Exercise is extremely important in managing diabetes because of its effects on lowering blood glucose and reducing cardiovascular risk factors. Exercise lowers the blood glucose level by increasing the uptake of glucose by body muscles and by improving insulin utilization. It also improves circulation and muscle tone. Resis-tance (strength) training, such as weight lifting, can increase lean muscle mass, thereby increasing the resting metabolic rate. These effects are useful in diabetes in relation to losing weight, easing stress, and maintaining a feeling of well-being. Exercise also alters blood lipid levels, increasing levels of high-density lipoproteins and decreasing total cholesterol and triglyceride levels. This is es-pecially important to the person with diabetes because of the in-creased risk of cardiovascular disease (Creviston & Quinn, 2001). General guidelines for exercise in diabetes are presented in Chart 41-5.
Patients who have blood glucose levels exceeding 250 mg/dL (14 mmol/L) and who have ketones in their urine should not begin exercising until the urine tests negative for ketones and the blood glucose level is closer to normal. Exercising with elevated blood glu-cose levels increases the secretion of glucagon, growth hormone, and catecholamines. The liver then releases more glucose, and the result is an increase in the blood glucose level (ADA, Phys-ical Activity/Exercise and Diabetes Mellitus, 2003).
The physiologic decrease in circulating insulin that normally occurs with exercise cannot occur in patients treated with insulin. Initially, the patient who requires insulin should be taught to eat a 15-g carbohydrate snack (a fruit exchange) or a snack of com-plex carbohydrate with a protein before engaging in moderate ex-ercise, to prevent unexpected hypoglycemia. The exact amount of food needed varies from person to person and should be de-termined by blood glucose monitoring. Some patients find that they do not require a pre-exercise snack if they exercise within 1 to 2 hours after a meal. Other patients may require extra food re-gardless of when they exercise. If extra food is required, it need not be deducted from the regular meal plan.Another potential problem for patients who take insulin is hypoglycemia that occurs many hours after exercise. To avoid postexercise hypoglycemia, especially after strenuous or prolonged exercise, the patient may need to eat a snack at the end of the ex-ercise session and at bedtime and monitor the blood glucose level more frequently.
In addition, it may be necessary to have the pa-tient reduce the dosage of insulin that peaks at the time of exer-cise. Patients who are capable, knowledgeable, and responsible can learn to adjust their own insulin doses. Others need specific instructions on what to do when they exercise.
Patients participating in extended periods of exercise should test their blood glucose levels before, during, and after the exercise pe-riod, and they should snack on carbohydrates as needed to main-tain blood glucose levels (ADA, Physical Activity/Exercise and Diabetes Mellitus, 2003). Other participants or observers should be aware that the person exercising has diabetes, and they should know what assistance to give if severe hypoglycemia occurs.
In obese people with type 2 diabetes, exercise in addition to dietary management both improves glucose metabolism and en-hances loss of body fat. Exercise coupled with weight loss im-proves insulin sensitivity and may decrease the need for insulin or oral agents. Eventually, the patient’s glucose tolerance may return to normal. The patient with type 2 diabetes who is not taking in-sulin or an oral agent may not need extra food before exercise.
People with diabetes should exercise at the same time (preferably when blood glucose levels are at their peak) and in the same amount each day. Regular daily exercise, rather than sporadic exercise, should be encouraged. Exercise recommendations must be altered as necessary for patients with diabetic complications such as retinopathy, autonomic neuropathy, sensorimotor neuropathy, and cardiovascular disease (ADA, Physical Activity/Exercise and Dia-betes Mellitus, 2003). Increased blood pressure associated with ex-ercise may aggravate diabetic retinopathy and increase the risk of a hemorrhage into the vitreous or retina. Patients with ischemic heart disease risk triggering angina or a myocardial infarction, which may be silent. Avoiding trauma to the lower extremities is especially important in the patient with numbness related to neuropathy.
In general, a slow, gradual increase in the exercise period is en-couraged. For many patients, walking is a safe and beneficial form of exercise that requires no special equipment (except for proper shoes) and can be performed anywhere. People with diabetes should discuss an exercise program with their physician and un-dergo a careful medical evaluation with appropriate diagnostic studies before beginning an exercise program (ADA, Physical Activity/Exercise and Diabetes Mellitus, 2003; Creviston & Quinn, 2001; Flood & Constance, 2002).
For patients who are older than 30 years and who have two or more risk factors for heart disease, an exercise stress test is rec-ommended. Risk factors for heart disease include hypertension, obesity, high cholesterol levels, abnormal resting electrocardio-gram, sedentary lifestyle, smoking, male gender, and a family his-tory of heart disease.
Physical activity that is consistent and realistic is beneficial to the elderly person with diabetes. Physical fitness in the elderly popu-lation with diabetes may lead to less chronic vascular disease and an improved quality of life (ADA, Physical Activity/Exercise and Diabetes Mellitus, 2003). Advantages of exercise in this popula-tion include a decrease in hyperglycemia, a general sense of well-being, and the use of ingested calories, resulting in weight reduction. Because there is an increased incidence of cardiovascu-lar problems in the elderly, a pattern of gradual, consistent exer-cise should be planned that does not exceed the patient’s physical capacity. Physical impairment from other chronic diseases must also be considered. In some cases a physical therapy evaluation may be warranted with the goal of determining exercises specific to the patient’s needs and abilities. Tools such as the “Armchair Fitness” video may be helpful. For more information about age-related changes that affect diabetes management see Chart 41-6.
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