Insulin requirements and exercise

Exercise has been shown to bring many benefits to those who have type 1 diabetes and rely on insulin to control blood glucose levels.

These include

• lower cardiovascular risk, and better cardiovascular function
  • better control of blood sugars, blood pressure, and weight
• improved insulin sensitivity, lower insulin requirements

All of these lead to improvements in the health outcomes for patients with type 1 diabetes ultimately leading to a longer lifespan (1, 2)

• in type 1 diabetes, there is a reduction in insulin requirements both during exercise and 24 hours afterwards. Reasons include:
  • there is a more rapid absorption of insulin from an exercising rather than non-exercising limb
  • there is an increase in insulin-dependent glucose uptake as a result of exercise
    
    
• type 1 diabetics need to carefully monitor glucose when commencing on an exercise regimen; also they should be advised to reduce insulin doses before and after exercising (especially if using long-acting insulin)

Advice for patients (3,4,5,6,7,8)

• diabetic patients, especially those using insulin, need to know how their glycaemic control can be affected by different forms of physical activity
  • patients' confidence can be increased by appropriate advice on checking blood glucose concentrations before and after activity, and, with respect to insulin treated diabetics, carrying rapid- and intermediate-acting carbohydrate whenever they plan to exercise
    
    
• for type 2 diabetics taking oral medication for diabetes
  • a reduction in the dose may be required if prolonged exercise is planned
    
    
• for type 1 diabetics
  • guidelines recommend that, because of the risk of precipitating ketoacidosis, exercise should be avoided if the fasting glucose concentration before physical activity is more than 13 mmol/L and ketosis is present (6)
  • the guidelines also advise caution if glucose concentration is more than 17 mmol/L and no ketosis is present
  • if blood sugar level is above 13 mmols/l but less than 17 mmols/l, limit exercise activity to moderate intensity (walking, light biking), rather than a high intensity exercise (running, weight lifting, tennis) (6)
  • amount of exercise
    • 150 minutes of moderate aerobic activity, or 75 mins strenuous activity
    • 1 hour of resistance exercise
  • it is important for those exercising who have diabetes that they monitor their blood sugar levels frequently especially before and after exercise (5,6)
  • if required they may need to monitor their levels during exercise as well, especially if doing prolonged exercise (5,6)
  • it should be noted that a reduction in Insulin requirement will last for 12-15 hours following any exercise and Insulin should be adjusted accordingly (3,4,5,8)
  • if blood sugar is <5.5mmol/l take a carbohydrate snack prior to exercise
  • additional carbohydrates (30-60g/hour) should be consumed every 30-60 minutes of exercise to avoid hypoglycaemia
  • when exercising participants should make others aware of their condition and also be aware themselves of how they feel when they may be getting a low blood sugar
  • consider wearing an alert bracelet
  • consult early if non healing foot ulcers or particular concern
  • consult doctor before doing extreme sports including scuba diving, climbing, surfing, parachuting
    
    

Resources for GP's/ Patients

• may include local diabetes clinics, or speaking to other people they know who have diabetes
• diabetes UK has a good section on exercise and diabetes http://www.diabetes.co.uk/exercise-for-diabetics.html from Diabetes UK
• http://www.ausport.gov.au/sportscoachmag/nutrition2/the_highs_and_lows_of_diabetes_and_exercise

Contributors:

• Dr Alethea Beck. General Practitioner, Scottish Borders
• Dr Andrew Murray. General Practitioner, Sports and Exercise Medicine registrar, Scotland

Reference:

• 1. Brukner P & Khan K. Clinical Sports Medicine, 3rd Edition. McGraw Hill, London, 2006
• 2. Zisser H et al, 2011. Exercise and Diabetes. International Journal of Clinical Practice, Feb 65:suppl 170: 71-75
• 3. Prescriber (2001), 12 (14), 43-50.
• 4. Drug and Therapeutics Bulletin 2005; 43(10):73-77
• 5. Australian Institution of Sport Fact Sheets: Diabetes and Sports Nutrition, (http://www.ausport.gov.au/ais/nutrition/factsheets/special_diets2/diabetes_and_sports_nutrition)
• 6. Exercise for Diabetics, diabetes.co.uk, 2011, www.diabetes.co.uk
• 7. Diabetes UK, 2011, http://www.diabetes.org.uk
• 8. American Diabetes Association, http://www.diabetes.org/