Abstract:
Maximal exercise capacity may be limited as a result of T2D, irrespective of deconditioning in both adults and adolescents. This may be secondary to central (cardiac) and/or peripheral (vascular) abnormalities. Aims: 1) determine exercise capacity (VO2peak) in a group of adolescents with T2D compared to an obese, non-T2D group and a non-obese control group; 2) to assess cardiac function in these groups with the use of cardiac magnetic resonance imaging (MRI) at rest and during sub-maximal exercise; 3) to assess femoral artery flow (FAF) at rest and immediately post- exercise as a marker of peripheral vascular function. Methods: 13 subjects with T2D, 27 overweight or obese subjects and 19 non-diabetic, non-obese controls, aged 12-20 years were recruited. All subjects performed an incremental exercise test on a cycle ergometer. Body composition was determined using dual-energy x-ray absorptiometry (DEXA). Cardiac and femoral flow MRI images were taken at rest and during or immediately after sub-maximal exercise using a cycle ergometer designed for use in the MRI. Results: Maximum heart rate (HR) achieved was higher in the control group than in the two other groups (p<0.01) despite comparable maximum workloads. There was no difference in cardiac output (CO) indexed for fat free mass (FFM) between groups at rest however, during exercise CO/FFM was lower in the T2D compared to the obese and control groups (p<0.01, p<0.001 respectively). SV increased by 11.1% in the control group, 5.98% in the obese group and 0.76% in the T2D group during exercise. End-diastolic volume (EDV)/FFM was significantly lower in the T2D both at rest and during exercise. During exercise, EDV decreased by 2.1% in the control group, 0.9% in the obese group and 6.1 % in the T2D group. End-systolic volume (ESV)/FFM was lower in the T2D group at rest and during exercise compared to controls (p<0.01). The average FAF/minute and the net forward volume both indexed for FFM were significantly lower in the T2D group post exercise compared to the other 2 groups (p<0.05). Conclusion: Independent of obesity, T2D negatively affects both central and peripheral vascular function during exercise in adolescents. Central causes appear to be secondary to impaired filling and possible diastolic dysfunction, while peripheral blood flow to exercising muscles may also be impaired. Both may hinder one's ability to engage in physical activity.