12min/week of high-intensity interval training reduces aortic reservoir pressure in individuals with metabolic syndrome: a randomized trial

Objective: Decreased aortic reservoir function leads to a rise in aortic reservoir pressure that is an independent predictor of cardiovascular events. Although there is evidence that high-intensity interval training (HIIT) would be useful to improve aortic reservoir pressure, the optimal dose of high-intensity exercise to improve aortic reservoir function has yet to be investigated. Therefore, this study compared the effect of different volumes of HIIT and moderate-intensity continuous training (MICT) on aortic reservoir pressure in participants with the metabolic syndrome (MetS). Methods: Fifty individuals with MetS were randomized into one of the following 16-week training programs: MICT [n¼ 17, 30 min at 60–70% peak heart rate (HRpeak), five times/week]; 4 4-min high-intensity interval training (4HIIT) (n¼ 15, 4 4 min bouts at 85–95% HRpeak, interspersed with 3 min of active recovery at 50–70% HRpeak, three times/week); and 1 4-min high-intensity interval training (1HIIT) (n¼ 18, 1 4 min bout at 85–95% HRpeak, three times/week). Aortic reservoir pressure was calculated from radial applanation tonometry. Results: Although not statistically significant, there was a trend for a small-to-medium group time interaction effect on aortic reservoir pressure, indicating a positive adaptation following 1HIIT compared with 4HIIT and MICT [F (2,46) ¼ 2.9, P ¼ 0.07, h2¼ 0.06]. This is supported by our within-group analysis wherein only 1HIIT significantly decreased aortic reservoir pressure from pre to postintervention (pre–post: 1HIIT 33 16 to 31 13, P ¼ 0.03; MICT 29 9–28 8, P ¼ 0.78; 4HIIT 28 10– 30 9 mmHg, P ¼ 0.10). Conclusion: Three sessions of 4 min of high-intensity exercise per week (12 min/week) was sufficient to improve aortic reservoir pressure, and thus may be a time-efficient exercise modality for reducing cardiovascular risk in individuals with MetS.