Strength/Resistance training is definitely popular in the T1 athletic community and probably because it just might be the easiest in terms of BG management. To clarify, when I’m talking about this type of training, I mean the type of non-cardio exercise you see most people doing at a gym including using weight machines, barbells, dumbbells and/or resistance bands.
Most T1 diabetics will see either no effect or a slight rise in BGs due to strength training.
Personally, I try to incorporate some strength training a few times per week. I originally started strength training as part of my swim team training but rediscovered it later in life to support my running habit. Before I started doing regular strength training, I was an injury prone runner. Ever since I added in a few days of strength per week, I rarely get injured*. Strength training also has other benefits such as increasing bone density and preserving muscle mass, which we tend to lose as we age**.
Since I often find strength training will have a minimal effect on my blood glucose, I’ll often opt to do my strength workouts in the evening or after my morning cardio. If I’m having a wonky blood sugar day, I’ll often choose a strength workout to minimize the variables affecting my blood sugar.
Unlike a cardio or endurance workout, usually, I don’t reduce my basal at all. I still make sure to have carbs nearby during my workout but I almost never have to use them if all I’m doing is strength training since my blood sugar is more likely to rise than fall. There are a few reasons this may happen.
- First, the way strength training works is you’re actually breaking down your muscles. When you recover and repair themselves, that’s when they actually become stronger. In the process of breaking your muscles down, some glucose is actually released into your bloodstream which may cause your blood sugar to rise. That’s right, it’s not just your liver that dumps glucose into your bloodstream, your muscles do too***.
- Second, any workout where you’re putting out maximum effort may trigger an adrenaline response, (think “fight or flight”). This can cause your liver to dump glucose into your bloodstream so your body is prepared for the “fight or flight” situation.
- Finally, if you’re not eating enough, your body may begin to break down your muscle to use as fuel and this can also cause a rise in blood sugar post workout. This is not only detrimental to making progress in the gym but can also cause another curveball for your blood sugar management.
For those reasons, I tend to monitor the trend on my CGM and if I see my blood sugar start to rise, I correct immediately. If I’m in automode and it isn’t giving me enough basal, I’ll take it out of automode to make sure I’m getting my regular amount or even increase it a bit to avoid a spike. For a strength session where I know I’m going to try to PR my lifts, I might give myself a bit of extra basal (or bolus if I’m already a bit high) at the start of the workout as well. If I’m starting the workout and my blood sugar is in a good place, I’ll usually play with the basal first since it will affect my blood sugar more slowly and incrementally than a correction bolus. I can always put it back to my normal rate or reduce it if I start to see a downward trend. This will take some self-experimentation to figure out exactly how it will affect you personally as how much you might need to (or not need to) adjust.
The other thing I have been known to do is mix up strength and cardio in the same workout. If a strength session is driving my blood sugar up, I will sometimes catch the high by going for a walk, running on a treadmill or hopping on a bike for a few minutes. Similarly, If I’m going low, I have been known to stop my cardio and incorporate a few strength exercises to allow my blood sugar to stabilize and rise again.
Keep in mind other things that can affect your BGs such as hormones for women, alcohol consumed up to 24 hours before, the dawn phenomenon and competition adrenaline. If your BGs aren’t doing what you would expect, be ready to adapt and err on the side of going high. It’s safer and you can always bring it back down with a little insulin later on, if needed. If you accidentally over-correct an oncoming high with insulin, you can always nudge it up later with small amounts of carb to avoid going low.
These are my general rules of thumb but again, the most important thing is to be flexible and adjust as needed. You can cut a workout short if you’re going low or extend it if you’re trending high and have the time to do so. You can eat more or less and adjust insulin levels to stay in range. Play with the variables and find out what works best for you! Also, endurance training isn’t for everyone and there are plenty of ways to stay active if you hate it. More to come in a future post on BG management strategies for other types of workouts!
*The few times I have, it’s almost always because I increased my mileage too quickly and developed an overuse injury. Thank goodness Marty and I are both licensed sports massage therapists and have pretty in depth knowledge of how to properly rehab an injured muscle.
**More can be found on this here.
***More can be found on this here.
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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.