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 [n=17, 30min at 60-70% peak heart rate (HRpeak), five times/week]; 4x4-min high-intensity interval training (4HIIT) (n=15, 4x4min bouts at 85-95% HRpeak, interspersed with 3min of active recovery at 50-70% HRpeak, three times/week); and 1x4-min high-intensity interval training (1HIIT) (n=18, 1x4min 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 x time interaction effect on aortic reservoir pressure, indicating a positive adaptation following 1HIIT compared with 4HIIT and MICT [F (2,46)=2.9, P=0.07, (2)=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 3316 to 31 +/- 13, P=0.03; MICT 29 +/- 9-28 +/- 8, P=0.78; 4HIIT 28 +/- 10-30 +/- 9mmHg, P=0.10).Conclusion:Three sessions of 4min of high-intensity exercise per week (12min/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.