Insulin Use and Exercise, Part 3: Insulin Pumps

Insulin Use and Exercise, Part 3: Insulin Pumps

By Sheri Colberg, Ph.D., FACSM

In Parts 1 and 2 of this series, we discussed the use of rapid- and short-acting insulins, as well as intermediate-acting and longer-acting, basal ones.  In this column, we will finally discuss the use of insulin pumps in active individuals.

 Insulin Pumps: Acting More Like a Pancreas

Whether you have Type 1 or Type 2 diabetes, if you use insulin, you may choose to give it to yourself using a specialized insulin pump, which nowadays is about the size of a pager or cell phone. Pumps use a subcutaneous (placed under the skin) plastic catheter through which small, basal doses of quick-acting insulin (usually one of the rapid-acting analogs like Humalog) are continually delivered to mimic normal insulin release by the pancreas. You must program the pump to give bolus doses to cover your food (mainly carbohydrate) intake at meals and snacks. Every three days or so, you also have to change the infusion site by putting in a new catheter to avoid excessive buildup of scar tissue that can compromise your insulin delivery.

The idea behind insulin pump therapy is to provide insulin just like your body would, that is, in small doses all day long, with bigger doses following food ingestion. Although this physiological pattern can be closely mimicked using any of the newer basal or bolus regimens (e.g., Lantus insulin for basal, Humalog or NovoLog for boluses), insulin pumps make the delivery of that insulin easier and they offer more flexibility by allowing the user to change basal rates of insulin delivery at any time during the day (or set up different preprogrammed profiles of delivery). The exercise responses of people who use either basal insulin or pumps are often similar because both regimens attempt to provide basal insulin levels. Pump users, however, can suspend the pump and immediately reduce basal rates of insulin, which is something that injectable insulin users can’t do as easily without planning ahead.

Many insulin pumps are now available, and the features vary by manufacturer and model. Most of the manufacturers’ respective pumps have features like small basal increments (0.05 unit per hour or less), temporary basal rates, menu-driven programming, and various bolus patterns (e.g., normal, extended, and combination). Normal boluses, for instance, give the insulin dose all at once, but extended ones allow a programmed dose to be given over a longer period to avoid peaks and valleys in insulin coverage for foods that are more slowly absorbed; combination boluses simply combine these two strategies for optimal coverage of foods like pizza. At least two even have self-contained food databases or blood glucose meters, and most are now waterproof at shallow depths.

With all these options, deciding which pump to get can be difficult, so you may want to talk to your health care provider after going to each manufacturer’s website or calling them for more information. Some special features of each are listed in table 3.2. Insulin pumps are not for everyone, though, and the choice to use one (or not) should be an individual one. Their use is not optimal for every sport and activity, but they can help by allowing more rapid alterations in insulin levels during most of them.

Table 3.2: Features of Some Insulin Pumps

Exercise, as well as other activities like hot tubbing or vigorous massage, can increase the absorption rate of insulin regardless of where you inject it. As a result, your circulating insulin levels may increase during exercise but then be too low later on, especially with more rapid absorption of rapid-acting insulin analogs, which are normally used in insulin pumps. Although exercise can also increase the absorption of Lantus or Levemir, this effect appears to be less significant.

This column is excerpted from Diabetic Athlete’s Handbook (released November 2008 from Human Kinetics), which contains essential exercise-related information and examples for Type 1 and Type 2 diabetic exercisers. Look for it in stores or find links to places to buy it online on www.shericolberg.com, along with additional information.

www.diabetesincontrol.com