Benefits of Exercise

Regardless of the type of diabetes, regular physical activity is important for your patients' overall health and wellness (ADA, 2023). 

Physical Activity Recommendations: A = best evidence for improved outcome, B = good supportive evidence for improved outcome, C = some evidence/concensus or conflicting evidence for improved outcome

• Children and adolescents with type 1 or type 2 diabetes or pre-diabetes should engage in 60 min/day or more of moderate- or vigorous-intensity aerobic activity, with vigorous muscle-strengthening and bone-strengthening activities at least 3 days/week.
• Most adults with type 1 C and type 2 B diabetes should engage in 150 min or more of moderate-to-vigorous intensity aerobic activity per week, spread over at least 3 days/week, with no more than 2 consecutive days without activity. Shorter durations (minimum 75 min/week) of vigorous-intensity or interval training may be sufficient for younger and more physically fit individuals.
• Adults with type 1C and type 2 B diabetes should engage in 2–3 sessions/week of resistance exercise on nonconsecutive days.
• All adults, and particularly those with type 2 B diabetes, should decrease the amount of time spent in daily sedentary behavior. Prolonged sitting should be interrupted every 30 min for blood glucose benefits B, particularly in adults with type 2 diabetes C. 
• Flexibility training and balance training are recommended 2–3 times/week for older adults with diabetes. Yoga and tai chi may be included based on individual preferences to increase flexibility, muscular strength, and balance C.

Exercise has been shown to improve blood glucose control, reduce cardiovascular risk factors, contribute to weight loss, and improve well-being.

Warning: routine physical activity is an important part of the diabetic care plan. Any change in physical activity will effect glycemic control. The attending physician and registered dietician must be notified of alterations in activity so that appropriate adjustment to diet and medication can be made to compensate for changed activity level. Changes in physical activity will also require increased vigilance and glucose testing until the effects of the new routine are known.

Special (diabetic) considerations for physical activity:

• Drink plenty of fluids while being physically active to prevent dehydration (harmful loss of water in the body).
• Make sure to check your blood sugar before being physically active, especially if you take insulin.
  • If it’s below 100 mg/dL, you may need to eat a small snack containing 15-30 grams of carbohydrates, such as 2 tablespoons of raisins or ½ cup of fruit juice or regular soda (not diet), or glucose tablets so your blood sugar doesn’t fall too low while being physically active. Low blood sugar (hypoglycemia) can be very serious.
  • If it’s above 240 mg/dL, your blood sugar may be too high (hyperglycemia) to be active safely. Test your urine for ketones – substances made when your body breaks down fat for energy. The presence of ketones indicates that your body doesn’t have enough insulin to control your blood sugar. If you are physically active when you have high ketone levels, you risk ketoacidosis – a serious diabetes complication that needs immediate treatment.
• When you’re physically active, wear cotton socks and athletic shoes that fit well and are comfortable.
• After your activity, check to see how it has affected your blood glucose level.
• After being physically active, check your feet for sores, blisters, irritation, cuts, or other injuries. Call your health care provider if an injury doesn’t begin to heal after 2 days.

Source: Get Active! https://www.cdc.gov/diabetes/managing/active.html

While physical activity is recommended for nearly everyone, the benefits of exercise for people with diabetes are even greater than for non-diabetics. Aerobic exercise provides the safest and most benefits for people with diabetes to achieve blood glucose control and to improve cardiovascular status.

The current American Diabetes Association recommendations are:

• "People with diabetes should be advised to perform at least 150 min/week of moderate-intensity aerobic physical activity (50-70% of maximum heart rate)".
• "In the absence of contraindications, people with type 2 diabetes should be encouraged to perform resistance training three times per week"

Moderate to high levels of aerobic activity are associated with substantially lower cardiovascular and overall mortality risks in both type 1 and type 2 diabetes.

Aerobic exercise promotes cardio-pulmonary distribution of oxygen throughout the body. Aerobic exercise involves repetitive contraction of major muscle groups at a rate and intensity that does not result in rapid oxygen depletion. Optimum aerobic exercise occurs between 70-80% of maximun effort. Continuous moderate intensity swimming, cycling, walking or jogging are examples of aerobic exercise.

Anaerobic exercise is high intensity, short duration exercise that exceeds the body's ability to supply oxygen.  Anaerobic exercise results in oxygen deficit and lactic acid production.  Anaerobic exercise occurs between 80-90% of maximum effort. Examples of anaerobic exercise include: resistance training, heavy weight-lifting, any type of sprint, isometrics, etc. Anaerobic exercise does not confer the same health benefits as an aerobic program. In addition, anaerobic exercise and certain types and intensity levels of aerobic exercise may produce excessive rises in blood pressure, cardiac workload, and pressure within the eye (intraocular pressure). These reactions can be potential problems in persons with diabetes who have eye disease or cardiovascular disease.

Exercise was first recommended as a therapy for lowering blood glucose levels in the 20th century. Regular exercise is now a primary component of diabetes management. Much of the morbidity and mortality associated with diabetes are due to cardiovascular disease. Research studies have consistently demonstrated that regular exercise and physical fitness are associated with decreased cardiovascular disease in the population at large and a decrease in the incidence of type 2 diabetes. 

Although regular exercise is beneficial for everyone, here are some specific benefits of exercise for people with diabetes:

• Improved glucose control
• Reduced risk of progression from pre-diabetes to type 2 diabetes
• Decreased risk of diabetes associated coronary artery disease, including a reduction in triglycerides, and low-density lipoproteins (LDLs), and an increase in high-density lipoproteins (HDLs)
• Increased sensitivity to insulin is greatest with a combined program of aerobic and resistance training
• Reduced hyperinsulinemia (excessive insulin secretion), a potential risk factor for atherosclerosis
• Increased fibrinolysis (breakdown of clots in the circulatory system)
• Reduced A1c in type 2
  

In patients with type 1, it’s very important to balance insulin doses with food and activity blood sugar response to exercise will vary depending on:

• blood sugar level at the start
  
• the intensity of the activity
  
• the length of time the patient is active
  
• Monitor blood sugars before and after exercising.

Evidence supporting exercise

• Richter, (2021), reports that exercise increases muscle uptake of glucose by as much as 100 times the rate of resting muscle.
• Riddell et al., (2023) conducted a study involving 497 adults with type 1 diabetes. The glucose response during and after individual exercise events is highly variable, aerobic exercise produces a greater decline in glycemia than high-intensity interval exercise, followed by resistance exercise. Even in adults with well-controlled type 1 diabetes, days with structured exercise sessions contributed to clinically meaningful improvement in glucose time in range but may have slightly increased time below range.
• Soo, et al. (2023),  identify skeletal muscle as the predominant site for insulin-mediated glucose uptake, and that regular exercise training is a significant factor for glycaemic control. Importantly, they found that exercise enhanced glucose transport remains intact in individuals with T2DM, but there is wide variability in response among individuals. Factors that may contribute to this variability include:
  • duration of T2DM
  • dietary intake,
  • exercise-related factors such as the volume, type and intensity of exercise
  • the magnitude of glycogen depletion during exercise
  • exercise induced hypoxia
• Verboven et al. ( 2019 ) in a systematic literature review showed that, in T2DM patients, improvements were observed in diastolic function, but not consistently in systolic function, after endurance (and combined resistance) exercise training. Different exercise intervention modalities and exercise types seemed equally effective in improving cardiac structure and function.
• Exercise/Physical Activity in Individuals with Type 2 Diabetes: A Consensus Statement from the American College of Sports Medicine identifies multiple forms of physical activities that have proven benefits including: improved insulin sensitivity, postprandial hyperglycemia, and reduced CVD risk.
  • Types of structured exercise
    • Aerobic exercise training - Rhythmic, continuous physical activity, that increases oxygen demand and improve cardiovascular endurance.
    • Resistance exercise training - High intensity weight lifting or resistance training may increase lean muscle mass and decrease A1C.
    • Combined exercise training - Combined aerobic and resistance exercise training may be superior to either mode alone.
    • High-Intensity Interval Exercise (HIIE) - HIIE training is a regimen that involves aerobic training done between 65-90% VO2peak or 75-95% heart rate peak (HRpeak) for 10 sec to 4 min with 12 sec to 5 min of active or passive recovery. Close monitoring is required.
  • Consensus Statements and Recommendations
    • High-intensity resistance exercise has greater benefits than low-to-moderate-intensity resistance training in terms of glucose management and insulin levels.
    • Physical activity throughout the day, breaking up sitting time, can also help reduce postprandial glucose and insulin levels, particularly in individuals with insulin resistance and a higher body mass index.
    • Weight loss ≥ 5% through diet and physical activity is necessary for beneficial effects on A1C, blood lipids, and blood pressure.
    • Moderate to high volumes of exercise are needed for reducing visceral fat in individuals with type 2 diabetes.
    • 20-30 minutes of physical activity is recommended for pregnant women with and without diabetes.
    • Individuals with type 2 diabetes who execise while using insulin or insulin secretagogues are advised to supplement with carbohydrate to prevent hypoglycemia
    • Participating in an exercise program before bariatric surgery may improve surgical outcomes, and after surgery does confer health benefits.

References

American Diabetes Association (2023). Standards of Care in Diabetes—2023 Abridged for Primary Care Providers. Clin Diabetes; 41. Accessed 8/18/2023 from https://diabetesjournals.org/clinical/article/41/1/4/148029/Standards-of-Care-in-Diabetes-2023-Abridged-for

Kanaley, J. A., Colberg, S. R., Corcoran, M. H., Malin, S. K., Rodriguez, N. R., Crespo, C. J., Kirwan, J. P., & Zierath, J. R. (2022). Exercise/Physical Activity in Individuals with Type 2 Diabetes: A Consensus Statement from the American College of Sports Medicine. Medicine and science in sports and exercise, 54(2), 353–368. https://doi.org/10.1249/MSS.0000000000002800

Richter E. A. (2021). Is GLUT4 translocation the answer to exercise-stimulated muscle glucose uptake?. American journal of physiology. Endocrinology and metabolism, 320(2), E240–E243. https://doi.org/10.1152/ajpendo.00503.2020

Soo, J., Raman, A., Lawler, N. G., Goods, P. S. R., Deldicque, L., Girard, O., & Fairchild, T. J. (2023). The role of exercise and hypoxia on glucose transport and regulation. European journal of applied physiology, 123(6), 1147–1165. https://doi.org/10.1007/s00421-023-05135-1

Verboven, M., Van Ryckeghem, L., Belkhouribchia, J., Dendale, P., Eijnde, B. O., Hansen, D., & Bito, V. (2019). Effect of Exercise Intervention on Cardiac Function in Type 2 Diabetes Mellitus: A Systematic Review. Sports medicine (Auckland, N.Z.), 49(2), 255–268. https://doi.org/10.1007/s40279-018-1003-4