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HIIT and Hypertension : Improvement of cardiovascular functions

by P. Debraux | 20 March 2018

exercise, sport, health, physical activity, training, HIIT, aerobic interval training, hypertension, flow-mediated dilatation, cardiovascular, heart, life, science

According to the World Health Organization, high blood pressure is responsible for nearly 13% of the world's deaths, more than 7 million deaths a year. Indeed, increased blood pressure is an important risk factor for cardiovascular diseases (including stroke and coronary artery disease). Hypertension is characterized by a systolic blood pressure (when the heart contracts) greater than 140 mmHg and a diastolic blood pressure (when the heart relaxes) greater than 90 mmHg. Many factors influence systolic and diastolic blood pressures, including blood volume, arterial wall compliance, and peripheral resistance.

Physical activity is recommended for the prevention, treatment and control of high blood pressure. It improves various cardiovascular functions (including endothelial function) that result in lowering blood pressure. Nevertheless, the type of exercise and the optimal intensity are not yet clearly defined. High Intensity Interval Training has become very popular over the last few years, either to improve athletic performance or health. But in comparison to moderate intensity continuous training, what impact will it have on high blood pressure ?

The Study

To answer this question, a team of Norwegian researchers compared effects on different cardiovascular functions following high intensity interval training (HIIT) or moderate intensity continuous training (MICT). For this, the researchers recruited 88 patients (39 women and 49 men aged 52.0 ± 7.8 years, and 15 people including 8 women later dropped out) suffering from stage 1-2 hypertension, defined as systolic pressure included between 140 and 179 mmHg and / or a diastolic pressure included between 90 and 109 mmHg. For 12 weeks, three times a week, these patients were divided into 3 groups :

  • HIIT group (n = 25) : At each training session, patients warmed up for 10 minutes at 60% FCMAX and then performed 4 x 4-minute intervals at 90-95% FCMAX while walking or running on a treadmill uphill with 3 minutes of active recovery between each interval at 60-70% FCMAX. The session ended with 3 minutes cool down. The session lasted 38 minutes.
  • MICT Group (n = 23) : At each training session, patients walked or ran at 70% FCMAX for 47 minutes to perform isocaloric training with the HIIT group.
  • Control Group (n = 25) : These patients received the standard recommendations for high blood pressure including the practice of physical activity, but without any supervision.

The blood pressure (systolic and diastolic pressure) and the heart rate were measured before and after the 12 weeks of the protocol for a whole day thanks to a device that measured them every 15 minutes during the day (between 6am and 10pm) and all the 30 minutes during the night (between 22h and 6h).

VO2MAX and maximum heart rate (FCMAX) were assessed on a treadmill. And endothelial function was measured as flow-mediated dilatation in the brachial artery via ultrasound. Endothelium-independent dilatation was measured after administration of 0.5 mg nitroglycerin under the tongue. Echocardiography and total peripheral resistance measurement were also performed. Finally, quality of life was also assessed before and after the protocol.

Results & Analyzes

The main results of this study show that HIIT and MICT allow a significant decrease in systolic blood pressure (12 vs. 4.5 mmHg) and diastolic blood pressure (8 vs. 3.5 mmHg), but the systolic reduction with HIIT was significantly higher (Fig. 1 and 2). In the HIIT group, 28% of patients achieved a reduction in systolic blood pressure greater than 15 mmHg and 36% of patients had a reduction of 5-15 mmHg. The systolic blood pressure of approximately 24% of patients in the HIIT group returned to normal (<130 mmHg). In the MICT group, only 1 person and in the Control group, only 1 person got normal values after the protocol. To compare, a meta-analysis with 10968 participants showed that the reduction in hypertension using a single type of drug was 7.3 to 9.3 mmHg.

Figure 1. Systolic Blood Pressure.

Figure 2. Diastolic Blood Pressure.

Regarding blood flow dilatation, only HIIT improved (+ 4%). Endothelium-independent dilatation induced by nitroglycerin has not changed, implying that HIIT has improved endothelial function. Endothelial function plays a key role in vasodilation, which ultimately reduces blood pressure. A meta-analysis of 5547 participants showed that a 1% increase in blood flow dilatation resulted in a 13% reduction in the risk of cardiovascular events.

Finally, VO2MAX improved significantly in both groups, but significantly more with HIIT in comparison to MICT (15 vs. 5%, respectively). VO2MAX reflects cardiovascular fitness and an increase equivalent to 1 MET reduces the risk of all causes of mortality by 13% in people with hypertension.

Practical Applications

This study shows that HIIT with long intervals (4 x 4 minutes at 90% FCMAX) significantly reduces blood pressure at systolic (12 mmHg) and diastolic (8 mmHg) compared to MICT (4.5 / 3.5 mmHg) . And the level of reduction is similar to some drugs prescribed for hypertension. In addition, HIIT allows a better improvement of VO2MAX. Finally, only HIIT has improved endothelial function that allows better vasodilatation of the arteries. It is probably these improvements (and many others) that can reduce blood pressure.

References

  1. Molmen-Hansen HE, Stolen T, Tjonna AE, Aamot IL, Schjerve IE, Tyldum GA, Wisloff U, Ingul CB and Stoylen A. Aerobic interval training reduces blood pressure and improves myocardial function in hypertensive patients. Eur J Prev Cardiol 19(2) : 151-160, 2012.

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