Open-loop intravenous insulin waveforms for postprandial exercise in type I diabetes

Guidelines for premeal insulin dose reduction for postprandial exercise of different intensities and durations in type 1 diabetic subjects treated intensively with a basal-bolus insulin regimen (ultralente-lispro)

OBJECTIVE

To evaluate and validate appropriate premeal insulin dose reductions for postprandial exercises of different intensities and durations to minimize the risk of exercise-induced hypoglycemia in type 1 diabetic subjects.

RESEARCH DESIGN AND METHODS

Eight male type 1 diabetic patients on a basal-bolus insulin regimen of ultralente (UL) as basal insulin and lispro (LP) as premeal insulin were tested in a randomized, crossover fashion during postprandial exercise at 25% VO2max for 60 min, 50% VO2max for 30 and 60 min, and 75% VOmax for 30 min starting 90 min after a standardized mixed breakfast (600 kcal, 75 g carbohydrates). Each subject served as his own control and was rested after a full dose of insulin LP (LP 100%) and/or 50% (LP 50%) and/or 25% (LP 25%) of the current dose.

RESULTS

At all intensities, the full premeal insulin dose was associated with an increased risk of hypoglycemia. At 25% VO2max for 60 min, a 50% reduction in the premeal insulin dose resulted in plasma glucose of -0.62 mmol/l compared with baseline at the end of exercise. At 50% VO2max for 30 and 60 min, 50 and 75% reductions of the premeal insulin dose were associated with plasma glucose of -0.39 and +0.49 mmol/l, respectively, at the end of the exercise. At 75% VO2max, a 75% reduction of the premeal insulin dose was required to achieve appropriate postexercise plasma glucose (+0.71 mmol/l). Such reductions in the premeal insulin dose resulted in a 75% decrease in the incidence of exercise-induced hypoglycemia. CONCLUSIONS In well-controlled type 1 diabetic subjects on intensive insulin therapy with the basal-bolus (UL-LP) insulin regimen, risk of hypoglycemia can be minimized during postprandial exercises of different intensities and different durations by appropriate reduction of premeal insulin LP.

Nutrition and exercise in individuals with diabetes

Individuals with type 1 (insulin-dependent diabetes mellitus [IDDM]) and type 2 (non-insulin-dependent diabetes mellitus [NIDDM]) diabetes should be encouraged to exercise. Although there is an absence of consistent evidence that adaptations to routine exercise improve glucose control in type 1 diabetes, there is evidence that shows improved glucose control in individuals with type 2 diabetes. Although both groups benefit from exercise, the merit and suitability of routine exercise is measured by the extent to which the advantageous adaptive effects of regular exercise surpass the risks of a sole bout of exercise. In addition, when considering acute versus routine exercise, special considerations must be given to children with diabetes and older adults at risk for insulin resistance. Finally, a greater research focus is needed on engaging in competitive and recreational sports so that children and adults with diabetes may participate safely in activities such as baseball, swimming, basketball, soccer, and hockey.

Managing Activity in Patients Who Have Diabetes

In brief Control of both type I and type II diabetes involves the appropriate balance of exercise, diet, and medication. Regular, long-term exercise has many benefits for people with diabetes. Physicians can educate patients about ways to regulate and monitor blood glucose before, during, and after a workout or competition. Physicians also need to discuss the warning signs of hypoglycemia, hyperglycemia, ketoacidosis, and dehydration and how to prevent the conditions. In addition, patients who have type I diabetes need to know the effects of exercise on insulin requirements. Nutrition needs will vary for each patient, type of activity, and other factors, but food intake can be readily adjusted in conjunction with blood glucose monitoring.

Exercise prescription for individuals with metabolic disorders. Practical considerations

Regular exercise has been recognised as an important component in the management of patients with diabetes mellitus. In addition to acutely lowering blood glucose, exercise training improves glucose tolerance and peripheral insulin sensitivity, contributes to weight loss and reduces several risk factors for cardiovascular disease. When proper precautions are taken to prevent hypoglycaemia, individuals with diabetes can enjoy the same benefits from exercise as nondiabetic healthy individuals. As a guideline, moderate intensity, aerobic endurance activities should be performed for 20 to 40 minutes at least 3 times a week. Blood glucose should be monitored, and insulin dose and carbohydrate intake adjusted based on the blood glucose response to the type and duration of exercise. This review will summarise current understanding of the therapeutic role of exercise in the treatment of diabetes and will present guidelines for prescribing exercise in diabetic patients.

Exercise in type 1 (insulin-dependent) diabetic patients treated with continuous subcutaneous insulin infusion. Prevention of exercise induced hypoglycaemia

The study was performed to investigate the effects of mild to moderate exercise on blood glucose levels, metabolite concentrations and responses of counterregulatory hormones in tightly controlled Type 1 (insulin-dependent) diabetic patients treated by continuous subcutaneous insulin infusion, and to quantify the measures necessary to prevent acute and late exercise-induced hypoglycaemia. Seven male patients started a 60 min exercise period 90 min after an insulin bolus and a standard breakfast; they were monitored during a post-exercise resting period of 5 h 30 min. Different basal and premeal insulin infusion rates were applied. (Near)normoglycaemia prevailed throughout the study during the control protocol when the subjects did not exercise and received their usual insulin dose. When they exercised without changing the insulin dose, four patients were forced to stop due to hypoglycaemia. This effect of exercise could be attenuated but not completely avoided if the basal infusion rate of insulin was discontinued during the exercise period. The pronounced increase in catecholamine and growth hormone concentrations during exercise were not sufficient to prevent hypoglycaemic reactions. Hypoglycaemia during exercise could only be prevented when the premeal insulin bolus was reduced by 50% in addition to the discontinuation of the basal insulin infusion during exercise. In order to reduce late hypoglycaemic reactions after exercise the best measure proved to be a reduction of the basal insulin infusion rate by 25% during post-exercise hours. Administration of only 50% of the basal insulin infusion rate during this time was associated with blood glucose levels being raised up to 8 mmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes, insulin and exercise

The metabolic and hormonal adaptations to single exercise sessions and to exercise training in normal man and in patients with insulin-dependent as well as non-insulin-dependent diabetes mellitus are reviewed. In insulin-dependent (type I) diabetes good metabolic control is best obtained by a regular pattern of life which will lead to a fairly constant demand for insulin from day to day. Exercise is by nature a perturbation that makes treatment of diabetes difficult: Muscle contractions per se tend to decrease the plasma glucose concentration whereas the exercise-induced response of the so-called counter-regulatory hormones tend to increase plasma glucose by increasing hepatic glucose production and adipose tissue lipolysis. If the pre-exercise plasma insulin level is high, hypoglycaemia may develop during exercise whereas hyperglycaemia and ketosis may develop if pre-exercise plasma insulin levels are low. Physical activity is often difficult to carry out on a precise schedule and the exercise-induced changes in demand for insulin and calories vary according to the intensity and duration of exercise, time of day, and differ within and between individuals. Thus, physical training can not be recommended as a means of improving metabolic control in insulin-dependent diabetes. However, our present knowledge and technology allows the well-informed and cooperative patient to exercise and even to reach the elite level. To achieve this, pre-exercise metabolic control should be optimal and knowledge of the patient's reaction to exercise is desirable, which necessitates frequent self-monitoring of plasma glucose. It may often be necessary to diminish the insulin dose before exercise, and/or to ingest additional carbohydrate during or after exercise. In non-insulin-dependent (type II) diabetes, exercise is associated with less risk of metabolic derangement, and in genetically disposed individuals physical training may prevent development of overt diabetes possibly by diminishing the strain on the pancreatic beta cell. The latter, however, is only achieved if exercise is not accompanied by increased caloric intake. Whether physical training in diabetes can reduce cardiovascular morbidity and mortality is at present unknown, but training has in diabetic patients been shown to lessen some risk factors for development of arteriosclerosis. However, training of diabetics (especially in the less well-regulated patient) may not lessen coronary risk factors to the same extent as in healthy subjects.

Diabetes and exercise

The abnormal metabolic responses to exercise in insulin-dependent diabetes are in great part related to abnormal circulating plasma insulin concentrations. Exercising during relative insulin deprivation results in an increase in glycemia and ketosis. Exercise during insulin excess results in inhibition of hepatic glucose production and accelerated muscle glucose utilization and results in hypoglycemia. These responses can be significantly improved when insulin is administered more appropriately, as is the case with insulin infusion pumps. Self blood glucose monitoring before, during, and after exercise can provide important information that can be used to optimize the metabolic response to exercise in individual patients. A better understanding of the metabolic response to exercise in patients with diabetes will serve as the basis for developing specific recommendations to enable these individuals to have the freedom to take part in all forms of exercise with minimal restriction. However, the demonstration that exercise will have a long-term beneficial effect on the metabolic control of diabetes or prevent the development of the complications of diabetes remains to be established.