Objective: This study examines the association of fitness on glycemic variability (GV) in adolescents with type 1 diabetes mellitus (T1DM). GV has been associated with high frequency of hyper- and hypoglycemia.
Methods: Nineteen adolescents with T1DM, ages 14 to 19 years, underwent aerobic fitness testing to determine their maximal aerobic capacity (VO2 max). A continuous glucose monitoring (CGM) device was placed on each subject and worn for 3 to 5 days until a return visit when the subjects underwent a 1-hour treadmill exercise session. Mean amplitude of glycemic excursion (MAGE) was calculated from the CGM data collected between the 2 study visits. Metabolic equivalent (MET), a measure of accumulated metabolic workload during the exercise session, was also calculated.
Results: Mean VO2 max was 46.6 ± 6.8 mL/kg/min, with a range of 34.8 to 57.0 mL/kg/min. Mean MET during the exercise session was 577.2 ± 102.4 and ranged from 354.3 to 716.2 METs. There was an inverse association between VO2 max and MAGE (r = -0.46; 95% confidence interval [CI], -0.01 to -0.76; P = .048). MET load and MAGE also had an inverse relationship (r = -0.48; 95% CI, -0.03 to -0.77; P = .037).
Conclusion: GV is inversely associated with fitness and MET load. Aerobic fitness should be promoted in adolescents with T1DM not only because of its multiple beneficial effects but also due to a possible association with GV, leading to fewer extremes in hypo- and hyperglycemia.