From Virginia, USA:
I have type 1 diabetes, and I once noticed a low when I was having exercise-induced muscle cramps, and after treating it, later I ran high. I am curious as to how the formation of lactic acid during exercise would affect the blood glucose during and after exercise. What would cause the formation of lactic acid in a person with diabetes, versus the increased need for glucose that normally occurs with exercise? Are people with diabetes more prone to lactic acid buildup? When a person with diabetes is having muscle cramps due to this, does this mean no glucose is being utilized for exercise at all? When you get lactic acid cramps, can you assume you will have a rapid rise in blood glucose in the next few hours? (Is this really just the same thing as the liver dumping out sugar in response to exercise, only in more scientific terms?)
Lactic acid is a byproduct of "anaerobic metabolism" (without oxygen), created during vigorous exercise when glucose is burned within body cells for energy. High intensity exercise such as sprinting and competitive basketball are examples of anaerobic metabolism. The build-up of lactic acid in the muscle leads to that "burning" feeling that many of us are familiar with. It will also eventually play a role in fatigue. Interestingly, over breathing occurs in heavy exercise as a result of this production of lactic acid (it gets "buffered" in the blood stream and transported to the lungs where it is breathed off in the form of water and carbon dioxide). Muscle cramps are also related to electrolyte imbalance within the muscle, hydration levels, and other elements of fatigue rather than to lactic acid alone.
People with fluctuating blood sugar control or complications of long-standing diabetes can be more prone to elevated lactic acid levels. This is most likely due to associated cardiovascular and circulatory disorders which result in difficulty delivering oxygen to active muscle tissue. When oxygen levels decrease at the muscle, then energy production must switch from "aerobic" (with oxygen) to "anaerobic" (without oxygen) metabolism and therefore lactic acid levels rise. In the presence of kidney or liver disease, lactic acid may rise further as its clearance will be diminished.
Lactic acid released from active muscles can also be converted into glucose and muscle glycogen in the liver in a process called the Cori cycle. Many of the hormones released during high intensity exercise assist in this process and the liver "dumps" glycogen. This is one of the reasons that some people with diabetes may observe high blood sugars and/or increased insulin needs after intense exercise.
Original posting 12 Nov 2001
Posted to Exercise and Sports
Last Updated: Tuesday April 06, 2010 15:09:28
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