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Exercise is currently recommended for indivduals with type 1 diabetes since it is associated with physiological and psychological benefits (American Diabetes Association Position Statement, 2004; American College of Sports Medicine, 2010). However participation in exercise can increase the risk of experiencing hypoglyceamia, both during exercise and recovery (Rabasa-Lhoret et al., 2001). Through discussions with practitioners that work with individuals that have type 1 diabetes, the development of clear evidence -based guidelines regarding adjustments in insulin doses and carbohydrate intake may help prevent the risk of exercise induced hypoglyceamia. Specifically, there are limited evidence based guidelines for participation in intermittent high intensity exercise (IHE), which represents activity patterns of team and field based sports. Consequently, the aim of this thesis is to investigate the effects of a structured intervention for insulin and carbohydrate adjustment on blood glucose responses during and after IHE that replicates team and field based sports in individuals with type 1 diabetes. Seven well-controlled participants with type 1 diabetes were tested on three separate occasions and interstitial glucose concentration was measured up to breakfast the following day on each occasion using a Continuous Glucose Monitor (CGM). The first phase of this study compared a 30% post-exercise fast-acting analogue insulin reduction on the blood glucose responses to an afternoon bout of IHE (40 minutes of cycles of walking for 5 minutes at 40% O V 2 max, jogging for 3 minutes at 70% O V 2 max and sprinting for 5 seconds at 125% O V 2 max) vs. continuous moderate intensity exercise (40 minutes at 50% O V 2 max). Results showed there was no significant difference between the CGM readings for moderate or IHE (p= 0.59) at any point during the 40 minute exercise protocols and up to breakfast the following day. There was a significant change in interstitial blood glucose concentration over time regardless of exercise condition (p< 0.001). Regardless of exercise condition both moderate and IHE is characterised by the risk of Late Onset Post-Exercise Hypoglycaemia (LOPEH). In addition there appears to be a problem of hyperglycaemia, particularly two-four hours after the meal and insulin reduction. The second phase of the study compared the blood glucose responses to a 30% vs. a 50% post-exercise fast-acting analogue insulin reduction after a bout of afternoon IHE in individuals with type 1 diabetes. There was no significant difference in interstitial blood glucose responses as measured by CGM between the two insulin reductions and 50% insulin reduction is no better for the prevention of LOPEH than the 30% reduction after IHE (p= 0.06). Blood glucose responses were similar for the same IHE on two separate occasions and there was a significant decrease in in interstitial blood glucose concentration as measured by CGM from 0-40 minutes of exercise (p= 0.002). As observed in phase 1, the problem of hyperglycaemia was also evident. In conclusion, there are two main high-risk periods for the development of hypoglycaemia associated with IHE. The first is immediately after exercise and the second later on during the night. In addition hyperglycaemia seems to be a problem for up to four hours following the evening meal after exercise. It is important to make patients aware of this, in order to prevent the long term complications associated with such. Regardless, individuals vary in their responses to exercise and individual strategies to combat hypoglycaemia may be required. A number of limitations are acknowledged within this study, however is they were eradicated, future research of this kind could have implications for the development of guidelines for the management of blood glucose concentration during and after IHE.
Lorraine Steele (Thu,) studied this question.