticipated rise, I’ve tried running an increased basal rate on my pump. Additionally, I’ve given extra boluses after finishing exercise to try to ward off the anticipated climb.

Other thoughts on how I might address this?

Tell me about the exercise. What intensity is it, and how long does it last? Those factors play a big role in all of this.

But a couple of things I thought of:

I really would encourage you to not do that. A couple of things.

  1. Post-meal you have IOB. That makes your exercise BG more sketchy. The ideal time to exercise is a few hours after a meal, when IOB is gone. I know this is not always possible, but that is a much safer way to do it. And much less susceptible to issues such as miscalculating your dosage and meal numbers, or variations with different foods metabolizing at different rates.

  2. Exercise can actually slow down how quickly the foods you eat are metabolized. This depends a lot on the nature of the exercise and the intensity of the exercise, but it is a fairly common phenomenon that exercise slows down the digestion system in order to conserve energy for the muscles. And at the same time, your rate of insulin absorption will speed up as the blood moves faster, your temperature increases, and the muscles near the injection site are used. All the numbers you are used to - rate of food abortion and speed of insulin absorption - are totally turned upside down!

  3. The best time to eat is immediately after exercise because you get the benefit of better muscle glycogen restoration and the repair of muscles. (Please see:

  4. Your post exercise rise can be a combination of the food possibly coming in later (slowed down by the exercise) or the hormones that are released from the exercise (if it is of significant intensity). Intense exercise can cause the release of hormones (epinephrine (adrenaline), norepinephrine, and cortisol) that increase the release of glucose by the liver.

I know it is challenging to work the exercise in at particular times. Are you exercising after a meal because of schedule restrictions, or are you doing that because you were worried about it not being safe to exercise on an empty stomach?

Thanks for this detailed reply, @Eric!

So, most of the time I am on the treadmill to try to intercept a rapidly climbing high. Usually post dinner. Why this time? Because this is the only time of the day I have childcare help. So, someone else can baby-chase while I chase my blood sugar. I understand it doesn’t work for everyone and could be dangerous with IOB, but for me it usually helps the insulin work faster. And I don’t think I’ve ever recorded a post-exercise low. But I hear you that it could slow down how quickly the foods are metabolized.

I will try experimenting with pre-meal exercise–maybe on a weekend.

Thanks for your detailed help! I do think that the rise is a combination of both factors at work (proximity of exercise to eating and a release of hormones). Both seem to be at play in these post meal scenarios.

This is effective on multiple fronts - speeding up insulin absorption, increasing the rate of muscle’s uptake of glucose, and slowing food absorption. But the post-meal rise is quite possibly the remainder of the food being absorbed later.

The post exercise spike from hormones depends greatly on intensity.

It is important to mention that intensity is not a speed or duration that is the same for everyone. Intensity is just your body’s perception of the exercise. Intensity is different for everyone.

For your exercise, is it something you do everyday that is about the same (probably a lower intensity)?
Or is it sometimes harder on some days and sometimes easier (variable intensity - sometimes high, sometimes low)?

It’s good to try a few different things and see how they affect you. So if you can, definitely try it without eating sometime (and for longer runs cut your basal !).

But regardless, make sure you restore some carbs after exercise. That will help your run on the next day.

And if you have to take insulin after a run so you can restore carbs and not go high, do it. I take insulin after every run. That’s just another instance where real-world does not match the diabetes playbook they give you in the Endo office. :slight_smile:

Side note - imagine how much fun you can have with it at your next Endo appointment. They ask you, “Why did you take 3 units of insulin at this time a few hours after your dinner?” And you answer, “Because I had just finished a hard run…”

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I’m off the running bandwagon these days (knees, etc.) but when I was 30-40 miles/ week, it was a great feeling to go to the doc, the first thing the nirse does is check your pulse and, if it’s 55 bpm, they go “oh, do you run?”

As far as spikes, it’s aerobic spikes vs. aerobic burn pushing bg down. Another unintended side affect of my short-lived distance running career was Turkey Trots and trying to run a “fast” 5K, which would always blow up my bg on race day.

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