Diabetes and Exercise

Indications

Recommendations about exercise regimen come from the American Heart Association, the American Diabetes Association, and the American College of Sports Medicine standards of medical care in diabetes (2013).[1][2]

Type 1 and type 2 patients with diabetes are encouraged to do 30 to 60 minutes of moderate-intensity aerobic activity. Patients suffering from diabetes should also be encouraged to perform resistance training at least twice per week. Patients with moderate to severe proliferative retinopathy have contraindications for resistance training. Otherwise, for physically fit patients, a shorter duration of more vigorous aerobic exercise is recommended.

Moderate-intensity aerobic activity: Perform 30 to 60 minutes of moderate-intensity aerobic activity on most days of the week. Begin with 10 minutes of stretching and warm-up, follow that with 15 to 20 minutes of aerobic exercise of person’s choice such as walking, running, swimming, dancing, cycling, or rowing to name few. Maintain regularity in exercise regimen at least three to five times per week. Continue to perform exercise at the same time in relation of meals and insulin injections. Gradual increment in duration and intensity as tolerated by the patient should be planned. Goal is to perform 150 minutes of moderate-intensity aerobic exercise per week.[3][4]

Resistance training: Exercise with free weights or weight machines. In the absence of contraindications listed above, patients should perform resistance training at least twice per week. Patients should involve the larger group of muscles for exercise training, such as core, upper and lower body. Proliferative retinopathy may cause retinal bleeding due to Valsalva maneuvers with a possibility of marked increase in blood pressure precipitating intraocular bleeding in such patients.[5]

Vigorous aerobic exercise: Patients with diabetes who are generally fit, exercising regularly and have higher aerobic capacity may perform 75 minutes per week of more vigorous aerobic exercise. The preferable regimen is jogging 9.6 km per hour. An alternative regimen can be low-volume, high-intensity training, during which patients exercise more vigorously for a shorter amount of time, such as cycling at 85% to 90% percent of individual maximal heart rate for 60 seconds, followed by 60 seconds of rest, with a total of 10 repetitions. The long-term health effects of low-volume, high-intensity training is unknown. Again, as with moderate excise regimen, a gradual increment in duration and intensity as tolerated by the patient should be planned.[5]

Contraindications

Relative contraindications for exercise regimen include proliferative retinopathy that may cause retinal bleeding due to Valsalva maneuvers with a possibility of a marked increase in blood pressure precipitating intraocular bleeding in such patients. Diabetic neuropathy should avoid traumatic weight-bearing, as it leads to pressure ulcers.[1]

Clinical Significance

Short-Term Effects of Exercise[6][7][8]

Pathophysiology

Type 2 Diabetes: Exercise leads to an increase in insulin sensitivity. Patients on oral hypoglycemic have decreased blood glucose concentration after exercise. Studies have suggested that patients who were fasting, no change in blood glucose concentrations noted; whereas, blood concentrations decreased in patients who exercised after eating.

Type 1 Diabetes

• Patients with well-controlled diabetes on insulin regimen: Higher serum insulin concertation is noted during exercise due to increased temperature and blood flow leading to increased absorption from subcutaneous depots. Exogenous insulin can’t be shut off. Hence, these patients have a drop in blood glucose levels much larger than in normal individuals.
• Patients with diabetes and poor metabolic control: Exercise causes a paradoxical elevation in blood glucose concentrations

Long-Term Effects of Exercise[9][10]

Pathophysiology

Patients have impaired exercise capacity due to generally increased body mass index and advanced age. Reduced skeletal muscle oxidative capacity due to mitochondrial dysfunction has been responsible for impaired exercise capacity. Patients are insulin resistant due to many defects in glucose metabolism.

• Decreased number and function of both insulin receptors and glucose transporters
• Decreased activity of some intracellular enzymes
• Low maximal oxygen uptake during exercise

An exercise program leads to increased activity of mitochondrial enzymes, increased insulin sensitivity, and muscle capillary recruitment. Adding resistance training to aerobic exercise provides an additional benefit of increased insulin sensitivity.

Blood Glucose Management During Exercise[11][12][13]

General principles for patients with diabetes mellitus for exercise regimens:

• Maintain a high level of fluid intake before, during, and after exercise
• Maintaining blood sugar logs before, during, and after exercise
• If blood glucose is less than 100 mg/dL, it is recommended to ingest food, such as glucose tablets, juice. About 15 to 30 grams of quickly absorbed carbohydrate is recommended to be ingested 15 to 30 minutes before exercise. Extra ingestion of food may be warranted during exercise based on blood glucose testing during the exercise.  Immediately after excise slowly absorbed carbohydrates such as dried fruit, granola bars or trail mix are recommended as patients are at risk of late hypoglycemia.
• Vigorous exercise is to be avoided in the presence of substantial hyperglycemia greater than 250 mg/dl.
• Hypoglycemia is not common in patients with type 2 diabetes not treated with insulin or oral hypoglycemics. Ingestion of extra carbohydrates is not required.
• Use insulin about 60 to 90 minutes before exercise to prevent increased insulin absorption along with injecting in a site other than muscle to be exercised. For example, inject into arms when cycling exercise and into the abdomen when the exercise involves both the arms and legs.

Enhancing Healthcare Team Outcomes

Long-Term Compliance and an Interprofessional Approach[14]

Maintenance of the exercise program in patients with type 2 diabetes is an important goal because it is associated with long-term cardiovascular benefits and reduced mortality. Primary care physicians and nursing professional diabetes educators caring for patients play an important role in educating these patients of the importance of exercise regimen as a therapeutic option for the disease management. There have been studies which suggested simple behavioral counseling by clinicians and nurse educators during routine clinic visits gave encouraging results for increasing compliance, although long-term follow-up is needed.

Exercise regimens are difficult to maintain for more than 3 months due to intense nature of the programs requiring extra visits for special classes. In a 10-year study of 255 patients with diabetes enrolled in a diabetes education program emphasizing exercise, the rate of compliance fell from 80% for 6 weeks to less than 50% for 3 months. The compliance rate further dropped to less than 20% at 1 year. A coordinated interprofessional approach with educators working with clinicians will help to maximize compliance. (Level V)