Manage Diabetes with Exercise

When you have diabetes you may often be encouraged to “do some exercise”. So, why is exercise particularly recommended for you? Well, there is no doubt that regular physical exercise can improve your health and well being and helps control your weight but don’t forget it can be fun too!

As diabetes is largely a condition where you manage your day-to-day treatment yourself, you need to understand what happens to the body during exercise. This will help you to optimize your blood glucose control, improve your performance, avoid hypoglycemia and ultimately tailor a plan to suit your lifestyle.

What happens to the body during exercise?

Exercise is a challenge to the body, which therefore needs plenty of oxygen and fuel (such as glucose or fat) to meet its demands. Everyone knows that their heart rate and breathing both increase when they exercise – this provides more oxygen to their muscles. In same way that a fire needs oxygen to burn, the body ideally needs plenty of oxygen to help it burn fuel to make energy.

The fuel the muscles need comes from:

• Glucose stores in the muscle (glycogen);
• From fat stores; and
• From glucose made by the liver.

People without diabetes can keep their blood glucose levels in a narrow range during exercise by balancing the glucose their muscles use against the glucose their body produces. This process is controlled by the hormones their body releases in response to exercise: adrenaline, glucagon and growth hormone. These hormones are balanced by very small amounts of insulin, which stops the blood glucose levels rising above normal levels.

Aerobic and anaerobic exercise

Exercise can be split into two types:

• Aerobic exercise: During aerobic exercise plenty of oxygen is available to the muscles, allowing them to burn glucose and fats completely to make energy. Typically, endurance sports are aerobic.
• Anaerobic exercise: Anaerobic exercise starts when there is not enough oxygen in the muscles. As a result, fats cannot be used for energy and glucose is not burnt completely, leaving behind a waste product called lactate.

Sprint sports are anaerobic - often the sprinters breathe only once, or not at all. By the end of the race their muscles are very short of oxygen, are therefore working anaerobically and lactate is being formed.

When lactate levels are too high, you will have to stop exercising, as you will feel very short of breath, perhaps even nauseous, and your heart rate will increase (generally above 140 beats per minute).

Training can increase both your capacity for aerobic exercise and your tolerance of the lactate produced during anaerobic exercise.

Exercise and diabetes – what happens?

When you have diabetes your body is unable to control blood glucose levels and, during exercise, your blood glucose can rise or fall, depending upon the type of exercise you take:

• Anaerobic exercise: during short periods of anaerobic exercise, or exercise with short bursts of activity, your glucose may rise
• Aerobic exercise: in contrast, glucose levels generally fall with prolonged aerobic exercise.

Hypoglycemia after exercise can also be a problem.

Which exercise is best for me?

While any exercise is beneficial, you should choose an activity that best meets your goals and is safe for you to do. Prolonged aerobic exercise at low intensity is the best for weight control. Any ‘antigravity’ or ‘weight-bearing’ exercise such as running, or using a treadmill with an incline in a gym for 40 minutes at a time will help burn fat. Cycling is also good, but swimming is less effective as your body weight is supported by water. Be careful if you have diabetic foot problems. Running and treadmill work are not recommended for you. Also, if you have heart, eye or blood pressure problems, advice should be sought prior to starting your exercise program.

Planning for exercise

It makes sense to plan for exercise in advance rather than to take extra glucose later to deal with hypoglycemia. Here are a few pointers:

• Before starting any new exercise program discuss it with your healthcare provider. In particular discuss with them how to adjust your pre-exercise insulin or diabetes tablets.
• You need to think about the timing, duration and intensity of the exercise so you can plan your diabetes treatment, food intake and blood glucose testing.
• Test your blood glucose regularly during and following exercise and immediately take steps to correct falling blood glucose.
• Glucose (30-60 grams per hour) in the form of a drink or as tablets can help protect you against hypoglycemia.

Having diabetes should not be a barrier to exercise; instead remember that exercise can be both beneficial and enjoyable. Thought and planning is needed to optimize your blood glucose control, and blood glucose needs to be tested before and following exercise. Your food intake may need to be altered to reduce the risk of hypoglycemia.

Important Notice: Information provided is for general background purposes and is not intended as a substitute for medical diagnosis or treatment by a trained professional. You should always consult your physician about any health care questions you may have, especially before trying a new medication, diet, fitness program, or approach to health care issues.

DOC11720-Rev-A 04/08