Cardio vs. Strength Training

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Are there very many people out there who find a big difference with their Blood Glucose Levels (BGLs) when they do cardio rather than strength training?

I am Type 1, but the numbers should be about the same regardless of your Type I think ... right?

I find that when I do cardio, my current BGLs drop like a rock. I always have to have a snack before and lower my Insulin levels. Then, for the rest of the day my BGLs are low. I have to lower my Insulin for the entire rest of the day and be careful what I eat. However, it only seems to affect me for that day.

When I do strength training, my current BGLs seem to stay relatively the same as when I start. I don't usually have a snack during the workout, and I eat often enough that my snacks around the workout cover me for calories and glucose. However, that said, I have big issues with my BGLs for two days following. They will be quite low and I will have to lower the insulin for two days based on the workout.

So, has anyone else noticed the difference in their BGLs when they change their exercise routine?

My doc suggests that I keep the same workout so that I know what my BGLs are going to be. I don't follow this advice and I don't do the same routine each time because I am aware that I should be changing my workout each time to vary the muscle clusters being worked out. (Eh, he's an endo, not an athlete, can't ask him to know everything!)

Does anyone else notice this trend? What do you do to prepare for it? Any suggestions or reccommendations?
Posted about 11 years ago
Posts: 0
Very interesting question! Ok, this is my understanding from what I've read and the research that's out there...

Aerobic exercise (cardio and things that keep your heart rate at about 70%-85% max) tends to lower your blood sugars. The reasoning for this gets pretty technical but basically for someone without diabetes, when you begin to exercise your body automatically stops producing as much insulin to compensate for the exercise. In someone with diabetes, if you already have insulin on board your blood sugar will drop because of the physiological reaction that occurs in your body with exercise. For that reason, it's important to consume carbs and maybe even lower your insulin (consult your endo though!) before exercise. For me personally, I am on a pump and knock down my basal rates about 1.5 hrs pre exercise. Depending on the form of exercise and duration I also consume about 20g of carb every 45-60 min. I'm training for our triathlon so my workouts tend to be long! It's interesting because I've also found that swimming lowers my BG a lot quicker than running or biking. I also go low about 2-4 hrs after you are definitely not alone in this!!!! :)

Now, in terms of strength training. It depends on how intense you get. If you reach anaerobic levels then I've read that it can actually increase your BG slightly. But for me again, I don't think that I do strength training at an intense enough level to have that happen.

I would definitely recommend keeping a record of your insulin levels, exercise patterns and carb intake. Then bring them to your next endo appt. and you guys might be able to find some patterns so that you can exercise without fear of going low (or spending a day dealing with low BGs after a workout). Have you ever looked into getting an insulin pump? For me, it's a lifesaver. I see you're from Canada...not sure how easy it is to get one up there, but I met a woman from Mt. Sinani Hospital in Toronto and she told me that it was getting easier.

Here's a link to a good article written by some guys from Canada!:

Hope that helps! You'll figure it out--and check out the Triathlon Team Blog...there's a whole group of women who are sharing their experiences with diabetes and intense exercise!

Posted about 11 years ago
Posts: 0
Hi there!
A great resource is the book The Diabetic Athlete by Shari Archer... it helped explain why for a few years, after intense cardio exercise my blood sugars went crazy HIGH (this is not a super common thing, but it can be explained physiologically)

also, Laura mentions that when one does anaerobic weight lifting, it can slightly raise blood sugar levels...actually, it can DRAMATICALLY raise blood sugar... it just depends on your body, how hard you're working out and such. The book the Diabetic Athlete explains this in fairly great detail.

The other cool place to go for more information is to Diabetes Training Camp ( Quite a number of us on the DiabetesSisters Triathlon Team have attended this camp and it's a wealth of information about exercise and living with diabetes.

Keep working out! It's worth figuring it out!!!
Posted about 11 years ago
Posts: 0
The Diabetic Athlete is a GREAT book. Just wanted to make one correction's by Sheri Colberg.

Good luck!
Posted about 11 years ago
Posts: 0
What a great article! Thanks for posting it. I will also look into ordering the book from amazon or indigo. It sounds like a good read.

I haven't had time yet to explore or fully investigate either website - or I will do this in the next few days ... hopefully!
Posted about 11 years ago