Background and Aims
There are limited reports of the performance of the Minimed 670G hybrid-closed loop (HCL) during prolonged continuous effort. The aim of this report was to assess the performance of the HCL in maintaining time-in-range and avoiding hypoglycemia during mountain trail running races.
A type 1 diabetic recreational athlete wearing the HCL system participated in two marathons and one half-marathon. Time-in-range (TIR), average sensor glucose (ASG) and hypoglycaemia were analysed during the entire races, first 2h and remaining hours (only marathons). Carb supplementation was used to prevent/treat lows and replenish energy stores.
No hypoglycemia was recorded. Time-in-range for the marathons (10h47’ and 6h15’) and half-marathon (2h23’) was 83%, 79% and 19%, with ASG of 143.3 mg/dl, 143.8 mg/dl and 232 mg/dl, respectively. During the first 2h of the marathons, TIR and ASG were 68% with 153.96 mg/dl and 52% with 184.36 mg/dl, respectively. During the rest of the races, TIR and ASG were 87% with 140.64 mg/dl and 92% with 123.67 mg/dl, respectively.
The 670G HCL avoided hypoglycemia during all races. Longer races correlate with an increase of TIR and decrease of ASG. Race difficulty (positive level difference, speed, route) impacts the loop’s ability to maintain glycemia in range. High intensity intervals overshoot glucose levels and cannot be rapidly countered by the algorithm. Certain strategies (insulin bolus at the start of race) are required to prevent hyperglycemia resulting from the adrenalin rush at race start. The HCL dramatically reduces hyoglycemia risk during prolonged continuous physical activity while increasing TIR.