Physical inactivity is associated with increased risk of cardiovascular disease and myocardial dysfunction. High intensity interval training (HIIT) has been shown to improve cardiovascular health; however, adaptations of cardiac structure and function are uncertain. Therefore, the aim of the present study was to analyse cardiac structural and functional adaptations to a HIIT protocol.
Forty-one physically inactive individuals (males n=20 and females n=21) were randomised into either a 4-week HIIT intervention or control group. The HIIT consisted of 3 x 30-second maximal cycle ergometer sprints against a resistance of 7.5% body weight, separated by 2-minute active recovery periods. In total, 12-sessions were performed. All cardiac structural and functional parameters were measured by quantitative 2D transthoracic echocardiography, performed using a commercially available, portable ultrasound system (Vivid‐q, GE Healthcare, Milwaukee, Wisconsin) with a 1.5–3.6 MHz phased array transducer (M4S‐RS Matrix cardiac ultrasound probe).
The HIIT intervention produced significant improvements in resting heart rate (65.59 ± 10.15 to 63.05 ± 13.42 b·min-1, P=0.013), stroke volume (55.48 ± 16.27 to 64.24 ± 20.62ml, P=0.015), left ventricular end diastolic volume (115.59 ± 28.34 to 131.94 ± 33.40ml, P=0.025), E/a ratio (1.98 ± 0.48 to 1.95 ± 0.55; P=0.027), average E/e’ ratio (5.41 ± 1.17 to 5.22 ± 0.89; P=0.002) and isovolumetric relaxation time (81.23 ± 12.85 to 77.83 ± 9.81 m·s-1; P=0.022) compared to the control group.
HIIT produced significant improvements in resting haemodynamics and diastolic function. This time efficient exercise intervention produces important improvements in myocardial function in a physically inactive population, which may be of clinical importance in higher risk populations.