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Pumper’sVoice

Overcoming the Challenges of Physical Activity

Swimming. Gardening.  Evening strolls.  Whatever activity you prefer, adjustments will be necessary when you have diabetes and use an insulin pump.

Preventing Hypoglycemia
 
With increased physical activity, muscle cells become much more sensitive to insulin.  This enhanced insulin sensitivity may continue for many hours after the activity has concluded.  The more intense and prolonged the activity, the longer and greater the enhancement in insulin sensitivity.  To prevent low blood sugar, one can reduce insulin, increase food, or do a combination of both.

It is not usually enough to just “shut off the pump” or “disconnect” during physical activity.  Eliminating basal insulin during the activity will not have much affect on the level of insulin in your bloodstream for at least an hour.  When exercise is going to be performed within an hour or two after a meal, the best approach is usually to reduce the mealtime bolus.  Since both aspects of the bolus (the part given for food and the part given to cover an elevated blood sugar) are affected, both need to be reduced.  To accomplish this, use an activity “multiplier”:  calculate your mealtime bolus as usual (based on the food and the blood sugar level), and then multiply the bolus by a factor that results in a lower dose:

Activity
Multipliers

Short Duration
(15-30 minutes)

Moderate Duration (40-60 minutes)

Long Duration
(>60 minutes)

Low intensity

.90

.80

.70

Moderate intensity

.75

.67

.50

High intensity

.67

.50

.33

For example, a moderate-intensity workout performed for 45 minutes may require a 33% bolus reduction (thus the .67 multiplier). 

When exercise is going to be performed before or between meals, reducing the bolus at the previous meal would only serve to drive the pre-workout blood sugar very high.  A better approach would be to take the normal bolus at the previous meal, and then snack prior to exercising. 

The amount of the snack depends on the duration and intensity of the workout.  The harder and longer your muscles are working, the more carbohydrates you will need in order to maintain your blood sugar level.  And the bigger you are, the more fuel you will burn while exercising.

There is no way of knowing exactly how much you will need, but the chart below should serve as a safe starting point.

 

Carbohydrate Replacement Per 60 Minutes of Physical Activity

 

50 lbs (23 kg)

100 lbs (45 kg)

150 lbs (68 kg)

200 lbs (91 kg)

250 lbs (114kg)

Light Activity

5g

10g

15g

20g

25g

Moderate Activity

10g

15g

20g

25g

30g

Intense Activity

15g

25g

35g

45g

60g

For example, someone weighing about 150 lbs who is doing 90 minutes of light housework should consume about 22g of carbohydrates (15g x 1.5 hrs).  Someone weighing 200 lbs who is running for 30 minutes should also consume about
22 g carbohydrates (45g x .5 hours).

The best way to fine-tune your workout snack is to test your blood sugar before and after the activity.  If it holds steady, you are consuming the right amount.  If it rises, cut back on the number of carbs.  If it drops, add some more next time. 

For prolonged activities (lasting two hours or more), you may also need a reduction in your basal insulin.  A good starting point would be to set a temporary basal rate of 50%, starting an hour prior to the activity.  That way, when the activity begins, the level of insulin in your bloodstream will already be on the decline.

Anaerobic Exercise and Competitive Sports

It is not unusual to experience a blood sugar rise at the onset of high-intensity/short-duration exercise and competitive sports.  This is caused by a surge of adrenaline that counteracts the effects of insulin and stimulates the liver to release extra sugar into the bloodstream.  Examples include weight lifting, martial arts, sprints, and events where performance is being judged or winning is the main objective.

If you notice that your blood sugar rises during these types of activities, it is in your best interest to take extra insulin an hour or so beforehand.  To determine how much, consider the average rise that you experience, divide it by your sensitivity (correction) factor, and take half that amount.  For example, if you rise 100 mg/dl when lifting weights and each unit of insulin normally lowers you by 25 mg/dl, take 2 units before lifting. 

Delayed Effects

Many aerobic activities (particularly those that are long or intense) and some anaerobic exercises cause blood sugars to drop several hours later.  We call this Delayed Onset Hypoglycemia. 

If you find that certain activities lead to a blood sugar drop several hours later, try lowering your basal insulin by 20-30% for several hours; having an extra snack; or reducing the bolus given to cover the carbs consumed at the meal or snack following the activity.

Pre-Activity Highs

It is not usually dangerous to exercise with a high blood sugar level, as long as you are well hydrated and there is some insulin in your body.  Without a minimum level of insulin, exercise will cause the blood sugar to rise further and may accelerate the production of ketones—acidic by-products of fat metabolism.  If ketones build up in large amounts, they can alter the delicate pH balance in the bloodstream and produce a life-threatening condition called Diabetic Ketoacidosis (DKA). 

If your pre-exercise blood sugar is inexplicably high, there is one way to make sure you have sufficient insulin to allow for a safe exercise session:  check for ketones.  The presence of ketones in the urine indicates a lack of insulin in the body.  Do not exercise if you have ketones in your urine.  Instead, drink plenty of water and follow your physician’s advice regarding insulin dosing. 

If you do not have ketones and your blood sugar is just moderately elevated, it should be safe to exercise.  However, high blood sugars during exercise can be a problem for anyone who wants to maximize their performance.  Be sure to consume extra fluids before exercising to compensate for the loss of fluids through both urine and perspiration, and cover the high blood sugar with half the usual correction bolus.

Disconnecting for Exercise

A woman jogs around a track.Everyone who wears a pump has run into situations where it is desirable to simply disconnect—particularly during sports that involve rough contact, harsh movements or exposure to water.  How, then, can it be done safely and effectively? 

One of the keys is to limit the disconnection time to no more than an hour or so.  Prolonged disconnection, even during & after exercise, can result in a dramatic blood sugar rise and production of ketones.
 
Disconnecting for less than 90 minutes rarely presents a problem in terms of blood sugar control.  It is not usually necessary to replace the missed basal insulin.  However, if you feel the need to disconnect for more than 90 minutes, try hooking back up to your pump each hour, and bolus an amount equal to about 50% of your usual basal rate.  For example, if your usual basal rate is .6 units/hr and you would like to disconnect all afternoon for an extended hike, bolus .3 units before disconnecting and then reconnect each hour and administer a bolus of .3 units.

Wearing The Pump During Exercise

A number of good options exist for wearing the pump during exercise.  If the standard clip will not hold the pump in place well enough, consider using a Sport Pack from Unique Pump Accessories.  The Sport Pack is a tight fanny-pack made of spongy neoprene material, sized perfectly for the pump.  Unique also offers spandex belts with pump-sized pockets that fit securely around the arm, thigh or calf.  These are called the Thigh Thing and the Leg Thing.

Pump Wear Inc., another pump accessory company, offers the Pump Band: a popular belt that holds the pump around the arm or leg, similar to an I-Pod holder.  For waterproofing the pump, check out the waterproof microphone case by Aquapac. It’s designed for small electronic items and has a pass-through port for the pump tubing to come through.  The clear flexible casing allows the pump to be programmed while sealed inside.

(Pictures and descriptions of all these items are at my Web site www.integrateddiabetes.com, and may be ordered by calling 877-735-3648.)

Infusion Set Issues

Many people have difficulty keeping their pump infusion sets in place when exercising.  Perspiration and rapid movements can cause the set to come loose.  One of the best strategies for avoiding this problem is to wear the set in a place where the skin is not oily and does not move/stretch too much; where perspiration is minimal; and where there is a tight garment covering the infusion sight:  The buttocks. Athletes and weekend warriors alike usually find that the infusion sets hold in place much better on the buttocks than any other part of the body.

It also works to put extra tape such as IV-3000 or Tegaderm over the infusion set. Cut a hole in the center of the tape before putting it over the set so that the connect/disconnect mechanism will still work. If adhesion problems persist, Mastisol solution (from Ferndale Labs) may be your last resort. This “super glue for the skin” is certain to hold the set in place. In fact, the stuff is so strong, that you might need “Detachol” solution (also from Ferndale Labs) to get it off!

Get Up and Get Moving!

So there you have them: strategies for managing your blood sugar, wearing your pump, and keeping your infusion set in place for exercise.  So lace up your sneakers and enjoy yourself!            

 

About the Author

Gary ScheinerGary Scheiner MS, CDE is a diabetes educator with a private practice (Integrated Diabetes Services) near Philadelphia, and author of Think Like A Pancreas: A Practical Guide to Managing Diabetes With Insulin. He has had Type 1 diabetes for 20 years, and offers diabetes education and management consultations via phone, fax, and Internet to patients throughout the world.  Submit inquiries to  gary@integrateddiabetes.com, or call (877) SELF-MGT.