P373 Left atrial mechanics and aortic stiffness following high intensity interval training: a randomised controlled study

Abstract Background Physical inactivity is associated with an increased risk of cardiovascular disease. High intensity interval training (HIIT) has been shown to improve important health parameters, including aerobic capacity, arterial blood pressure, cardiac autonomic modulation and left ventricular mechanics. However, adaptations in left atrial (LA) mechanics and aortic stiffness remain unclear. Therefore, the aim of the present study was to assess any left atrial and aortic adaptations to HIIT. Methods Forty-one physically inactive males and females (aged 23 ± 2.7 years) volunteered for the study. Participants were randomised to either a 4-week HIIT intervention (n = 21) or 4-week control period (n = 20). The HIIT protocol consisted of 3 x 30-second maximal cycle ergometer sprints with a resistance of 7.5% body weight, interspersed with 2-minutes of active unloaded recovery. Speckle tracking imaging of the left atrium and M-Mode tracing of the aorta was performed pre and post HIIT and control period using commercially available software (EchoPac; GE Medical Systems). Analysis of covariance, with baseline measures as the covariate, was used to explore any differences in left atrial mechanics and aortic stiffness between the intervention and control groups. Stepwise linear regression analysis using LA stiffness as the dependent variable was conducted. Results Following 4-weeks of HIIT, there was significant improvement in LA mechanics, including LA reservoir (13.9 ± 13.4%, p = 0.033) and LA stiffness (-0.05 ± 0.04%-1, p = 0.032) compared to the control condition. In addition, improvements were observed in aortic distensibility (2.1 ± 2.7 cm2 × dyn×-1 × 103, p = 0.031) and aortic stiffness index (-2.6 ± 4.6, p = 0.041) compared to the control condition. In stepwise linear regression analysis, aortic distensibility change was significantly associated with LA stiffness change (p = 0.002), with an R2 of 0.613. Conclusion A short-term programme of HIIT was associated with a significant improvement in LA mechanics and aortic stiffness. These adaptations may have important health implications and contribute to the improved left ventricular diastolic and systolic mechanics, aerobic capacity and reduced arterial blood pressure previously documented following HIIT.