Diabetic Athlete

Guidelines for the Insulin-Using Diabetic Athlete


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The exact adjustments of insulin dose and carbohydrate ingestion for exercise must be made on an individual basis and these adjustments must be developed by trial and error. A trial and error approach is successful, because blood glucose responses to the same exercise performed at the same time of day are at least somewhat consistent from day to day in an individual with diabetes. What follows are some specific guidelines for starting this trial and error process and some other useful tips for exercise for insulin using patients:

A. Glucose control before exercise

The blood glucose should be between 100 and 250 mg/dl before beginning an activity.

If the blood glucose is above 250 mg/dl with ketones in the urine or above 300 mg/dl even without ketones present in the urine, then insulin is needed. Wait until blood glucose is below 250 mg/dl to start exercise. If you are not sure how to test for ketones, check out one of the “Sick Day” protocols.

If the blood glucose is below 80 mg/dl, carbohydrate foods or beverages should be ingested to increase blood glucose to above 100 mg/dl.

B. The amount and timing of insulin injected:

One option for preventing hypoglycemia during exercise is to lower the amount of short- acting insulin injected prior to short duration exercise of moderate intensity by 20-30% of the normal dose. An example of a moderate activity would be an easy jog for 20 min at 10 miles per hour. If the exercise is intense and will last longer than one hour, try dropping the insulin dose prior to the activity by 50%. For patients using an insulin pump, the basal rate can be similarly adjusted as an alternative.

If the exercise session is more than ~ 2 hours after the meal, additional carbohydrate should be consumed just before the exercise, rather than making changes in insulin dosing, except for patients using an insulin pump, where adjusting the basal rate is again an option. If the exercise is to promote weight loss it is reasonable to “hold back” some food at the meal, take less insulin for that meal, and consume the “held back” food just before the exercise without additional insulin.

Because of the persistence of the glucose lowering effect of exercise, insulin may need to be cut another 10 – 20% at the 1 – 2 meals after the exercise, as may basal insulin for 6 – 12 hours.

C. The site of insulin injection before exercise:

The abdomen is the preferred injection site, rather than the legs or arms, because exercise can alter the rate of insulin absorption from the active limbs, particularly if the insulin was injected near muscle or accidentally into muscle.

D. The amount of supplemental carbohydrate:

If the exercise is to be prolonged or late after an insulin injection and insulin therefore cannot be adjusted, some form of carbohydrate should be ingested before, during and after exercise. In general this should match the amount of energy being expended. Note that to just ingest carbohydrate before the exercise will raise the blood glucose too much; smaller amounts ingested throughout exercise are better. The amount of carbohydrate needed is based on the duration and intensity of exercise. Table 1 gives examples of amounts of carbohydrate to try as a starting point. Remember, if you are trying to lose weight, eat less the meal before and adjust that insulin.

Table 1. Listed in this table is the total amount of carbohydrate that should be consumed at intervals before, during, and after one hour of physical activity. If the activity continues past 1 hour, simply continue with the supplemental carbohydrate every 30 minutes.

Exercise Intensity Caloric Expenditure Amount of Carbohydrate Amounts of Carbohydrate to be Consumed During Exericise
Low - Moderate 4 -8 kcal/min
240 - 480 kcal/hour
60 to 120 gm 15 - 30 gm before exercise
15 - 30 gm after 30 mins. of exercise
15 - 30 gm after 60 mins. of exercise
15 - 30 gm 15 - 30 mins. after exercise

 

Moderate - High 8 - 12 kcal/min
480 - 720 kcal/hour
120 to 180 gm 30 - 45 gm before exercise
30 - 45 gm after 30 mins. of exercise
30 - 45 gm after 60 mins. of exercise
30 - 45 gm 15 - 30 mins. after exercise
Intense

12 - 16 kcal/min
720 - 960 kcal/hour
 

180 to 240 gm 45 - 60 gm before exercise
45 - 60 gm after 30 mins. of exercise
45 - 60 gm after 60 mins. of exercise
45 - 60 gm 15 - 30 mins. after exercise

Table 2 lists some actual drinks and foods that you may want to try. In general we recommend fast acting carbohydrates early (such as milk, Gatorade or a similar sport drink, or regular soda) and more slowly acting carbohydrates at the end of the exercise.

Food or Drink Calories (kcals)/Carbohydrates (CHO)
Regular soda (4 oz.) 50 kcals/15 g CHO (varies - see label)
Gatorade (4 oz.) 103 kcals/26 g CHO
Whole milk (4 oz.) 75 kcals/6 g CHO
Skim milk (4 oz.) 45 kcals/6 g CHO
5 Saltines 60 kcals/11 g CHO
1 Graham cracker square 30 kcals/5 g CHO
1 oz. Pretzels 110 kcals/22 g CHO
Fruit juice (4 oz.) 60 kcals/15 g CHO (varies - see label)

As already discussed, because of the persistence of the glucose lowering effect of exercise, insulin may need to be cut another 10 – 20 percent at the 1 – 2 meals after the exercise, as may basal insulin for 6 – 12 hours. An alternative to cutting insulin is to consume additional carbohydrate late after exercise. You can try another 10 – 20 percent of the supplemental carbohydrate consumed during exercise at 4 – 8 hours later.

After determining the caloric expenditure, the pre-exercise blood glucose concentration must be considered. If pre-exercise blood glucose is higher than desired, but still below 250 mg/dl, then less carbohydrate should be ingested. A general guideline is that for every 50 mg/dl above the desired blood glucose level, pre-exercise carbohydrate can be reduced by 15 g.

E. Learn from experience

It is critical that people with diabetes learn about their individual responses to exercise, by trial and error. Each of the guidelines presented in this brief review will have to be modified based upon unique individual responses. During initial exercise sessions, until repeated success determines the correct mix, it is a very good idea to keep a record of blood glucose responses, insulin dose and timing, and carbohydrate intake.

Remember:

  • Always carry fast-acting glucose with you, such as the carbohydrate drinks discussed
  • Try to exercise with a friend who knows you have special considerations
  • Always carry identification that states you have diabetes
  • If you exercise alone, carry a mobile phone if possible
  • A note of caution is that persons with loss of pain sensation in the feet due to neuropathy should choose an activity that does not increase the risk of damage to the feet

 

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