Back to Sports Corner Smart Pumps and Sports: Using Temporary Basal Rates

This Sports Corner Column will feature different aspects of insulin pump therapy and sports participation. Through short, concise articles, one particular aspect of pump therapy and its relationship to sports activity will be discussed. For athletes, performance will suffer if blood sugars are too low or too high. For optimal performance, it is important to balance the amount of insulin and carbs for sports participation. Both are critical to fueling the body for energy. This article will discuss the use of a temporary basal rate around sports participation.

Basal Rate

A basal rate is the amount of insulin a pump delivers over a 24-hour period. When basal rates are set correctly, blood sugars should be in a normal range between meals and overnight. Theoretically, one should not have to eat throughout the day but have blood sugars in a normal range. Most pump users have two to five different basal rates over a 24-hour period to allow for insulin needs at different times of the day. A pump user can decrease the basal rate from 0 to 100% for aerobic type sports. There are three ways to accommodate for the drop in blood sugar often associated with aerobic type of sports. One way is to decrease the amount of insulin, another is to increase the intake of carbohydrates, and the third is to do a combination of the two. When reducing basal insulin, the rate of reduction will depend on factors such as intensity, duration, and mode of exercise. A basal rate can be reduced prior to, during, and after exercise depending on the situation. A few scenarios outlined below will give you an idea of what works for some athletes.

Reducing Basal Rates Prior to Participation

In order to decrease insulin levels during sports participation, it is best to implement a reduced basal rate at least an hour and half prior to the start of exercise. This reduced rate is recommended because the fast acting insulin most often used in an insulin pump (Humalog or NovoLog) peaks about an hour and half after it enters the body. If problems arise with low blood sugars shortly after the start of exercise it may be due to not starting a temporary basal rate soon enough. A good starting point may be to reduce the basal rate by 50% about 1-1/2 to 2 hours prior to the start of competition. Of course, other factors may influence this decision such as if blood sugar levels are too high or if enough carbs are consumed to cover the exercise and potential low blood sugar.

Reducing Basal Rates During Participation

Most pump users who use a temporary basal rate use the same rate for the entire duration of the exercise. For activity that lasts more then an hour or two, this is more prudent. Some athletes struggle with high blood sugars just prior to athletic competition due to the anticipation of an important game. The mental stress can cause a release of hormones (i.e., adrenaline) signaling the liver to release glucose. Once the game starts and the athlete feels less anxiety, high blood sugars often are not a problem. This scenario often creates a dilemma on how to handle an unusually high blood sugar. The first thing to do is to drink water, which will help eliminate possible ketones in the blood and aid in bringing down the blood sugar. If insulin is used to bring down a high blood sugar, it should be done with caution since the activity can speed up the action of the insulin.

Reducing Basal Rates After Participation

By far, more athletes struggle with low blood sugars after exercise than prior to or during the activity. The timeframe involved after exercise is relative because so many factors are involved which can change a situation. Every one is different but many individuals may need less insulin for a period after exercise. This is due to a "lag effect" where the liver and muscles cells are replacing glycogen (the stored form of glucose) -- frequently a 24-hour process. Low blood sugar several hours after exercise is often due to this "lag effect". There seems to be a higher incident in the 4-6 hour timeframe for many athletes but it can be up to 24 hours. The liver and muscle cells are "stealing" glucose from the blood in order to replace the glycogen used for the activity if food is not consumed.

Using a temporary basal rate after exercise on your pump is another way to adjust for exercise. This is an easy to use feature, and handy, if you have not set up a separate exercise basal program or if you have an unplanned exercise event. It simply will reduce your basal delivery by a percentage over a period of time, for example: a 50% decrease in basal delivery for 6 hours.

As mentioned above intensity, duration, and type or mode of exercise can affect how much insulin is needed over the next 24 hours. Most athletes will vary their intensity and duration due to how many minutes they play in a game, how tough the competition is and whether it is a single game or tournament over a couple of days. Many athletes have more problems controlling blood sugars with tournaments that are over a two-day period. If glycogen stores are not replaced in a timely manner (ideally within 30 minutes of a game) or adequately (15 grams of carbs for every 30-60 minutes of activity) it is harder to keep blood sugars up for competition on the second day.

A technique to try with the healthcare team's approval is the rate of perceived exertion after participation. On a scale of 1 to 10 (1 is at rest and 10 is total exhaustion) rate the perceived exertion of the activity as low, moderate, or intense. A low perceived exertion of say 3 on the scale may require a 50% reduction of basal insulin over 6 hours. A moderate rate of perceived exertion of 6 on the scale may necessitate a reduced basal rate of 50% over 12 hours. An intense rate of perceived exertion of 9 on the scale may need a 50% reduction over 24 hours. The only way to determine what works best is trial and error while checking blood sugars frequently. Certainly these techniques will vary from athlete to athlete and the percentage may change (i.e., 50% to 30%) rather than duration depending on blood glucose levels.

Most pump users do not use advanced features and temporary basal rates are no exception. To maximize athletic performance using a temporary basal will go a long way to help athletes with diabetes perform to the best of their ability.

Rick Philbin, MBA, M.Ed., ATC

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Last Updated: Friday September 07, 2012 11:14:52
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