By Sheri R. Colberg, PhD, FACSM
Whether you have type 1 or type 2 diabetes, if you use insulin, you may choose to use a specialized insulin pump for both your basal and bolus insulin delivery (1). Pumps have a small catheter placed under your skin and are programmed to cover your basal insulin needs by delivering small doses of fast-acting insulin to mimic normal insulin release by the pancreas. Insulin pumps are programmed to deliver small, basal doses of fast-acting insulin to mimic normal insulin release by the pancreas throughout the day. These pumps are not ideal for everyone, and the choice to use one should be an individual one.
The goal of insulin pump therapy is to provide insulin just like your body would—that is, in small doses all day long, with bigger doses after meals. Although this physiological pattern can be closely mimicked using injection regimens (e.g., Levemir for basal and Apidra boluses), insulin pumps make delivery easier and offer more flexibility by allowing you to have different basal rates of insulin delivery during the day or use temporary basal settings (such as during and after exercise). Pump users have the luxury of suspending the pump or immediately reducing basal delivery of insulin for activities, which you cannot do as easily without planning ahead if you use injections.
Although the number of insulin pump companies has dwindled recently, a number of pumps with various features are still available. Although you still have to be smarter than your pump, these “smart pump” features have helped take a lot of the guesswork out of it. Most pumps have options for small basal increments (0.05 unit per hour or less), temporary basal rates, insulin-on-board calculators, menu-driven programming, and various bolus patterns. Normal boluses, for instance, give the insulin dose all at once, but extended ones allow a dose to be given over a longer period to avoid peaks and valleys in coverage for foods that are more slowly absorbed; combination boluses combine these two strategies for optimal coverage of foods like pizza. Some are waterproof at shallow depths. The race is on to create the best combination insulin pump therapy and continuous glucose monitoring (CGM) with algorithm-driven control systems. These “closed-loop” systems integrate features and make decisions for you, although exercise remains a sizeable management hurdle to overcome.
Insulin Pump Exercise Strategies
Insulin pumps give users the opportunity to reduce basal insulin levels and/or bolus doses in desired amounts and for different durations. As a result, pump use may reduce your exercise-induced hypoglycemia risk compared to multiple daily injections. Some strategies using pump features may be helpful, based on the purpose and timing of insulin dosing (1).
Altered Bolus Doses Before Exercise: You can adjust your meal and correction doses of insulin with a high degree of accuracy to accommodate for exercise. Calculate boluses as usual (entering the actual carbohydrates and blood glucose) and then adjust them using a percentage. For postmeal activity (i.e., when bolus insulin is still peaking, such as within 2 hours after eating), reduce your meal bolus by 25, 33, or 50 percent, depending on your upcoming activity.
Lower Basal Rates During Exercise: Reducing your pump’s basal rate before, during, or after exercise by programming a temporary basal rate can allow you to eat less to compensate and prevent lows, particularly when exercising for 2 hours or more. If you can plan ahead, try reducing your basal rate somewhat starting 1 to 2 hours before exercise to make sure your insulin levels are lower when you begin. Try reducing it by 50 percent, although you may need to lower it by 80 percent for prolonged exercise.
Lower Basal Rates After Exercise: Lowering your basal insulin for a time after exercise can also keep you from getting low later when your muscle glycogen is being restored. How much you will need to reduce it will vary by person and by situation. A common starting point is to reduce your basal rate by 25 percent for 6 to 8 hours afterward if you anticipate possibly getting low later.
Alternate Basal Insulin Profiles: You can use altered delivery patterns if you are going to be doing a full-day activity, such as during summer camp, or while engaging in intense sports conditioning, or when completing major projects around your home. Pumps allow you to switch to a basal pattern that is entirely different from your usual one, allowing for significant delivery rates during peak activity and more modest reductions when you are resting afterward. If you have a pump that allows you to alter bolus calculation formulas along with basal settings (insulin delivery profiles), such as the Tandem pump, you can also use a lesser hyperglycemia correction factor, decrease your insulin-to-carbohydrate ratios, and raise your target glucose during times when you will be more insulin sensitive.
Challenges to and Solutions for Pump Use During Exercise
Insulin pump use does present its own set of challenges related to physical activity and sports. For instance, some athletes have issues with getting infusion sets to stay in place during certain activities or with excessive sweating. Others have complained that the pump or tubing simply gets in the way during exercise, and they may prefer to remove the pump entirely while active. Given that pumps deliver rapid-acting insulins only, removal of the pump for an excessive length of time (longer than 1 hour) can result in severe hyperglycemia and ketone formation, potentially leading to diabetic ketoacidosis (DKA). Exposing your pump to water and extreme weather conditions can also threaten its integrity and the insulin in it.
- Excerpted from Colberg, SR, Chapter 3, “Ups and Downs of Insulin and Other Medications,” in The Athlete’s Guide to Diabetes: Expert Advice for 165 Sports and Activities. Champaign, IL: Human Kinetics, 2019.
Sheri R. Colberg, PhD, is the author of The Athlete’s Guide to Diabetes: Expert Advice for 165 Sports and Activities (the newest edition of Diabetic Athlete’s Handbook), available in early 2019. She is also the author of Diabetes & Keeping Fit for Dummies. A professor emerita of exercise science from Old Dominion University and an internationally recognized diabetes motion expert, she is the author of 12 books, 28 book chapters, and over 400 articles. She was honored with the 2016 American Diabetes Association Outstanding Educator in Diabetes Award. Contact her via her websites (SheriColberg.com and DiabetesMotion.com).