If you regularly do cardio (like running, swimming, dancing etc.), you have probably noticed that your blood sugar reacts differently depending on the type of cardio. While steady-state cardio will usually make your blood sugar drop, interval training can make it increase (you can read why in this post).
The same goes for resistance training (weight lifting) and blood sugar. Some types of resistance training will make your blood sugars increase!
In this post, I’ll talk about how different types of resistance training affects your blood sugar and the strategies you can try to proactively manage your blood sugar during and after resistance training.
I absolutely love resistance training for three simple reasons:
- Resistance training makes me feel strong and empowered.
- Resistance training has helped me shape my body to my liking.
- Resistance training ultimately makes my diabetes easier to manage, as it improves my body’s ability to utilize insulin.
Resistance training generally falls into two categories
- Low-rep (heavy) training with pauses between each set.
- High-rep training or supersets with little rest between sets. Your heart rate is elevated throughout the workout.
Each type of resistance training will affect my blood sugar a little differently during my workouts but they both have the same long-term benefit of a significantly improved insulin sensitivity.
How high-rep resistance workouts affect my blood sugar
In general, I need to be a little more careful and watch my sugars more closely if I do high rep workouts, supersets, or a lot of compound leg exercises (like squats, deadlifts, or lunges). These kinds of workouts will have a cardio-like (aerobic) impact on my blood sugar since my heart rate will be elevated for most of the session and I can expect my blood sugars to drop.
I treat sessions like these almost as I would treat steady-state cardio – by reducing my pre-workout bolus by about 30%-50%.
How low-rep resistance workouts affect my blood sugar
When it comes to more traditional resistance training with fewer reps (less than about 12 reps per set), the situation is a little different. When doing workouts like this, I sometimes see my blood sugar go up, and sometimes I don’t see much of an impact at all. It basically comes down to what body part I’m training.
For smaller muscle groups like arms and shoulders, my heart rate won’t usually increase that much despite the heavy weight, and my blood sugar will remain stable. If I do heavy chest, back, or leg workouts, however, I’ll most likely see an impact, and it can often be an increase. My body reacts in the same way as when I do an interval cardio workout.
Given this knowledge, I’ll reduce my pre-workout bolus minimally or not at all for a low-rep workout, depending on the body parts I am training.
How to prepare for resistance training and prevent post-workout lows
When it comes to resistance training, pre-workout meals play a huge role in whether you’ll be successful in the gym. I always eat something before and after a strength-training workout to make sure I have enough energy to do the workout, to rebuild my muscles, and to maintain good blood sugar levels.
My pre-workout snack is a fairly low glycemic carb (like brown rice) and some lean protein (like chicken breast) which I eat about an hour before my workout. By eating a low glycemic carb plus some protein, I get enough energy for my workout without having to take a lot of insulin.
My post-workout snack consists of a low or high glycemic carb with an easily digested protein (like fruit and a whey protein shake).
As mentioned, I generally reduce my bolus amount for the pre- and post-workout meals by up to 50%, especially on high-rep and superset days, due to the cardiovascular (aerobic) component of the workout, which always makes my blood sugar drop. However, taking a bit of insulin before a resistance training workout also has the benefit that it reduces my risk of high blood sugar during the low-rep sessions.
How to adjust your insulin up to 36 hours after a resistance workout
My approach to insulin adjustments for the 24 to 36 hours after I leave the gym is the same no matter what kind of resistance training I’ve done. What happens when you do resistance training is that you create microscopic tears in your muscle fibers, and for the next 24 to 36 hours, your muscles heal and get bigger and stronger. During this period, your muscles need energy in order to heal and that has to come from somewhere, so low blood sugars can easily be the result if I don’t plan ahead.
If I do resistance training less than four times per week, I will typically have to reduce my nighttime basal insulin by up to 50% on the days on which I work out (this is different for every individual, so you need to experiment and track your results to find what works best for you).
If I do resistance training more than four times per week, the increased insulin sensitivity is present all the time and I can simply lower my nighttime basal permanently without having to adjust for individual workouts.
Summary
I find it easier to adjust for resistance training than for cardio, as long as I am very aware of the kind of resistance training I am doing and remember these guidelines:
- High-rep workouts in which your heart rate is elevated will most likely make your blood sugar drop.
- Low-rep workouts that don’t elevate your heart rate significantly (like arms or shoulders) most likely won’t affect your blood sugar.
- Hard low-rep workouts of large muscle groups can affect your blood sugar like an interval workout, potentially leading to an increase in blood sugar.
- Don’t be scared of eating!!! Eat enough lean protein and carbs to fuel your workout, ensure muscle recovery, and (with the appropriate insulin dose) stabilize your blood sugar levels.
- Consider reducing your insulin levels appropriately during the 24 to 36 hours after a workout to adjust for the type of resistance training you’ve done.
Have fun in the gym!
Suggested next post: How to Prevent Low Blood Sugar during Cardio Workouts
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Went for a walk 23 min lifted 3 sets of 10 on my legs and ate oatmeal for break fast.
My sugars 134 upon weakening then jumped To 214 at lunch time check. So confused
Different things could be going on. It could be a one-off, but if you see it consistently you’ll have to develop a strategy for that. If you’re on insulin and reduced that before/during exercise you might need a little extra after. Could be the anaerobic exercise impact (as you read in the article), messy infusion site/injection etc. I suggest you track your BGs for a while and see if this is a reoccurring theme
Since I work a real physical job every day, not living in a gym, I have no major sugar problem like you are saying I should have…? Should I continue doing what I am doing or should I be concerned?
Seth, I’m not sure what you’re asking. If your blood sugars are within range all the time you’re obviously very good at managing them and I don’t see any reason to make changes. All the posts on the website are meant as support but if you don’t need it, that’s not a bad thing
I workout early morning before work and need most days to take a unit or 2 bolus as hormones makes my blood glucose levels rise, I don’t eat breakfast during the week and this works for me.
I’ve been reading a lot lately on how BCAA’s can help with getting your protein intake and can help with insulin sensitivity. Is there any proof of that or have you experienced yourself any of those benefits?
There is a lot of conflicting opinions out there about BCAAs (and the science isn’t conclusive yet) but I belong to the school who think that they don’t make any real difference as long as you otherwise eat a healthy balanced diet. Especially, I have never seen convincing evidence of their effect on insulin sensitivity. But they won’t hurt you, so you can try them for a while to see if they do something for you if you like.
Christel, thank you for the thorough article. I loved your explanation about the mini muscle tears after an intense strength training workout that calls for a decreased nighttime basal up to 50%. Your insight is very helpful to me and many many other T1Ds. Thank you.
Thank you for the feedback, I’m so glad it’s helpful!
Christel,
I have Type 2 diabetes and take oral medication once a day. How do I figure out what types of exercise lower my bs and should eat the same combination of pre and post workout meals as you suggested?
Hi Laura – that great questions.
In general, exercise impacts us the same way. So if you’re looking to lower your BG now cardio is the way to go. Resistance training can improve your insulin sensitivity in the long run, so that’s more of a long term investment.
I would still include a small snack before a resistance training. You can start with a lean protein and small serving of carb (maybe 1-2 rice cakes) and see how it goes. If that doesn’t work for your blood sugars you can consider cutting back on the carbs
Would you please explain what you mean in Summary Item #4, where you state that you should eat enough carbs to “combat exercise-induced high blood sugar levels.” I don’t understand how eating carbs would combat high BG. Or did you mean to say that carbs would combat exercise induced low blood sugar levels?
Hi Susan,
Thank you, that was not well written. I’ve changed it, so hopefully, it makes more sense now. In this specific context, I was referring to the overall benefits of fueling your workouts, adding that the right combination of food and insulin additionally is a way to reduce the risk of highs or lows.
You have no idea how helpful this article and these daily challenges have been for me. I dont know any other type 1 diabetics and finding this information has seriously taken so much anxiety away from me from feeling like im alone. Thank you 🙂
Carly, you are welcome – I’m so glad this is helpful to you!!
I always believed that armed with the right information we can be successful, in pretty much anything. The more we know about what’s going on with our bodies (hopefully) the less anxious we become.
Keep soldiering on