Effect Of Exercise Intensity On Exogenous Glucose Requirements To Maintain Stable Glycemia At High Insulin Levels In Type 1 Diabetes

Context: Under basal insulin levels, there is an inverted U relationship between exercise intensity and exogenous glucose requirements to maintain stable blood glucose levels in type 1 diabetes (T1D), with no glucose required for intense exercise (80% VO2 peak), implying that high-intensity exercise is not conducive to hypoglycemia.Objective: This work aimed to test the hypothesis that a similar inverted U relationship exists under hyperinsulinemic conditions, with high-intensity aerobic exercise not being conducive to hypoglycemia.Methods: Nine young adults with T1D (mean +/- SD age, 22.6 +/- 4.7 years; glycated hemoglobin, 61 +/- 14 mmol/mol; body mass index, 24.0 +/- 3.3 kg/m(2), VO2 peak, 36.6 +/- 8.0 mL.kg(-1) min(-1)) underwent a hyperinsulinemic-euglycemic clamp to maintain stable glycemia (5-6 mmol.L-1), and exercised for 40 minutes at 4 intensities (35%, 50%, 65%, and 80% VO2 peak) on separate days following a randomized counterbalanced study design.Main outcome measures: Glucose infusion rates (GIR) and glucoregulatory hormones levels were measured.Results: The GIR (+/- SEM) to maintain euglycemia was 4.4 +/- 0.4 mg.kg(-1) min(-1) prior to exercise, and increased significantly by 1.8 +/- 0.4, 3.0 +/- 0.4, 4.2 +/- 0.7, and 3.5 +/- 0.7 mg.kg(-1) min(-1) during exercise at 35%, 50%, 65%, and 80% VO2 peak, respectively, with no significant differences between the 2 highest exercise intensities (P > .05), despite differences in catecholamine levels (P < .05). During the 2-hour period after exercise at 65% and 80% VO2 peak, GIRs did not differ from those during exercise (P > .05).Conclusions: Under hyperinsulinemic conditions, the exogenous glucose requirements to maintain stable glycemia during and after exercise increase with exercise intensity then plateau with exercise performed at above moderate intensity ( > 65% VO2 peak). High-intensity exercise confers no protection against hypoglycemia.