Diabetes and Exercise: The Real Fun and Games

Saturday’s Project Blue November challenge was to show how you keep fit to help control your diabetes.  We all know that being in good physical shape is beneficial whatever your challenges in life.  But I have to laugh when I read that exercise is essential in “helping to control your diabetes”.  I will not deny exercise is good for you, but for a Type 1 Diabetic, exercise can throw a wrench into your control.

 (My dogs help me get in shape by forcing me to walk them daily.  

This view at the top of Mission Ridge is great motivation.)

Whether diabetic or not, how your body reacts to exercise depends on the type of exercise.  Is it intense but for a short period of time, like sprinting?  Is it moderate for a long period of time like walking a dozen kilometres of Mission Greenway?  Is it a combination of two, like playing hockey or soccer where intense activity is followed by periods of rest?  Or is it a hike over terrain where the intensity changes from walking on a level path to climbing a steep grade and back down again?  If you’re a non-diabetic it’s likely the only difference you’ll notice in these activities is how hard you’ll have to work to perform them.  For a diabetic it’s a matter of juggling food, water, and insulin basals and boluses. I guess I should explain how basal and bolus delivery of insulin works for a pump users.  

My pump allows me to set what is called a basal rate of insulin delivery, where every few minutes I receive a very small dose of insulin, just like my pancreas would if it worked.  Because the amount needed can change over the day, I’m able to set different rates at different times of day.  For example at 8:00 a.m I received .800 units per hour, and at 11:00 I start receiving .850 units per hour.  A bolus dose is insulin that’s taken when you’re about to eat a meal or snack, or when you test and discover your blood glucose (BG) level is higher than your desired goal.  

 Long ago I figured out my personal Insulin Carb Ratio (I:C)  and my Insulin Sensitivity Factor (ISF) and these are programmed into your pump when you first set it up.    Now when I eat some carbs, I test my BG level using my glucometer and input the number of grams of carbs I’m about to consume.  Using my current BG reading, my I:C and ISF, the glucometer then calculates the amount of insulin I need.  The pump requires you to input that number into the pump, press OK and in it goes.  Right now, I have a pump that is connected to my glucometer remotely, so I can just input the number on my glucometer and it transmits the info to the pump, which puts then puts the insulin in my body. (I borrowed the above photo from the blog Active Diabetic, An Ongoing Experiment. My pump is similar, his is the next generation Animas Vibe.  I hope to upgrade to it very soon.) 

There are certain rules to be followed when it comes to setting these basals and boluses and there are certain rules to think about when it comes to exercise, but the reality is that it’s much like “The Pirate Code”.  And they can vary greatly from person to person.  I’m just going to talk about hiking, ‘cause that’s what I like to do.  Near the start of a long hike, glucose supplies 80% of the fuel required.  Your body uses glucose that’s already in your blood, it’s available from the interstistal fluid around your cells and your muscle cells have glycogen stores from which they withdraw glucose.  After three hours, half of the fuel comes from glucose, the other from fat.  After six hours, almost 80% of fuel will be derived from fat.  

So one part of preparing for exercise is to reduce the amount of insulin you take, because if your insulin uses up the glucose, then you’re going to have a hypoglycemic reaction.  You can do this by using the Temp setting on the pump to temporarily lower your basal for a set amount of time, and you can take less insulin when you bolus for eating. Your body does need some insulin to get the glucose into yours cells.  And if you lower it too much, then you can end up with high BG levels, which can make activity challenging and cause problems with lung function. I aim for a BG between 5 and 6.5.   If your BG is over 14, for some reason your body will actually start dumping glucose into your system from your liver if you exercise, so if you hit 14 you need to bolus and wait for your BG to drop.  

In terms of carbs, you need to figure out what kind are the best to take.  You need to have fast acting carbs (dextrose, jelly beans, juice) on hand for sudden drops in BG, and you want to consume some slow acting carbs before you start your hike, and small amounts every hour or so when you’re doing a hike that’s more than a couple of hours (granola bars, power bars, fruit).  

When we hiked the Rim Trail at Cathedral Lakes Park, the info showed us the hike would take 7-8 hours with an elevation change of 500m.   This required a lot of supplies.  In my large back pack, I packed a big lunch with two sandwiches, cookies and fruit.  For low blood sugar I added two drink boxes, two granola bars, and three tubes of dextrose tablets.  I packed extra insulin and pump supplies and batteries in case my pump failed in any way.  And of course I had my cell phone and camera.  We also carried a Spot GPS locator.  Not because we were worried about getting lost, but in the rare instance that I might have some sort of distress that would prevented me from hiking and require a rescue if food or insulin ran out.

After a lot of trial and error you figure out what works best for you in terms of how much to lower your basal and bolus and how much extra carbs to consume.  And here’s the fun part.  The less “trained” you are for a particular activity, the more you need to lower your basal and bolus doses to keep from going low, because your body is working harder when you’re not in prime shape, so it will use more glucose.  Therefore as your activity improves your fitness level, your body won’t have to work as hard.  It will use less glucose and therefore as you get in better shape, so you have to adjust your basal, bolus and carb intake all over again.  Fun!  

To add some more fun, your muscles like to keep their glycogen stores up for future activity, so after  strenuous exercise, they steal glucose from your blood to replenish its depleted stores.  As a result you need to keep a close eye on your BG levels by testing more frequently for a day or two after a particularly strenuous event, like a hike or a marathon.  On the first couple of days following our big hike, I took very little insulin over the next two days and had normal BG levels.  It’s pretty awesome to have great numbers over a long period of time.  

So things went pretty well for me over the 8 ½ hours it took to for our hike.  I let myself run a little high to prevent a low, but not high enough that my activity level was compromised.  I did run into a challenge during the last hour and half of hiking. I felt a bit off and tested, only to discover my BG was 11.  I was frustrated because we’d been working fairly hard, hiking up a slope and by all accounts I shouldn’t have been high.  I adjusted my basal, increasing the flow a little and took a very small bolus.  Within about an hour I was feeling low and did a test and discovered I was 3.6.  We stopped, I took a few dextrose tabs and drank some apple juice.  I may have eaten a cookie as well.  While we were waiting for me to return to normal we were joined by a deer, so the timing was serendipitous.  

After my weekend away, I was reading about exercise in the book Pumping Insulin, by John Walsh and Ruth Roberts.  I discovered a possible reason for what happened at the end of the hike.  Turns out dehydration can affect your BG level. Less water in your blood will concentrate it and make the percentage of glucose seem high.  Though we had two camel backs and two bottles of water with us on the hike, we were running low towards the end and though we hadn’t said anything to each other, we were rationing it.  When I stopped to test my BG and had the 11, I was quite thirsty and did drink a fair bit.  It’s likely that as a result, the insulin I added to the mix was more than I needed over the next hour.  In retrospect, I have noticed when I’m struggling a bit on a steep climb, stopping for a drink of water seems to do wonders for my energy level.  It seems there’s always something to learn about managing your diabetes.  Even after 40 years.