Exercise and I have a love-hate relationship. It’s hard enough to work up the motivation to do it, but I muster up the willpower about three or four times a week by reminding myself that it’s good for me. Or it’s supposed to be anyway. But what if my diabetes were complicating the positive effects of my exercise routine? What if it could actually be making it harder for me to be healthy? Everyone pretty much assumes that exercise helps with diabetes management…but is that actually true for type 1 diabetics? Let me explain.
This fall I have had the opportunity to use the gym facilities at VCU since my husband is taking grad school courses there. When I found out I could get a “plus one” membership to the school’s MASSIVE, fabulously-equipped, state-of-the-art gym, I was thrilled. This place is an exercise fanatic’s dream (not that I am myself an exercise fanatic…). Admittedly, however, I haven’t gotten much use out of my access to this dream facility since I signed up in September…except for the lap pool. Growing up I swam on my neighborhood swim team every summer from age 6ish to age 18. I was never very competitive — I just loved to swim. Part of the benefit of the VCU gym membership is access to a gazillion different types of fun classes, including the Fitness Swim class I enrolled in back in September. I paid an additional $20 to get to swim with a group for an hour three days a week, working primarily on endurance.
I have been trying to stick to this swimming schedule now for about three months and so far I’m very satisfied with the class itself. I feel stronger and I definitely have more stamina than I did in the beginning. However, this swimming program has resurfaced one of my [many] frustrations with diabetes: the challenge of keeping blood sugars controlled during exercise.
In my personal experience, I’ve noticed that cardio exercises like walking, jogging, using the elliptical machine, etc. tend to make my blood sugar drop fairly quickly. Take for example, these blood sugar readings before and after 20 minutes of walking just over a week ago (pay no attention to the time and date on the purple meter…it wasn’t calibrated correctly):
I achieved this reading without taking any insulin during the meal right before our walk. That just goes to show how much more effective my natural insulin production becomes during exercise — but don’t ask me to explain how the physiology of that works!
Swimming, however…well, that’s a different story. My first week of the Fitness Swim class turned out to be an experiment in glycemic control that I hadn’t anticipated. Going into my first session, I prepared by having a light breakfast (I find that if I eat nothing before working out early in the morning it actually makes my sugar go up). I didn’t take any insulin with my meal for fear that I might go too low during the workout. I got to the gym about half an hour after breakfast at 7 am and proceeded to swim. It was very strenuous since I was really out of shape. I decided to do a quick sugar check in the middle of the workout and to my surprise, discovered I was in the mid 200s. What?! I had been working out so hard…how could my sugar be high? I continued with the workout hoping that it might drop. My 2-hour post-breakfast blood sugar check showed I had only a minimal decrease: my sugar was still hovering around 200.
I never have really understood what category of exercise swimming falls into. Is it cardio? Is it strength? Is it both? Is the fact that it’s not-quite-totally-cardio the reason why I’m having trouble keeping my sugars in check? Wanting a fellow diabetic’s perspective, I posed a question in a diabetes forum on MyGlu.org to see if other T1 diabetics had experienced this problem and could explain to me (in layman’s terms) why this was happening. The best answer I received was this:
what I have been told is that “anaerobic exercise” like weight lifting because of the muscle constrictions back and forth raises it because of the hormones going through your body and aerobic lowers it…but that is just what my doc says. I used to always go low running or swimming before starting to weight lift so now I do lifting first at the gym and then cardio…it helps =)
Posted by “Banana”
Anaerobic versus aerobic exercise…hmm. Funnily enough, I’ve been studying aerobic versus anaerobic cellular respiration in humans in my biology class this semester. I decided to do some more investigation on this topic and found a great article which helped me understand the differences between anaerobic and aerobic exercise and their effects on people with type 1 diabetes. Although the article is focused on the benefits of continuous glucose monitoring (CGM) technology, its explanation of the anaerobic vs. aerobic issue is very thorough. Basically, the article confirms Banana’s simplistic explanation:
Control of glucose homeostasis [in non-diabetics] during exercise is dictated by a complex interaction between multiple hormonal regulators (e.g., insulin, glucagon, catecholamines, and glucocorticoids), the nervous system, and various molecular regulators within skeletal muscle and liver, allowing for precise control of glucose concentration during most activities. In persons with type 1 diabetes, however, control of glucose homeostasis during exercise is extremely challenging, as insulin levels cannot change rapidly in response to exercise, and there may be deficiencies or exaggerations in other hormonal responses.8 As a result of a variety of unpredictable factors, exercise may cause either hypoglycemia or hyperglycemia in persons with type 1 diabetes… The wide ranging glycemic responses among individuals appears to be related to differences in pre-exercise blood glucose concentrations, the level of circulating counterregulatory hormones and the type/duration of the activity.
J Diabetes Sci Technol. 2009 July; 3(4): 914–923.
Not only are the effects of exercise on blood sugar dependent on the type of exercise, but also the impaired hormones which respond (or don’t respond) to the stress on your body; the starting blood glucose level; stores of sugars in muscles and the liver; and the duration of activity. Jesus. All I wanna do is swim for one hour every other day. Is that so much to ask?
Of course, I refuse to let my biological inadequacies prevent me from doing an activity I love. My method for preventing hyperglycemia (high blood sugar) after swimming thus far has been to: a) eat a snack before working out…usually a Luna protein bar which has about 19 g of carb, and b) increase my normal insulin to carb ratio to account for the rise in my blood sugar during the swimming. Thankfully, that seems to be working fairly well. This morning I didn’t test my pre-exercise sugar (whoops!), but I ate my Luna bar and took three units of Humalog (fast-acting insulin) and my sugar was 117 mg/dl two hours later. I do notice that when I do this, however, I sometimes have hypoglycemia (low blood sugar) a couple of hours after I exercise, forcing me to eat another mid-morning snack and my sugars tend to be lower throughout the entire day afterward. This phenomenon, called “late-onset postexercise hypoglycemia” in that article I cited, “may last for at least 24 hours” after exercise!
As if the hyperglycemia wasn’t bad enough, now I have to worry about going low for potentially an entire day after exercising. No wonder I can’t lose any weight…I’m always starving and trying to compensate for my low blood sugar by eating every couple of hours! Diabetes presents a huge challenge when it comes to exercise. On the one hand, it almost feels like I’m sacrificing my diet to get exercise because I’m constantly hungry. On the other hand, I’m always playing a guessing game about how much insulin I need to take before exercise and how it will affect me. Will I go high? Will I go low? I’m exhausted just thinking about it.