Introduction: Evening-time exercise is a frequent cause of severe hypoglycemia in type 1 diabetes, fear of which
deters participation in regular exercise. Recommendations for normalizing glycemia around exercise consist of
prandial adjustments to bolus insulin therapy and food composition, but this carries only short-lasting protection from
hypoglycemia. Therefore, this study aimed to examine the impact of a combined basal-bolus insulin dose reduction
and carbohydrate feeding strategy on glycemia and metabolic parameters following evening exercise in type 1

Methods: Ten male participants (glycated hemoglobin: 52.4±2.2 mmol/mol), treated with multiple daily injections,
completed two randomized study-days, whereby administration of total daily basal insulin dose was unchanged
(100%), or reduced by 20% (80%). Participants attended the laboratory at ∼08:00 h for a fasted blood sample, before
returning in the evening. On arrival (∼17:00 h), participants consumed a carbohydrate meal and administered a 75%
reduced rapid-acting insulin dose and 60 min later performed 45 min of treadmill running. At 60 min
postexercise, participants consumed a low glycemic index (LGI) meal and administered a 50% reduced rapid-acting
insulin dose, before returning home. At ∼23:00 h, participants consumed a LGI bedtime snack and returned to the
laboratory the following morning (∼08:00 h) for a fasted blood sample. Venous blood samples were analyzed for
glucose, glucoregulatory hormones, non-esterified fatty acids, β-hydroxybutyrate, interleukin 6, and tumor necrosis
factor α. Interstitial glucose was monitored for 24 h pre-exercise and postexercise.

Results: Glycemia was similar until 6 h postexercise, with no hypoglycemic episodes. Beyond 6 h glucose levels fell
during 100%, and nine participants experienced nocturnal hypoglycemia. Conversely, all participants during 80%
were protected from nocturnal hypoglycemia, and remained protected for 24 h postexercise. All metabolic parameters
were similar.

Conclusions: Reducing basal insulin dose with reduced prandial bolus insulin and LGI carbohydrate feeding
provides protection from hypoglycemia during and for 24 h following evening exercise. This strategy is not associated
with hyperglycemia, or adverse metabolic disturbances.


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