Aim/hypothesis: This study was designed to determine whether type 2 diabetic adolescents have reduced aerobic capacity and to investigate the role of cardiac output and arteriovenous oxygen difference (a-vO(2)) in their exercise response.
Methods: Female adolescents (age 12-18 years) with type 2 diabetes mellitus (n = 8) and type 1 diabetes mellitus (n = 12) and obese (n = 10) and non-obese (n = 10) non-diabetic controls were recruited for this study. Baseline data included maximal aerobic capacity (cycle ergometer) and body composition. Cardiac output and a-vO(2) were determined at rest and during submaximal exercise.
Results: Diabetic groups had lower aerobic capacity than non-diabetic groups (p < 0.05). Adolescents with type 2 diabetes had lower aerobic capacity than the type 1 diabetic group. Maximal heart rate was lower in the type 2 diabetic group (p < 0.05). Exercise stroke volume was 30-40% lower at 100 and 120 beats per min in the diabetic than in the non-diabetic groups (p < 0.05). The a-vO(2) value was not different in any condition.
Conclusions and interpretation: Type 2 diabetic adolescents have reduced aerobic capacity and reduced heart rate response to maximal exercise. Furthermore, type 2 and type 1 diabetic adolescent girls have a blunted exercise stroke volume response compared with non-diabetic controls. Central rather than peripheral mechanisms contribute to the reduced aerobic capacity in diabetic adolescents. Although of short duration, type 2 diabetes in adolescence is already affecting cardiovascular function in adolescents.