Types of diabetes are recognized based on their etiological origin: type 1, type 2, gestational (diagnosed during pregnancy) and other specific origins (genetic and drug-induced defects); however, most patients have type 2 (90% of cases), followed by type 1 (5 to 10% of all cases).
With regard to physical exercise, according to the Guidelines of the Brazilian Society of Diabetes Mellitus 2017-2018 (2017), in association with diet, moderate aerobic activity is recommended, which would be rapid walking, taking 150 minutes weekly, divided into three sections, each of which should last at least 10 minutes and at most 75 minutes.
Type 1 DM is most frequently caused by the autoimmune destruction of pancreatic insulin-producing b cells, although some cases have an idiopathic origin (it appeared spontaneously or of obscure or unknown cause).
The main characteristics of individuals with type 1 DM are absolute insulin deficiency and high propensity to ketoacidosis (Severe complication of diabetes that occurs when the body produces excess blood acids (ketones)).
Type 2 diabetes is caused by insulin-resistant skeletal muscle, adipose tissue, and liver combined with a defect in insulin secretion. A common feature of type 2 diabetes is excess body fat with fat distribution in the upper body portion (abdominal or central obesity). Central obesity and insulin resistance often progress to pre-diabetes.
According to the Guidelines of the Brazilian Diabetes Society 2017 – 2018 (2017), Diabetes and its complications are the main causes of early mortality in most countries; approximately 5 million people aged between 20 and 79 years died from diabetes in 2015, equivalent to one death every 6 seconds.
Exercise-associated care in individuals with diabetes: hypo and hyperglycemia
In individuals with T1D in insulin deprivation for 12 to 48 hours or in underdose use (e.g., dose omission) with hyperglycemia and ketosis, physical exercise can worsen hyperglycemia, worsening ketosis and dehydration. Traditional recommendations suggested the suspension of physical exercise in case of glucose above 250 mg/dL in the presence of ketosis or in case of glucose above 300 mg/dL, even in the absence of ketosis.
In individuals with T2DM, however, if they are well insulinized or have good insulin reserves, especially if in the post-prandial period, mild to moderate exercise helps to decrease blood glucose.
Patients with T2DM do not need to postpone physical exercise because of hyperglycemia, as long as they feel well, prepared and fit for the exercise they propose; the tendency is that glucose levels fall with activity, which can be done safely, and attention should be paid to hydration in the presence of hyperglycemia.
In patients with T1D, on the other hand, increased blood glucose after high-intensity exercise can be avoided by using a small additional dose of ultra-fast insulin in the middle of the activity or after the end of the exercise, taking care to note that this exercise will later increase insulin sensitivity and may favor late hypoglycemia.
Physical exercise is one of the most frequent precipitating factors of hypoglycemia, which occurs due to excess circulating insulin during exercise, either by increased absorption of insulin injected into the subcutaneous tissue (induced by physical activity),
either by the loss of the endogenous capacity to reduce the circulating levels of insulin during exercise, impairing the hepatic release of glucose, which predisposes the individual to hypoglycemia between 20 and 60 minutes after the beginning of exercise.
Another important factor is the loss of the counterregulatory mechanism by previous exercise sessions or by a recent hypoglycemic episode. Thus, athletes with T1DM who presented hypoglycemia in the days preceding a competition are at greater risk of hypoglycemia associated with exercise.
Exercise also improves insulin sensitivity in the peripheral muscles, an effect that can be maintained for several hours to days after exercise, so that some athletes with T1D may present a condition known as late hypoglycemia related to exercise, which can happen when the athlete is sleeping, determining, in these cases, the need for more frequent monitoring or extra snacks.
As for exercise modality, an alternative to minimize the risk of hypoglycemia is to intermediate “explosion” activities (such as short shots, for example) or anticipate resistance exercise by performing it before aerobic training, in order to minimize the hypoglycemic effect of the latter.
General care and recommendations on physical activity in diabetes mellitus
Each exercise session should include periods of 5 to 10 minutes of warm-up with low intensity aerobic exercise. After warming up, it is necessary to stretch for another 5 to 10 minutes. At the end of the exercise, the cooling period should also be 5 to 10 minutes, bringing the heart rate back to the resting level.
Foot care in aerobic physical activity is essential for individuals with diabetes: adequate tennis shoes, eventually with the use of special insoles (if indicated) and appropriate socks (without internal stitching), the way to keep the feet comfortable and dry, especially in those with diabetic neuropathy.
Individuals should always be reminded of the importance of examining their feet before and after the exercises, paying attention to the appearance of blisters. An identification bracelet should be worn by an athlete with diabetes, especially one who is using insulin or at risk of hypoglycemia.
For children and adolescents, aerobic physical activity of 60 minutes per day (recreational) and vigorous activities three times a week are recommended. In adults, it is indicated moderate aerobic exercise with duration of 150 minutes per week, intense aerobic exercise of 75 minutes per week or the combination of the two intensities, besides exercises of muscular strengthening at least twice a week.
According to the ACSM (2014), the benefits of regular exercise for individuals with type 2 DM and pre-diabetes include improved glucose intolerance, increased sensitivity to insulin and decreased HbA1C.
In individuals with type 1 DM and those with type 2 DM using insulin, regular exercise reduces insulin requirements. Some of the important benefits caused by exercise in individuals with type 1 or type 2 DM or pre-diabetes include improved risk factors for CVD (lipid profiles, blood pressure [BP], body weight and functional capacity) and well-being.
Participation in regular exercise may also prevent or at least delay the transition to type 2 diabetes in individuals with pre-diabetes who have a high risk of developing diabetes.
For those with type 2 diabetes and pre-diabetes, exercise increases sensitivity to insulin by increasing cellular uptake of glucose from the blood, facilitating improvement in glucose control.
For those with type 1 diabetes, increased insulin sensitivity has little impact on pancreatic function, but often reduces the need for exogenous insulin.
Often, healthy weight loss and adequate body weight maintenance are more important issues for those with type 2 diabetes and pre-diabetes; however, excess weight and body fat may also be present in individuals with type 1 diabetes and the exercise program may be useful in this context.
According to Lima e Silva (2002), a physical exercise program with aerobic activities and localized muscular resistance, 4 times a week with 60-minute sections for Type 2 Diabetes Mellitus, results in the benefits of improved fasting glucose and HbA1, decreased glycerides and increased HDL-C.
According to Marins and Guttierres (2008), ACSM recommends the PFF twice a week, 8-10 exercises involving large muscle groups, of at least a series of 10-15 repetitions close to fatigue.
The ADA recommends that light loads and a high number of repetitions be used to increase strength in all patients with DM2. TF with intensity between 60 and 100% of 1 MRI requires functional and metabolic structural changes in the muscles, and higher intensities cause greater adaptations.
PFF has been shown to improve the glucose elimination rate, increase the glycogen stock capacity, increase GLUT 4 receptors in the muscle, increase insulin sensitivity and normalize glucose tolerance.