Glycemic control during consecutive days with prolonged walking exercise in individuals with type 1 diabetes mellitus

Aims: Despite its general benefits for health, exercise complicates the maintenance of stable blood glucose concentrations in individuals with type 1 diabetes. The aim of the current study was to examine changes in food intake, insulin administration, and 24-h glycemic control in response to consecutive days with prolonged walking exercise (similar to 8 h daily) in individuals with type 1 diabetes. Methods: Ten individuals with type 1 diabetes participating in the worlds' largest walking event were recruited for this observational study. Simultaneous measurements of 24-h glycemic control (continuous glucose monitoring), insulin administration and food intake were performed during a non-walking day (control) and during three subsequent days with prolonged walking exercise (daily distance 40 or 50 km). Results: Despite an increase in daily energy (31 +/- 18%; p <0.01) and carbohydrate (82 +/- 71 g; p <0.01) intake during walking days, subjects lowered their insulin administration by 26 +/- 16% relative to the control day (p <0.01). Average 24-h blood glucose concentrations, the prevalence of hyperglycemia (blood glucose > 10 mmol/L) and hypoglycemia (blood glucose <3.9 mmol/L) did not differ between the control day and walking days (p > 0.05 for all variables). The prolonged walking exercise was associated with a modest increase in glycemic variability compared with the control day (p <0.05). Conclusion: Prolonged walking exercise allows for profound reductions in daily insulin administration in persons with type 1 diabetes, despite large increments in energy and carbohydrate intake. When taking such adjustments into account, prolonged moderateintensity exercise does not necessarily impair 24-h glycemic control.