Managing blood glucose during and after exercise in Type 1 diabetes: reproducibility of glucose response and a trial of a structured algorithm adjusting insulin and carbohydrate intake

Aims and objectives. To enable people with Type 1 diabetes to exercise safely by investigating the reproducibility of the glucose response to an algorithm for carbohydrate and insulin adjustment during and after exercise compared to their self‐management strategies. Background. Difficulties in managing blood glucose levels in Type 1 diabetes whilst exercising is known to deter people from exercise. Currently there is a limited evidence base to aid health care professionals enable people with diabetes to exercise safely. This study seeks to address this gap. Design. A quasi‐experimental study was undertaken amongst people with Type 1 diabetes. Methods. Over 14 days, 14 participants undertook four exercise sessions (40 minutes at 50%VO2max). Two sessions were undertaken in week 1 self‐managing their diabetes and two sessions in week 2 using an algorithm for carbohydrate and insulin adjustment. Results. The mean reduction of glucose levels detected by Continuous Glucose Monitoring during exercise was 3·1 (SD 2·03) mmol/l. Time spent within the range of 4–9 mmol/l during exercise was not significantly different between the self‐managed and the algorithm weeks (−3–22·4 min). The mean reduction of blood glucose for each individual over all four exercise sessions ranged between 0·8–5·95 mmol/l. The technical error between days one and two was 2·4 mmol/l (CV = 33·2%) and between days 3–4 the technical error was 2·7 mmol/l (CV = 33·7%). Conclusions. The results provide useful data about the reproducibility of the blood glucose response to moderate intensity exercise, despite the variability of individual responses 40 minutes of moderate intensity exercise decreases Continuous Glucose Monitoring glucose by 3 mmol/l with or without a 30% decrease of insulin before exercise. Relevance to clinical practice. This information provides valuable baseline information for people with diabetes and health care professionals who wish to encourage physical activity and undertake further research in this area.