This study investigated whether changing when an automated insulin delivery (AID) system raises its glucose target immediately before exercise affects the risk of low blood glucose (hypoglycaemia) in adults with type 1 diabetes. Twenty‑six adults using the Medtronic MiniMed™ 780G AID system completed multiple supervised cycling sessions that varied by intensity (moderate or high), duration (40 or 90 minutes) and time of day (morning or afternoon). For each session the AID temporary target of 150 mg/dL was started either 60 minutes, 20 minutes, at exercise onset, or not set at all; participants avoided a meal bolus for at least three hours before exercise and received small carbohydrate supplements if glucose fell below study thresholds.

Across all conditions the main finding was that time spent in hypoglycaemia (<70 mg/dL) from the start of exercise until two hours after was very low: the median time below range was 0% for every timing strategy and there were no differences in hypoglycaemic event counts between the timing options. Activating the temporary target 60 minutes before exercise did reduce insulin delivered in the two hours before exercise (by about 0.7 units compared with no temporary target), but this smaller insulin exposure did not produce a measurable reduction in short‑term hypoglycaemia in this well‑controlled cohort. Importantly, no severe hypoglycaemia or diabetic ketoacidosis occurred during the study.

The study also found that morning exercise tended to produce smaller falls in glucose than afternoon exercise, and afternoon sessions showed higher rates of hypoglycaemia. This suggests time of day matters: morning, fasted exercise is generally less likely to provoke a large glucose drop than afternoon activity. The authors emphasise practical priorities that remain important for safe exercise with AID systems — avoid a recent meal bolus within ~3 hours of exercise where possible, and use carbohydrate supplementation before exercise according to guidance (the authors underline the value of supplementing at a threshold around 126 mg/dL, particularly for afternoon exercise).

Limitations include use of a single commercial AID system and a participant group with overall good glycaemic control; results may differ in people with less stable glucose, other devices or when a recent meal bolus is active. Nevertheless, the findings reassure that AID systems provide excellent glucose control during and after exercise across a range of target‑setting strategies. Setting the temporary elevated target 60 minutes before exercise remains a sensible precaution because it reduces insulin on board, but if that window is missed exercise need not be abandoned provided other safety measures (no recent bolus, appropriate carbohydrate strategy) are followed.

In short, for adults using an AID system who have not recently bolused for a meal, supervised real‑world style exercise was generally safe regardless of the exact timing of the elevated pre‑exercise target; TT60 is useful but not strictly essential if other precautions are observed.