Prepping for intense exercise

@Eric referred to you on the tudiabetes forum… here you have some wisdom on how to prep for intense cardio or lifting… what strategies for lowering basals or carb intake… slow, fast, medium etc. Your thoughts would be appreciated.



Welcome, @hoya, to FUD! Eric is our go-to guy for exercise information. Here’s one recent post that might interest you:

Welcome @hoya!! You’ve come to the right place… Eric is the resident exercise guru.

Introduce yourself here Welcome, introduce yourself here!


Thanks… HIIT is what?

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Welcome, @hoya!

HIIT = High Intensity Interval Training. It is a kind of exercise with short stretches of high cardio activity followed by intervals of recovery.

High intensity interval training–seemed like something similar to your interest. If you select the Sports and Exercise category you will find Eric’s write-ups on various aspects of exercise plus lists of posts on exercise questions.

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Hi Hoya - it’s what I’ve been doing to get fit and build some muscle
I’ve found that 40mins is the max I can do but if I hit it really hard with no resting and lifting reasonably large weights - then I get a good cardio and also strength training and if I stop after 40 mins then it doesn’t normally rise my blood sugar that much - my resting heart rate has dropped from 78 to 60 in 3 months and I’ve put on a good 6lb I guesstimate of muscle so it’s defnitely working
Keeping it short means I don’t have to carb load and it meets my bg remains stable / I am on a low carb diet so don’t want to carb load as well
Per the post above - I find if I cool down the cardio element or go too much on the cardio vs strength - then my bg will spike a lot during (about 15mins in)
I have really bad PIR right now so that also means I have to take massive amounts of insulin to lower my BG - that separate but a pain - I had to take 16 units of humalog this morning to get my Bg to go down from 150 to 80 which is ridiculous - I think that’s what caused the problem in my earlier post so having no big rise and no need for insulin is what I am aiming for as well as getting fitter


Welcome @hoya!

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Hi Hoya!
There are a lot of different things that can happen depending on the type of exercise, the intensity, and the duration.

When you mention “intense cardio”, can you tell me more about that? Is it a very short intense session, or a longer intense session?

The reason I ask it it can depend greatly on what happens. A 5k race would affect you much differently than a 10 mile race. Even though you are going as hard as you can for the race, the difference in heart rate for the 5k would be much higher.

If your fitness level is high, very short intense sessions lasting just a few minutes may not affect your BG. Slightly longer intense sessions, such as a 20-30 minute run at all-out pace would probably cause you to rise. And a longer run, such as 60 minutes at race pace could cause you to drop.

Weight lifting is more likely to raise your BG. So there are a lot of different things that can happen depending on the workout and the order you do the exercises.

Tell me a few things. Are you on a pump? How many carbs do you eat in a day and what is your weight? (or if you don’t want to share your weight, you can just tell me the carbs per pound without telling me the numbers for either one :wink: ). And then describe your workout, the timing of it, duration, the order you do it (don’t need all the exercises, just tell me if it is cardio and then resistance, or resistance and then cardio).

And then we can discuss some things for post-exercise - carb and protein intake, BG management, etc.

The best plan really depends a lot of all the factors.


Hey… see above.

So if I am understanding this correctly, it sounds like the resistance training is not on the same days as the cardio. That makes it easier from a BG management standpoint.

Is the 30 minutes of cardio a high-level? Is your heart rate close to 95% of your theoretical max heart rate? Or does it feel like you could possibly keep the same pace/intensity for 45-60 minutes? That intensity level will probably indicate whether this is a workout that will lead to a spike or a drop.

Just some very general guideline - this varies for everyone depending on fitness level - greater than 95% of your max heart rate can lead to a BG spike. 80%-95% is more likely to be in the range of a fairly quick drop. And less than 80% might be more like a slow drop. All that depends on a person’s basal and IOB and how much they are fueling daily and their fitness level. It varies, so you need to find your %'s.

Your carb intake is on the low side. That will make you more likely to drop from cardio than someone who has a higher carb intake relative to their weight, and more likely to spike a bit higher from the weight training. The reason is that without the carbs to fuel your exercise, the amount of muscle glycogen can become limited after several consecutive days of exercise. Without the muscle glycogen, the cardio will pull as much glucose as it can from your blood and from everything you eat to fuel that activity. And for weight lifting your liver will release glycogen for fuel, so that can lead to a spike.

One possibility is to occasionally carbo load to make sure your muscle glycogen has been restored completely. Or to alternate higher carb days with lower ones. Put your higher carb days on the days before you do the cardio.

I know people don’t want to eat a lot of carbs because they may be trying to lose weight, but weight-loss can be accomplished with exercising at a lower intensity which doesn’t require as much carbs because it can be fueled by fat-metabolism. But for higher intensity exercise, there comes a point after several days when you have completely depleted your fuel-source, and that can lead to huge drops and spikes depending on the type of exercise.

As a general rule - it’s best to exercise 4 hours or more after your last bolus, because limiting IOB is very helpful. If you do it 2 hours after your last bolus it is manageable. Less than 2 hours makes it tough, because you have too much IOB floating around.

For the basal management for the cardio you are doing, it depends on the intensity, so let me know how intense it is relative to the notes above and we can discuss that a bit more.


Thanks @Eric. I’m not sure how to quantify intense – can you give me some parameters?

Maybe start with heart rate and perceived effort. How close to the simplified general theoretical maximum heart rate are you getting? (Percentage of max)
220 - age in years = theoretical max

And on a scale of 1-10, with 10 being hardest, what effort is it for you?