Factors Affecting Reproducibility of Change in Glucose During Exercise: Results From the Type 1 Diabetes and EXercise Initiative

Aims: To evaluate factors affecting within-participant reproducibility in glycemic response to different forms of exercise. Methods: Structured exercise sessions ~30 minutes in length from the Type 1 Diabetes Exercise Initiative (T1DEXI) study were used to assess within-participant glycemic variability during and after exercise. The effect of several pre-exercise factors on the within-participant glycemic variability was evaluated. Results: Data from 476 adults with type 1 diabetes were analyzed. A participant’s change in glucose during exercise was reproducible within 15 mg/dL of the participant’s other exercise sessions only 32% of the time. Participants who exercised with lower and more consistent glucose level, insulin on board (IOB), and carbohydrate intake at exercise start had less variability in glycemic change during exercise. Participants with lower mean glucose (P <.001), lower glucose coefficient of variation (CV) (P <.001), and lower % time <70 mg/dL (P =.005) on sedentary days had less variable 24-hour post-exercise mean glucose. Conclusions: Reproducibility of change in glucose during exercise was low in this cohort of adults with T1D, but more consistency in pre-exercise glucose levels, IOB, and carbohydrates may increase this reproducibility. Mean glucose variability in the 24 hours after exercise is influenced more by the participant’s overall glycemic control than other modifiable factors.