Echocardiographic Evaluation of the Effects of High-Intensity Interval Training on Cardiac Morphology and Function

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. The present study aimed to evaluate the effects of HIIT on heart morphology and function in untrained male subjects. 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. 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. 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.