Cardiac remodeling after six weeks of high-intensity interval training to exhaustion in endurance-trained males

High-intensity interval training (HIIT) improves physical performance of endurance athletes, although studies examining its cardiovascular effects are sparse. We evaluated the impact of HIIT on blood pressure, heart rate and cardiac cavities size and function in endurance-trained adults. Seventeen endurance-trained males underwent 24-hour ambulatory blood pressure monitoring (ABPM) and Doppler echocardiography at baseline and after 6 weeks of HIIT. Participants were divided in 2 groups (85% maximal aerobic power (MP); HIIT85 , n=8 and 115% MP; HIIT115 , n = 9) in order to compare the impact of different HIIT intensities. ABPM and cardiac chambers size and function were similar between groups at baseline. HIIT reduced heart rate (55 ± 8 vs. 51 ± 7 bpm; p= 0.003), systolic blood pressure (SBP; 121 ± 11 vs 118 ± 9 mmHg; p = 0.01), mean arterial pressure (MAP; 90 ± 8 vs 89 ± 6 mmHg; p = 0.03) and pulse pressure (52 ± 6 vs 49 ± 5 mmHg; p = 0.01), irrespective of training intensity. Left atrium (LA) volumes increased after HIIT (maximal: 50 ± 14 vs 54 ±14 ml; p= 0.02; minimal: 15 ± 5 vs 20 ± 8 ml; p = 0.01) in both groups. Right ventricle (RV) global longitudinal strain lowered after training in the HIIT85 group only (20 ± 4 vs. 17 ± 3%, p = 0.04). In endurance-trained males, six weeks of HIIT reduce SBP and MAP and increase LA volumes irrespective of training intensity, whereas submaximal HIIT deteriorates RV systolic function.