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Type 1 diabetes: no barrier to athletic prowess; A simple formula can help a would-be athlete get started on a moderate exercise program.

QUEBEC CITY -- Gary Hall Jr. has type 1 diabetes. He also has 10 Olympic medals in swimming and is one of the fastest swimmers in the United States.

Hall's trips to the podium are thanks to his own sweat and muscle power, but he also gives credit to his endocrinologist, who didn't let Hall's diabetes get the better of him. In fact, Hall powered to four Olympic medals 1 year after his 1999 diagnosis.

It is that kind of attitude that physicians should cultivate when counseling athletes who have diabetes, said Bruce Perkins, M.D., an endocrinologist at the University of Toronto. "I truly believe that someone with diabetes should be able to lead as adventurous, as creative, and as challenging a life as in a parallel life without diabetes," he said.

"As health care professionals, we need to decide whether we are going to be permissive or inhibitive in our approach toward athletes with diabetes," Dr. Perkins said at the annual meeting of the Canadian Diabetes Association and the Canadian Society of Endocrinology and Metabolism.

"If someone with diabetes aspires to be an athlete, there should be a way that health care professionals can help them to meet this goal," he told this newspaper.

A wealth of evidence shows the benefits of exercise in the prevention of type 2 diabetes, as well as in the management of the condition once it has developed. Yet there is very little in the literature showing the benefits of exercise in patients with type 1 diabetes, Dr. Perkins said.

Exercise can send blood sugars either up or down, depending on the intensity and type of activity (aerobic or anaerobic) and when it is done (before or after a meal). As a result, the adjustment of insulin doses can be complex and challenging, he said.

In response to a diagnosis of type 1 diabetes, many physicians and athletes react by backing away from a challenging exercise regimen. But this is not necessary. A simple formula can get a would-be athlete started or keep an established athlete on a moderate exercise program that can be fine-tuned later as exercise intensity increases.

Wearing an insulin pump is not essential, but it can make insulin adjustments easier--especially for athletes involved in endurance sports, Dr. Perkins said.

"It is a very, very valuable tool, but I wouldn't say that exercise is the only reason that someone should be on a pump. For some people, the pump could be dangerous if they are not checking blood sugars frequently enough and if they are not comfortable with the mechanics," he said.

An important distinction to make is whether an athlete is involved in aerobic or anaerobic exercise, because this can make a fundamental difference in glucose metabolism, Dr. Perkins said.

Anaerobic exercise, such as sprinting, involves the release of counterregulatory hormones (cortisol and epinephrine) that can sharply increase glucose release from the liver. This can lead to hyperglycemia, dehydration, and impaired athletic performance if not enough insulin is administered at the right time. Dr. Perkins advises such athletes to make sure they have good blood sugar levels at the time of their activity and to monitor themselves carefully afterward.

But athletes with type 1 diabetes are more likely to be involved in aerobic sports--short-term activities, such as exercise classes, or perhaps endurance workouts, such as long-distance running. In aerobic activity, there is a less marked release of counterregulatory hormones, and the main risk is hypoglycemia as the muscles use up glucose.

"If these patients start their exercise with high levels of insulin, they need to be eating during the exercise session, or else their blood sugar can run low very easily," Dr. Perkins said, adding that because of this, he generally advises patients to do their long workouts before a meal, with only their basal insulin on board.

To reduce the risk of hypoglycemia, he advises patients to start out following a simple rule: In preparation for a workout, they must either increase their carbohydrate intake, or decrease their insulin dose. The rule can be adjusted later to fit individual needs.

For patients who choose extra carbohydrates, a simple formula is to eat 15-30 g every 30-60 minutes during exercise. When the patient is ready to fine-tune this, a more sophisticated formula can be used: Most activities require about 1 g of carbohydrate per kilogram of body weight per hour of exercise.

Patients who choose to adjust their insulin dose have a choice of adjusting their basal (long-acting) insulin, or their pre-meal bolus (short-acting). If adjusting the pre-meal dose, a general rule is to reduce the dose by 25%-50%, depending on the intensity and duration of exercise. If the basal dose is being adjusted, Dr. Perkins advises a 25%-50% reduction starting 90 minutes before the start of the activity and ending 90 minutes after the end.

"The most important thing is getting someone started and then adjusting the formula to fit their needs," he said, adding that patients must be committed to checking their blood sugars every 30 minutes during their exercise session until they have fine-tuned their insulin requirements.


Montreal Bureau
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Title Annotation:Endocrinology
Author:Johnson, Kate
Publication:Internal Medicine News
Geographic Code:1USA
Date:Jan 1, 2005
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