The SMART B Exercise Study :''The SMART Study''

Following successful completion of a screening visit, participants will attend the laboratory to complete 3 experimental visits during which they will undertake a 45-minute bout of moderate intensity continuous exercise on a bicycle ergometer at ~60% of the individualised VȮ2max. Prior to commencing exercise, participants will consume a standardised low-glycaemic index, carbohydrate-based meal (equating to 0.75g.CHO.kg.bm-1) with, or without, a 25% reduction in their meal-time insulin dose as well as with carbohydrates before or during exercise (according to the randomisation). Venous blood glucose sampling will be taken in 15-minute intervals leading into and after exercise with 5-minute intervals performed during exercise. Samples will be used to retrospectively cross-compare the metabolic, hormonal, and physiological responses between visits. Visits 1 & 2 will be separated by ≥14 days to ensure adequate familiarisation with the AHCL system whilst visits 2 & 3 will be separated by ≥3days. Each participant will undertake 1 screening and 3 experimental visits equating to a total of 80 study visits.

Inclusion criteria

• • Type 1 diabetes ≥2 years.

• HbA1c;

• 58-63 mmol/mol (maximum 30% of participants) OR
• ≥ 64 mmol/mol (minimum 70% of participants)
• Insulin pump treatment ≥12 months
• CGM or isCGM use ≥6 months
• Novorapid use ≥4 weeks
• Carbohydrate counting and use of the insulin pump bolus calculator for most snacks and meals.
• Carbohydrate intake >80 grams per day (assessed by review of intake recorded in the insulin pump during the 2 weeks prior to the screening visit)

Exclusion criteria

• • Breast-feeding, pregnancy or planning to become pregnant.

• Use of anti-diabetic medicine (other than insulin), corticosteroids or other drugs affecting glucose metabolism during the study period or within 30 days prior to study start.
• Use of hybrid closed-loop systems
• Daily use of paracetamol (acetaminophen)
• Alcohol or drug abuse.
• Severe cardiac disease or retinopathy contraindicating HbA1c <53 mmol/mol.
• Other concomitant medical or psychological condition that according to the investigator's assessment makes the person unsuitable for study participation.
• Lack of compliance with key study procedures at the discretion of the investigator.
• Unacceptable adverse events at the discretion of the investigator