Physical training in the treatment of type 1 diabetes

The role of physical activity has been emphasized in improving well-being and self-esteem in type 1 diabetic patients also. Although data specifically addressing type 1 diabetic patients are not available, exercise should have the same cardiovascular benefits in type 1 diabetic as in type 2 diabetic patients, provided the insulin treatment regimen and diet can be accurately adjusted to maintain normal glucose homeostasis during exercise.

Effect of physical training on glucose control and insulin requirements

Most studies have found no difference in glycemic control between type 1 diabetic patients who are physically active compared to those who are inactive [64,72,73], and no improvement in glycemic control by physical training [74-77]. On the other hand, physical training does improve and even normalize insulin sensitivity in type 1 diabetic patients [77] (Fig. 4.4.5), and this is associated with slight (5%) decreases in insulin requirements [75,77].

Effect of physical training on vascular function and cardiovascular risk markers in type 1 diabetic patients

Endothelial dysfunction, defined as an inability of the endothelium to release normal amounts of nitric oxide, characterizes some [78-81] but perhaps not all [82-86] patients with type 1 diabetes. The impact of physical activity on endothelial dysfunction has been sparsely studied. In one cross-sectional analysis, endothelial function, measured from perfusion changes in the skin microcirculation during iontophoresis with acetylcholine, was similar between physically active and inactive patients with type 1 diabetes [64]. Exercise does seem to have favorable effects on serum lipids and lipoproteins also in type 1 diabetic patients. In controlled studies, physical training has also been shown to lower total [76] and LDL [74] cholesterol and triglyceride [74] concentrations and to increase HDL cholesterol [74], HDL cholesterol/ total cholesterol [74,76,77] and apoA-I [76] concentrations. In all of the controlled studies, these changes occurred independent of glycemic control and body weight and composition [74,76,77]. In uncontrolled or cross-sectional analyses, physical activity is associated with increases in HDL2 cholesterol and decreases in serum triglycerides and LDL cholesterol [87,88].

Poorly controlled patients with type 1 diabetes are characterized by changes in markers indicative of increased oxidative stress such as increased levels of plasma thiobarbituric acid reactive substance (TBARS), reduced total radical trapping capacity [89], increased levels of oxidized LDL [89] and antibodies against oxidative LDL [90]. During acute exercise (40 min at 60% Vo ), markers of oxidative stress such as

TBARS and blood oxidized glutathione concentrations increase by 50% [91]. The significance of this with regards to long-term effects of training on cardiovascular function is unknown.

Little information is available on effects of different types of training on markers of metabolic control or cardiovascular risk. Aerobic circuit exercise training has been suggested to induce similar changes in body composition and lipids in type 1 diabetic patients as in normal subjects and type 2 diabetic patients but this study was uncontrolled [92] (Table 4.4.2).

Diet and insulin treatment during exercise

In normal subjects, the serum insulin concentration decreases during prolonged exercise in response to a slight decrease in glucose concentrations and protects against hypoglycemia [73]. In patients with type 1 diabetes, the serum free insulin concentration is determined by the amount of insulin injected, its rate of absorption, insulin antibodies and insulin clearance. During exercise, the serum free insulin concentration is frequently higher than in normal subjects. This can be due to overinsulinization or injection of insulin before exercise, inability of glucose to regulate insulin concentrations or acceleration of insulin absorption by exercise, if insulin has been injected in a region which is actively exercising [93]. Overinsulinization increases the risk of hypoglycemia. On the other hand, if the insulin concentration is subnormal, this will allow the exercise-induced increase in counterregu-latory hormones to stimulate hepatic glucose production excessively, which leads to hyperglycemia. Excessive counterregulatory responses in poorly controlled patients may further exaggerate hyperglycemia

In a well-controlled type 1 diabetic patient, it is usually recommended to increase carbohydrate intake by 20-40 g/h before or during exercise to prevent hypo-glycemia. If hypoglycemia occurs despite this, the insulin dose should be reduced. To avoid changes in insulin absorption by exercise, insulin should be injected in a region which is inactive, and it is not recommended to exercise immediately after injection of regular insulin or a rapid-acting insulin analog [95]. Use of short-acting analogs has been shown to increase the risk of hypoglycemia if exercise is performed shortly (40 min) after a meal but reduce it by approximately 50% if exercise is performed 3 h after a meal

In addition to the precautions necessary to minimize the occurrence of exercise-induced hypo- or hyperglycemia, the presence of complications should also be considered. This applies to type 1 [73] as well as type 2 [96] diabetic patients. Patients with proliferative retinopathy, poorly controlled hypertension or evidence of cardiovascular disease should avoid strenuous activities such as heavy weight-lifting and sprints. Individuals with autonomic neuropathy may experience postural hypotension after exercise. Heart rate responses may also be abnormal, which is why ratings of perceived exhaustion rather than heart rate should guide intensity of exercise. Non-weight-bearing activities should be preferred by patients with foot problems and peripheral neuropathy to avoid injuries and additional damage to feet [73,96].

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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