Evidence of Left Ventricular Cardiac Remodeling After 6 Weeks of Sprint Interval Training

Sprint interval training (SIT) leads to similar improvements in maximal oxygen uptake (V̇O_2max) and maximal cardiac output as previously reported for traditional endurance training, but the exercise-induced effects on cardiac remodeling are still largely unknown. The aim of the current study was therefore to explore the effects of SIT on cardiac structure and function assessed by echocardiography in relation to, and controlling for, changes in both blood volume (BV) and heart rate (HR). Healthy men and women (n = 28) performed 6 weeks of SIT. V̇O_2max and total BV were measured, and echocardiography was performed before and after the intervention. There was a robust increase in BV (+7.1%; p < 0.001) and V̇O_2max (+10.1%; p < 0.001) and a decrease in resting HR (-3.9%; p = 0.013) following the SIT intervention. Machine-learning-based feature selection and univariate analysis indicated that several measures of left ventricular dimension (+14.3% LVEDV, p = 0.013; +17.4% LVESV, p = 0.018; +12.3% LVSV, p = 0.031), left ventricular diastolic function (MV_A, MV_D-slope, MV_DT), and left ventricular stroke volume (LVOT VTI) were altered by 6 weeks of SIT. When controlling for the exercise-induced changes in BV and HR, left ventricular dimensions remained significantly changed. Our data indicate that several measures of cardiac function are likely only indirectly affected by SIT, driven by increased BV. However, the disproportionate increase in left ventricular size exceeds what can be explained by changes in BV and HR alone, indicating volume-independent structural cardiac remodeling.