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Intense exercise has been shown to have negative effects on systolic and diastolic ventricular function in adults. Very little is known about the normal reaction of the growing heart to endurance stress. For this study, 26 healthy children (18 males) with a mean age of 12.61 years (range, 7.92-16.42 years) took part in an age-adapted triathlon circuit. The athletes were investigated by two-dimensional (2D) echocardiographic/speckle tracking, M-mode, pulse-wave Doppler, color Doppler, and color-coded tissue Doppler at 2-4 weeks before and immediately after the race. After the competition, cardiac output increased, mediated by an increase in heart rate and not by an elevated preload, according the Frank-Starling mechanism. Two-dimensional speckle tracking showed a reduced longitudinal strain in the right and left ventricles and additionally reduced circumferential strain in the left ventricle. The late diastolic inflow velocities were increased in both ventricles, indicating reduced diastolic function due to an impairment of myocardial relaxation. Immediately after endurance exercise, systolic and diastolic functions were attenuated in children and adolescents. In contrast to adult studies, this study could show a heart rate-mediated increase in cardiac output. The sequelae of these alterations are unclear, and the growing heart especially may be more susceptible to myocardial damage caused by intense endurance stress.

Cardiopulmonary fitness benefits cardiovascular health. Various studies have shown a strong negative correlation between exercise capacity and arterial stiffness in adults. However, evidence for this connection in children and adolescents is scarce. About 320 healthy children and adolescents (252 male, 14.0±2.1 years) were evaluated with regard to their demographic, anthropometric and hemodynamic parameters, and their peak oxygen uptake. Peripheral and central systolic blood pressures were measured with patients in a supine position using an oscillometric device. Peak oxygen uptake was assessed by cardiopulmonary exercise testing. In multivariate regression, only peripheral systolic blood pressure (β=0.653, P<.001) and body weight (β=0.284, P<.001) emerged as independent determinants for central systolic blood pressure. Body weight therefore determines central systolic blood pressure in children and adolescents rather than measures of cardiorespiratory fitness. The prevention of overweight in childhood is necessary to reduce stiffening of the arteries and delay the onset of cardiovascular disease.

The relationship between cardiorespiratory fitness and arterial compliance in children and adolescents remains controversial. The aim of this study was to assess this association with a quantitative approach. A total of 646 healthy children and adolescents (316 females, age 13.9±2.1 years) were cross-sectionally investigated in seven school settings in and around Munich for their cardiorespiratory fitness and demographic, anthropometric and hemodynamic parameters. Surrogates of arterial stiffness, such as pulse wave velocity (PWV), Augmentation Index normalized to a heart rate of 75 (AI@75), and peripheral and central systolic blood pressures were measured in a supine position using the oscillometric Mobil-O-Graph. Cardiopulmonary fitness was measured by 6-min indoor run tests. After correction for age, sex, body weight, body height, heart rate and mean arterial pressure, controversial findings were produced. PWV increased with higher cardiorespiratory fitness (Beta=0.173; P<0.001), which represented an unfavorable relationship, whereas AI@75 declined with higher cardiorespiratory fitness (Beta=-0.106; P=0.025). Therefore, in contrast to PWV, higher cardiorespiratory fitness seems beneficial for AI@75. The third surrogate of arterial stiffness, central systolic blood pressure, showed no association with cardiorespiratory fitness (Beta=0.066; P=0.052). These controversial outcomes remain almost unchanged when the boys and girls were analyzed separately. Different surrogates of arterial stiffness have different relationships with cardiorespiratory fitness in children and adolescents after correcting for multiple confounders. More research is needed in this field to understand the functioning of the juvenile vessels, and measurements and methodological approaches should be reconsidered.