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.

Automated summary

Under hyperinsulinemic conditions, exogenous glucose requirements to maintain stable blood glucose levels increase with exercise intensity, but plateau after moderate to high-intensity exercise (>65% VO2 peak), indicating that high-intensity exercise does not confer protection against hypoglycemia.