In type 1 diabetes (T1D), some few studies have explored the impact of training on glycaemic fluctuations. However, no research aimed to assess glycaemic excursions and their progression throughout a 2-month training program, distinguishing those observed around exercise sessions from those of non-exercising days.

Nineteen (13 female) adults with T1D participated in 2-3 supervised exercise (aerobic/strength) 90-min weekly sessions over 2 months. Glycaemic excursions (continuous glucose monitoring) were calculated for specific periods (24-hour, nocturnal; periods before, during, after exercise sessions) and compared between day with and without an exercise session. Linear mixed models or binary/multinomial logistic regressions with random effects were used to assess the effect of weeks of training and type of day, including or not an exercise session, on glycaemic excursions. The data made available on data.gouv corresponds to all the data files used for these analyses. Access to the data can also be requested from Elsa Heyman.

During the 2-month training, nights following exercise showed reduced risk of hyperglycaemic (>10.0mmol⋅L-1) compared to non-exercise nights. This difference attenuated with weeks of training, in parallel to a progressive increased risk of time >16.7mmol⋅L-1 during early and late recovery periods after exercise sessions. Overall, independently of exercise session occurrence, level 1 and 2 nocturnal hypoglycaemic risk increased as the training weeks passed.

In conclusion, for patients with type 1 diabetes who engage in regular physical activity, it is crucial to be vigilant about post-exercise glycaemic excursions, particularly at night. Although acute exercise (i.e., day with vs. without a training session) reduced nocturnal hyperglycaemia without increasing the risk of hypoglycaemia, this risk of hypoglycaemia progressively increased after several weeks of training, during the nights, even those not subsequent to an acute exercise. Therefore, enhancing glycaemic control, especially at night, using continuous glucose monitoring systems is essential, not only during the first weeks of training, but also after several weeks.