Glucose requirements to maintain euglycaemia during and following moderate intensity afternoon exercise in adolescents with type 1 diabetes mellitus: an insight to the risk of exercise-associated hypoglycaemia.

Sarah McMahon

    Research output: ThesisDoctoral Thesis

    227 Downloads (Pure)

    Abstract

    Exercise has a wide range of benefits for patients with type 1 diabetes, including improvements in body composition, cardiovascular risk profile and glycaemic control. Unfortunately, exercise also increases the risk of hypoglycaemia in children with type 1 diabetes, both at the time of exercise and for many hours afterwards. The availability of clear, evidence-based guidelines regarding appropriate adjustments in carbohydrate intake or insulin doses may help to prevent this exercise associated hypoglycaemia. However, current guidelines regarding exercise in children with type 1 diabetes rely heavily on adult literature or the consensus of experts. Therefore, further studies are needed in young people with diabetes to document the metabolic responses during and following exercise. In particular, the mechanisms underlying hypoglycaemia occurring many hours after exercise require further exploration. In addition, as children often exercise in the afternoon, studies performed at this time of the day are more likely to be transferrable to a real life situation. For this reason, we studied adolescents with type 1 diabetes to investigate physiological responses to exercise, focusing on afternoon activity and employing a novel variation of the euglycaemic insulin clamp technique. The core experiments involved studying diabetic adolescents on two occasions in a counterbalanced, paired design during and after afternoon exercise. Insulin was infused at a constant rate based on the subjects' usual daily insulin dose and glucose was infused to maintain euglycaemia. At 1600 hrs subjects either exercised at a moderate intensity (95% of their lactate threshold) for 45 minutes on a cycle ergometer (exercise study), or sat on the ergometer without exercising (rest study). Using this experimental design, it was found that glucose infusion rates (GIR) to maintain euglycaemia were elevated during and shortly following exercise and again from 7-11 hours after exercise compared with the rest study. Counterregulatory hormone levels were similar between the exercise and rest studies except for peaks in noradrenaline, cortisol and growth hormone levels at the end of exercise. Glucagon and adrenaline levels did not increase with exercise. The observed biphasic increase in glucose requirements paralleled the observed clinical risk of hypoglycaemia immediately during exercise and the delayed risk of hypoglycaemia which often occurs overnight.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2009

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