The effects of reducing insulin versus eating carbohydrates on glycaemic control and performance with aerobic exercise in type 1 diabetes

25 Male Participants (in groups of 5 participants at a time) will be performing a walking exercise for 45 mins on a standardized treadmill at a 1% gradient. The brisk walk will be determined by participants trying to maintain the speed of 7.24 kilometers per hour throughout the entire 45 min. Following the aerobic exercise, participants will perform a six-minute walk test which is a validated measure of predicted VO2 max and will serve as a performance test. This will be followed by a 7 days washout period and then the same group of participants will be repeating the above process for the crossover treatment. Ninety minutes before the exercise all participants on continuous subcutaneous insulin infusion (CSII; known as insulin pump therapy) will start a 50% temporary basal rate reduction as per guidelines. Sixty minutes before the exercise, all participants will eat a carbohydrate predominant mixed meal individualized to contain 0.66 g of carbohydrate/kg of body and 3.375 kcal/kg of body weight, meeting the requirements of both energy expenditure and exercise carbs guidelines Participants in the reduced insulin group will administer 50% of their normal prandial dose of insulin immediately before the meal as a single bolus, with no combo or dual wave boluses allowed. Participants in the exercise carbs group will not administer any prandial insulin or adjust the doses of their basal insulin. The first meal post exercise will be a pre-prepared lunch of sandwiches and fruit (equivalent to 1 g of carbohydrate/kg of body weight) will be provided. Each patient will be provided with a Freestyle Libre reader and sensor to allow interstitial glucose levels to be measured by Flash Glucose Monitor (FGM) throughout the study period. The sensor will be inserted at least 36-48 hours before exercise day to ensure accurate calibration. Due to concerns over a several minute lag between changes in interstitial and blood glucose levels, Capillary Blood Glucose, Ketone and lactate levels will be measured on a calibrated glucometer at baseline and every 15 minutes whilst exercising as well as at baseline, at the completion of the aerobic exercise, and following completion of the 6-min walk test. All treatment decisions will be based on CBG levels and not on FGM and will be administered by the research team in presence of a medical professional (Endocrinologist). All participants data of food intake will be recorded in a case record form for the night before, day of, and for the 48 hours following the study with the details of all meals, snacks and water consumed on a regular basis. Outside of these time frames, they will be allowed to consume their normal diets and there will be no strict and restrictive diet guidelines.