Background: High-intensity interval training (HIIT) is a time-efficient alternative to traditional prolonged training. In contrast to ample evidence describing the effects of prolonged training, there are few data describing cardiovascular adaptations arising from HIIT interventions. Objectives: The present study aimed to evaluate the effects of HIIT on heart morphology and function in untrained male subjects. Patients and Methods: Twenty-two young men (age = 23.34 ± 2.56 years, weight = 72.47 ± 12.01 kg, and height = 174.10 ± 5.75 cm) were recruited and randomly assigned into control (n = 10) and HIIT (n = 12) groups. Echocardiography was used to evaluate left ventricular mass (LVM), end-systolic volume (ESV), end-diastolic volume (EDV), interventricular septal wall thickness (IVSWT), stroke volume, and ejection fraction (EF). Also, the Bruce treadmill test was employed to estimate VO2max . Results: The HIIT subjects showed a significant increase in EDV (P = 0.001), LVM (P = 0.002), stroke volume (P = 0.003), and EF (P = 0.001). However, there was no change in ESV due to HIIT (P = 0.916). Additionally, following HIIT, IVSWT (P = 0.227), despite exhibiting a slight increase, was not significantly different from pre-training levels. Conclusions: HIIT in previously untrained subjects led to a significant change in left ventricle (LV) morphology, correlating with improvement in aerobic power (VO2max ). Cardiac remodeling was characterized by an increased EDV and a similar increase in LVM.

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