Background: Circumstantial evidence suggests that an increase in plasma glucose availability
improves exercise capacity in subjects with type 1 diabetes mellitus. The aim of this study
was to assess exercise capacity in eu- and hyperglycaemic conditions in subjects with type 1
diabetes.
Methods: Eight moderately trained male subjects with type 1 diabetes on continuous
subcutaneous insulin infusion were studied. Using identical insulin infusion rates, the patients
were randomly allocated to perform two stepwise ergometer tests in a eu- and hyperglycaemic
clamp condition. The primary endpoint was the peak power output, secondary endpoints
comprised the rate of perceived exertion, lactate levels, heart rate, and respiratory exchange
ratio.
Results: Eu- and hyperglycaemic clamp conditions were at a plasma glucose concentration of
5.3±0.6 mmol/l and 12.4±2.1 mmol/l, respectively (mean ± SD), and remained stable
throughout the physical exercise. Insulin levels were similar in both condition.
Hyperglycaemia did not result in a significant increase in the peak power output compared to
euglycaemia (mean paired difference of 4.96 W, 95% CI -11.3 to 21.2, p=0.49).
Hyperglycaemia did not significantly impact on the secondary endpoints compared to
euglycaemia. Sensitivity analyses confirmed these results.
Conclusions: In subjects with type 1 diabetes exercise capacity is not influenced by
hyperglycaemia. Comparable levels of lactate and similar respiratory exchange ratio suggest
that an increase in extracellular glucose availability did not translate into increased
intracellular glucose oxidation.
