Importance of Exercise

Physical exercise is a fundamental pillar, along with diet, diabetes education and drugs, in the treatment of diabetes mellitus.


Before beginning physical activity, the person with diabetes mellitus should undergo a detailed medical evaluation.

The young person with good metabolic control of his diabetes can practice most physical activities. The middle-aged and the elderly with diabetes, should do systematic physical activity, but always with medical advice.

It is important during exercise to pay attention to maintaining good hydration. Dehydration can damage blood sugar levels and heart function. It is advisable to drink fluids before starting physical activity. And during physical activity, fluids should be given to compensate for losses through sweating.


When a person with type 1 diabetes has little insulin in their circulation due to inadequate insulin treatment and/or an exaggerated release of counterinsulin hormones during physical activity, the level of blood sugar and ketone bodies may increase, which can lead to diabetic ketosis or ketoacidosis.

Conversely, if insulin levels are high, due to external insulin administration, it may attenuate or impede the increased mobilization of glucose and other substrates stimulated by physical activity and, therefore, a picture of hypoglycaemia may occur.


In general, hypoglycemia during physical activity is usually a minor problem in these people. Generally, in people with type 2 diabetes, physical activity improves insulin sensitivity and contributes to lowering the elevated blood glucose level to a normal range. Different studies have shown that physical exercise is effective in the prevention and treatment of type 2 diabetes.


The benefits of aerobic and endurance exercise, according to several researchers, are these:

Improves insulin sensitivity.

  • Improvement in hypercoagulability states.
  • Greater use of glucose by the muscle, which helps prevent hyperglycemia.
  • Improvement of the abnormal reaction of catecholamines to stress.
  • Overall improvement of heart function and blood pressure.
  • Increased energy expenditure and fat loss, which helps to control body weight and prevent obesity.
  • Contribution to improve levels of “good” or HDL cholesterol and to decrease levels of triglycerides and total cholesterol.
  • Decrease in the incidence of some types of cancer.
  • Reduction of osteoporosis.
  • Improvement of the sensation of well-being.
  • Improved body elasticity.
  • Prevents depression, anxiety and stress.
  • Long-term reduction of the risk of diabetes complications.


In people who use insulin, physical activity can cause hypoglycemia if the dose used or carbohydrate intake is not adequate. In these cases the ingestion of rapidly absorbed carbohydrates should be recommended when preexercise blood glucose levels are < 100 mg/dL. Hypoglycaemia is more rare in diabetics who are not treated with insulin.

In people with type 2 diabetes affected by proliferative diabetic retinopathy, physical exercise with sudden movements of the head or weight-lifting exercises may cause bleeding into the retina or vitreous, endangering vision.

People with diabetes are vulnerable to plantar ulceration due to bone deformities and can affect the ankle joint and its mobility. For this type of person, exercises that are accompanied by: high plantar pressures or secondary forces for the weakened musculature should be limited.

In people who do not have sensitivity in the feet, is contraindicated long walks, jumping and stair exercises. In these cases it is recommended: swimming, bicycling, seated exercise and arm exercises, among others.

In people with diabetes, high-risk exercises are not recommended, where the patient cannot receive immediate help (mountaineering, hang-gliding and diving, among others). Nor should those with poor diabetes control exercise, because exercise worsens the metabolic state.

Indeed, high-risk patients should be allowed to start with low-intensity exercise for short periods of time, and then increase the intensity and duration progressively. Specialist doctors will contraindicate exercises that are predisposed to cause injury.


Hypoglycaemia is the main limitation in blood glucose control for type 1 and type 2 insulin-treated diabetics. This can happen during physical activity, as soon as it is finished, or several hours after its completion, but it can be avoided. In order to do this, the patient must know the metabolic and hormonal responses produced by physical exercise in the body.

Those who use insulin or products that stimulate the endogenous secretion of insulin, should check their capillary blood glucose before, at the end and several hours after the end of an exercise session, at least until they know their usual glycaemic response to the activity.

For those who have a tendency to hypoglycaemia during or after exercise, several tactics can be applied: reducing doses of insulin or products that stimulate insulin secretion, consuming some extra portions of rapidly absorbed carbohydrates before or during prolonged exercise, or combining both.
Several factors determine the risk of hypoglycemia.

The lowering of the blood glucose level is further accelerated if the exercise is done at the time of the high action of the injected insulin. There are data that indicate that the rate of decrease in blood glucose is higher if the injection is made in the exercising limb. For example, for runners it is recommended that insulin be injected into the abdomen before physical exercise, rather than into the thigh.

The later the exercise is done after the injection, the less likely it is that this effect will pass. In addition, some patients may experience lower blood glucose levels for up to 30 hours after the end of exercise, due to the continued glucose consumption of the exercise muscle cells by replenishing their intracellular glucose stores.

Measures to take in the prevention of hypoglycaemia in diabetics who are treated with insulin

  • Decrease the dose of regular insulin or ultrafast acting analogues from 10% to 40% before exercise, depending on the duration and intensity of the session.
  • Inject regular insulin or analog insulin with ultrarapid action in the abdominal subcutaneous area.
  • Check blood glucose before starting the exercise session.
  • Exercise 3 to 4 hours after regular insulin injection or 2 hours after if insulin analogues injection is ultrafast acting.
  • Take 20 to 60 g of simple carbohydrates before starting, if your blood glucose is < 120 % mg (6.6 mmol/L).
  • Delay the exercise session before starting if your blood glucose is < 80 % mg (4, 4 mmol/L).
  • Take 20 to 60 g of simple carbohydrates every 30 min, if exercise is of moderate intensity or high intensity.
  • Check blood glucose 30 minutes after exercise.
  • Decrease the dose of insulin that is usually administered after exercise, if you use regular insulin or an analog of ultrarapid action between 10 and 30% before the next meal.
    Many nutritionists’ guidelines recommend an amount of about 30-60 grams of carbohydrates/hour during exercise.

The American College of Sports Medicine in 2009 made recommendations on nutrition and sports performance in which it recommended:

For exercises longer than 60 minutes the additional intake of 0.7g/kg per hour. For example, a 70 kg person would need 49 g of carbohydrates per hour of exercise to increase endurance performance.

Special circumstances:

Exercise in the diabetic elderly

It can be said with certainty that the progressive loss in physical conditions of strength and muscle mass that accompany the aging process can be prevented by regular physical exercise.

When a person begins to age there is a reduction in insulin sensitivity, largely due to a lack of physical activity.

The population at risk for type 2 diabetes mellitus is more susceptible to little physical activity. Some studies have confirmed in older people a good response to physical training, reflected by improved metabolic control. In these people, adaptation to physical exercise programmes was very similar to that observed in younger people.

These activities can positively favor the prevention of chronic diseases, such as diabetes mellitus, high blood pressure and metabolic syndrome, among others.