578-P: Effect of Two Timings for Postprandial Exercise Onset on Hypoglycemic Risk in Adults Living with Type 1 Diabetes

Introduction: To limit hypoglycemic risk of during postprandial aerobic exercise the importance of reducing prandial insulin dose have been established with exercise starting 90-min after the meal. People with type 1 diabetes also exercise closer or further away of their mealtime and hypoglycemic risk associated with those timings may be different.

Objective: We aimed to evaluate the effect of two different timings for exercise onset (60-min vs. 120-min post-meal) during moderate intensity exercise.

Methods: 37 participants (25 M/ 12 F; HbA_1c: 7.4 ± 0.9%) received an ultra-rapid insulin dose reduced by 50% and performed 1 hour of continuous moderate intensity exercise (at 60% of VO_2peak) started either 60-min (EX60min) or 120-min (EX120min) after breakfast. Venous blood glucose was measured every 10-min during exercise.

Results: Decrease in blood glucose between exercise onset and nadir (lowest point during exercise) was more important with EX120min (-68.5 ± 43.2 mg/dL, EX60min vs. -75.7 ± 39.6 mg/dL, EX120min, p=0.015). The number of hypoglycemic events during exercise and during recovery (90-min post-exercise) were similar between EX60min and EX120min (3 vs. 4 and 3 vs. 0, respectively). Postprandial glucose excursion before exercise onset was reduced with Ex60min compared to Ex120min.

Conclusion: For postprandial aerobic exercise, with a reduced insulin meal bolus, hypoglycemic risk is comparable if exercise is started at 60 or 120min after the meal. Guidelines established with exercise starting 90min after the meal can probably be used for earlier or later timing.