Most of us know that exercise lowers blood sugar levels—except when they go up instead. How can that be?
In most cases the food that we eat is converted to more glucose than we can use for energy at the moment when we are eating. So the excess is stored for use later. Some of this is in our blood, available for immediate demands, but about 80% of the excess is stored in our muscles and organs, and can be drawn on directly as needed, and about 20% is stored in our liver.
When we exercise we use the glucose that is stored in our muscles. If we exercise enough, however, we use that local supply up, and start drawing on our blood sugar for exercise. So the first effect is that exercise lowers blood sugar. Depending on our glucose level prior to beginning our activities, that blood glucose will fuel our energy demands for a longer or shorter period.
If we go long enough, and don’t have any new input of glucose from eating, our blood sugar will drop lower and lower. When it gets to somewhere around 55 or 60, our hormones signal our liver to start releasing the glucose stored there into our blood. In effect the liver acts as one end of our blood sugar thermostat, the other end being our pancreas, which releases insulin when blood sugar starts going too high.
Up to this point this is totally normal biology, but remember that we have diabetes. When the diabetic liver goes into action, a couple of things can go wrong. The trigger might come too soon—glucose is released when we hit 100 rather than 60. Or too much glucose is released, or the normal accompanying release of insulin that helps us use the glucose for energy is stalled or minimized. Any of these can result in higher blood glucose.
Note that this would be more likely in the morning when we are often subject to rising glucose numbers until we eat, even without exercise, due to dawn phenomenon...
The good news is that this effect of exercise is temporary. The storage of glucose in our muscle cells has been depleted and our bodies will seek to rebuild that reserve. This can take up to 24 hours maybe even longer in some cases, depending on the duration and intensity of the exercise or activity. And where do the muscles get that glucose from? From the blood, so that exercise ends up lowering blood sugar for quite a long period following exercise, even when the initial result may be higher.
The strategy to avoid that temporary high from exercise is quite simple—avoid going so low that your blood sugar rebounds. Keep the liver on the sidelines. So if your blood sugar is below a certain level, have a snack before exercise. If the exercise goes on for an extended period, have a few more carbs every so often. Somebody developed a chart that has carb recommendations based on starting blood sugar levels, intensity, and duration of exercise. The specifics may or may not be right for you, but the concepts are pretty basic and summed up by looking at the chart, which you can find HERE
http://www.dietsite.com/dt/Diets/Diabetes/DiabeticSnacksBeforeExercise.asp
Morris
Diagnosed Type 2, with an A1c of 11.4 in 2003; averaging a 5.0 A1c since then with diet, exercise and Glipizide XL + meds for blood pressure and cholesterol. A bit dated, but scroll down on this page if you want to know more ...
