Diabetes in Endurance Athletes

In diabetics, regular exercise and becoming physically fit is an effective way to help manage your blood sugars and help prevent many of the chronic health problems associated with diabetes.

All of us to some degree understand that life is a balancing act.  There are obligations such as work, friends and family that we are constantly trying to keep in balance with numerous other things that we do it our lives.  For those who are not diabetic, in addition to the above, imagine now, trying to keep your blood sugars in their normal range and realizing a mistake in either direction (too high or too low) can lead to disastrous consequences. That is what it is like to be diabetic.

Exercise can add another level of complexity to that already difficult balancing act.  However, if we start viewing exercise as a medicine to control our diabetes, some of that complexity goes away.  Exercise just like any other diabetic medicine at first glance may seem to act in an unpredictable fashion but once we understand how it affects our bodies, it turns out that it actually works in a pretty straight forward way.

As a diabetic it is important to understand the variables that affect blood glucose response to exercise. Now let’s spend sometime discussing some of the most important ones.

Blood sugars at start of exercise:  Think about postponing exercise if your fasting glucose levels are greater than 250 mg/dl or less than 100mg/dl (have a carbohydrate snack to get it above 100mg/dl)

Time of exercise: Early morning (pre-meal) exercise tends not to drop your blood sugars as much as later-day (after meal) exercise so planning for this can be important

Training status:  Nothing takes the place of experience.   Whether you are a newbie to diabetes, endurance training or both, take it slow!!  A newbie’s blood glucose levels will drop a lot more for a given amount of exercise compared to a seasoned athlete.  This should be a surprise at all, the better trained you are the less energy you use, the less of a drop in your blood sugars you will experience.

Type of exercise you do (and exercise intensity and duration):  This can get a little complicated.  Generally, exercise requires energy which means utilizing blood glucose, which obviously, without replenishment, will lead to hypoglycemia.  The one caveat seems to be highly anaerobic (sub-maximal or maximal) exercise.  Highly intense exercise (such as a time trial) causes the release of several hormones that increase the production of glucose by your liver (e.g. glucagon, norepinephrine) and decrease muscle utilization of it (epinephrine, cortisol, growth hormone).  This can lead to an immediate and large rise in your blood glucose  which can last for a while.  However, once the activity is over and the effects of these hormones wear off, you may experience a precipitous drop in your blood glucose as your body is busy building muscle and liver glycogen used up during your intense activity.

The effects of any oral glucose-lowering meds or insulin that you take: Remember; think of exercise as a medication.  With this being said, it is important to understand how exercise will interact with your other meds. In general, you will likely need to lower the doses of your meds if you take them prior to exercise, but this can be variable and depends on many other factors (type of exercise, duration, recent meal, composition of meal, basal insulin levels, time of last exercise, did your glycogen stores get adequately repleted since your last exercise session? etc..)

Using a Sports Drink:  I am amazed at how often I am asked: I am diabetic, is it safe to use a sports drink and if it is, which one?  Diabetic or not, if you exercise long enough without having some exogenous source of carbohydrates coming in, you will crash.  And just like anyone else, you need to maintain proper hydration, and at some point (with longer duration events), you will need to start thinking about replacing your electrolytes.  Is there one sports drink that is better then another?  Probably not.  Find a sports drink you like, experiment with it, and learn how it meshes with your body.

It might seem overwhelming to have to think about all these variables when you exercise, but as a diabetic you are already accustomed to dealing with how various factors affect your blood sugars. This is no different.  So by understanding how exercise will affect your blood glucose levels, and how your blood glucose levels affecting our ability to exercise, you can train smart and there is no limit to what you can accomplish.

-Dr. Sal (The Raw Cardiologist)