Basic Facts

1In the absence of a meal, your blood glucose level is a balance between glucose being made by the body (mostly by the liver) and glucose being used up by muscle as an energy source.

 

In people without diabetes the islet cells within the pancreas are able to increase or decrease insulin production to prevent swings in glucose above or below the normal range. For people using insulin this does not occur and once insulin is injected or infused from a pump high levels are produced. These high levels of insulin prevent the liver from being able to make extra glucose for exercise – increasing the risk of a hypo.

 

The opposite also occurs with some forms of exercise whereby the body’s response to exercise can be to produce chemicals (hormones) that have the opposite effect to insulin and turn on the liver to make more glucose. These so-called counter-regulatory hormones also reduce the ability of muscles to use glucose as a fuel. The net result is a high level of glucose in the bloodstream which, as well as being unpleasant and causing dehydration, can impair an athlete’s performance.

 

It is very difficult to establish a good diabetes exercise regime with both pump therapy and injections of insulin if the day to day diabetes control isn’t optimal. It may be sensible to perform some basal assessments of insulin prior to starting an intensive exercise program. Your diabetes healthcare team can help with this.

 

The risk of hypoglycaemia depends on

  1. Type of exercise – aerobic activity is more likely to cause hypoglycaemia than resistance training
  2. Intensity of exercise – high intensity aerobic exercise (e.g. running) is more likely to cause hypoglycaemia whereas high intensity resistance training (e.g. weights) can cause hyperglycaemia
  3. Duration of exercise – the longer you exercise the more likely the risk of hypoglycaemia. Usually blood glucose starts to drop after 30 minutes of aerobic exercise.