The Complete Guide to Exercise Intervention for Diabetes: Pathological Analysis, Blood Glucose Monitoring, and Practical Guide to Exercise Prescription

Diabetes mellitus is a clinical syndrome characterized by a series of metabolic disorders caused by an absolute or relative deficiency of insulin in the body, or by insulin resistance in tissue cells. It is closely related to genetics. The World Health Organization classifies diabetes into: type 1 diabetes, type 2 diabetes, gestational diabetes, and other types of diabetes. All types of diabetes result in the pancreas's beta cells failing to produce sufficient insulin or in insulin receptor dysfunction, leading to hyperglycemia. Type 1 diabetes is generally caused by autoimmune disorders that impair the function of insulin-producing beta cells; type 2 diabetes is caused by insulin resistance in tissue cells, beta cell dysfunction, or other factors.

The typical symptoms of diabetes, commonly referred to as the "three highs and one low"-excessive thirst, excessive hunger, excessive urination, and weight loss-primarily occur in patients with type 1 diabetes. The distinction between type 1 and type 2 diabetes is actually unrelated to body shape; both obese and underweight patients can have type 2 diabetes. Obesity is one of the most important contributing factors to type 2 diabetes. Obese patients have fewer insulin receptors and reduced sensitivity to insulin, resulting in insulin resistance. Although they can secrete insulin, the secreted insulin is insufficient to lower blood sugar. Weight gain coupled with lack of exercise creates a vicious cycle, leading to obesity, which in turn causes excessive food intake and elevated blood glucose levels.

The human body contains polysaccharides, disaccharides, and monosaccharides; blood glucose refers only to glucose in the blood. In normal individuals, blood glucose is in dynamic equilibrium, with fasting blood glucose levels typically between 3.3 and 6.1 mmol/L. Blood glucose originates from food digestion and absorption, the breakdown of glycogen stored in the liver, and gluconeogenesis from fats and proteins. After ingestion, starchy foods are broken down into glucose by digestive enzymes, which is absorbed into the bloodstream, increasing blood glucose concentration. This stimulates pancreatic β-cells to secrete insulin, which promotes glucose transport into cells, entering liver cells to synthesize liver glycogen and entering muscle cells to synthesize muscle glycogen.

There are various methods for testing diabetes, but blood glucose is the only reliable diagnostic indicator. Generally speaking, postprandial blood glucose is more sensitive than fasting blood glucose, and blood glucose 2 hours after a meal is even more important than fasting blood glucose. Fasting blood glucose mainly reflects the blood glucose level in a basal state before dietary intake, reflecting the patient's own insulin secretion capacity. Measuring postprandial blood glucose can help understand the control of diabetes and easily identify when hyperglycemia occurs. If both fasting and postprandial blood glucose are high, it is essential to lower the fasting blood glucose first, because once the fasting blood glucose decreases, the postprandial blood glucose will follow suit.

Glycated hemoglobin (HbA1c) is a component of hemoglobin formed by the slow, non-enzymatic binding of hemoglobin and glucose. In 2002, the American Diabetes Association adopted it as the gold standard for monitoring blood glucose control in diabetes. The formation of HbA1c is irreversible, and its synthesis rate is positively correlated with blood glucose concentration. Because the average lifespan of red blood cells is 120 days, its level represents the average blood glucose level over those 120 days. Blood glucose tests only represent immediate blood glucose levels, indicating the patient's physical condition at the time of testing, while HbA1c reflects the long-term degree of disease control.

The therapeutic effects of exercise intervention on type 2 diabetes are widely recognized. Endurance exercise can increase the utilization of glucose by muscle tissue and increase calorie expenditure. Exercise promotes the direct uptake of blood glucose by skeletal muscle, thus lowering blood sugar. Exercise can also enhance insulin sensitivity; in obese patients, the binding rate of insulin to receptors increases during exercise, reducing insulin resistance and thereby improving glucose metabolism. In addition, the enhanced respiratory and circulatory functions and increased oxygen supply during exercise play a certain role in preventing the occurrence of diabetic cardiopulmonary complications.

Obese patients with diabetes must undergo a medical history review, physical examination, and medical tests before starting exercise for weight loss. The appropriate exercise intensity and type should be determined for each individual, such as walking, brisk walking, flat-ground cycling, Tai Chi, or aerobics. Excessive strength training is not recommended. Obese patients with diabetes should engage in at least 30 minutes of moderate-intensity aerobic exercise daily. Exercise is generally best scheduled 90 minutes after a meal, as this is when blood sugar levels are highest. Avoid exercising immediately after insulin injection to prevent hypoglycemia. Carry candy or sugary drinks with you during exercise to prevent hypoglycemia.

Treatment of diabetes requires a combination of medication, diet, and exercise, with diet being a fundamental measure. Diabetic patients should limit their fat intake to 25%–30% or even lower of their total daily energy intake. Protein intake should be close to the normal range, approximately 1 gram per kilogram of body weight per day. Increasing dietary fiber intake is encouraged, as it helps control postprandial blood sugar spikes. Meals should be reasonably scheduled; to reduce the burden on the pancreas, at least three meals a day are recommended. Restrictions on staple foods should be relaxed; it is suggested that carbohydrates should account for 50%–60% of total energy intake.

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