Effects of High Intensity Interval Exercise on Blood Pressure

Xiaoyu Wei

【Abstract】This paper reviews the effect of high intensity interval exercise on blood pressure and discussed the mechanism of decreasing blood pressure.

【Key words】High intensity interval exercise; Blood pressure; Effect

【作者簡介】Xiaoyu Wei， Beijing Institute of Technology， Zhuhai.

Complications of high blood pressure have accounted for 9.4 million of death caused by cardiovascular disease in the worldwide every year （1）. Research has proved that the risk of vascular death begins with BP levels as low as 115/75 mmHg and doubles for each 20/10 mmHg rise in systolic/diastolic BP （2）. As such， researchers have invested great effort to prevent diseases related to high blood pressure or hypertension， which is a kind of major health problems that have received a great amount of attention since a few decades ago.

Although hypertension is claimed as a global public health crisis， suitable training and daily exercise may contribute to decreasing blood pressure （1）. The main effect of exercise is generally known as post-exercise hypotension （PEH）， which describes the prolonged decrease in resting BP during the recovery period after exercise （3）. PEH usually occurs after low to moderate intensity endurance （4） and resistance exercise programs （5）. These programs can often be achieved through regular endurance and resistance physical activity with low to moderate intensity.

However， Levinger and colleagues （6） reported that 60% of adults could not meet the minimum-recommended level of regular physical activity. Hence， “no time” could be one of the main barriers for adhering in regular low to moderate intensity exercise programs （7）. Researchers have recently recommended the high intensity interval exercise （HIIE）， which is defined as vigorous exercise performed at a high intensity for a brief period of time， separated by 1-5 minutes of recovery at complete rest or low-to-moderate intensity （8）.

Research has shown that HIIE is more efficient compared to low to moderate intensity exercise （6）. Except that empirical evidence has shown the benefit of HIIE to improve cardiorespiratory and metabolic function （8）， studies have also explored the benefit of HIIE in decreasing BP （3， 9， 10， 11）.

As discussed above， the phenomenon of a prolong BP decreases after HIIE is described as post-exercise hypotension （PEH）. Researchers have proved that PEH can be influenced by different exercise intensities and duration. Ciolac and colleagues （12） found that HIIE was more effective compared with the exercise of lower intensity in reducing SBP and DBP after 16 weeks of training， supporting the importance of HIIE in decreasing BP. On the contrary， other researchers proposed that the magnitude of PEH after HIIE were similar to the intensity of another group with a bout of moderate intensity endurance exercise （3）. Despite arguable results， it is agreed that exercise intensity will significantly change the magnitude of PEH （9）. In addition， researchers used various criteria （i.e. different time points） for measuring BP after HIIE， which might be another cause of the inconsistent results from the literature （3）. Among the studies that had different findings， BP value had been recorded using various criteria. For example， some studies involved total observation of BP within two hours with an interval of 15 minutes （10） or 30 minutes （13） between each record; other researchers involved one hour observation with an interval of 30 minutes （3）. Still， others measured the BP values at special time point， i.e. the 30th minute （14） or the 60th minute （15）. Regarding chronic HIIE， researchers often compared the recorded BP values sampled certain time point， i.e. 24 hours （16） or 72 hours （17） after the intervention with the pre-intervention BP value. The various measurement criteria could be the cause of the inconsistent PEH responses among previous studies.

Although effort was made to examine the mechanism of PEH， researchers only managed to clarify a number of factors that caused the phenomenon of PEH. Hypertension can cause a decrease in endothelial function， which has a role in releasing of nitric oxide. Nitric oxide （NO）， in turn， has an important influence on vasodilation in which decreases BP. Exercise increases the production of NO， which lays one of the potential reasons that cause PEH. Another reason is the decrease of total peripheral resistance （TPR） （18）.

PEH is also related to sympathetic nervous system inhibition and an adjustment in the baroreflex （19）. During exercise， the sympathetic nervous system expands vessels in the non-working muscles; in consequence， the dilation of these muscles adds to the sustained vasodilation potentially. After exercise， sympathetic nervous system turns into deactivate status， which causes continuous vasodilation during the PEH. Baroreflex is another reason that causes PEH in order to keep BP at the homeostatic level. After exercise， the decrease in baroreflex， which results from baroreceptors resetting， causes the phenomenon of PEH（19）.

Overall， HIIE is proved to produce prolong decrease of BP after exercise. Other than the effect of HIIE on BP during and after exercise.

To conclude， although PEH can be influenced by a lot of factors， the optimal level of intensity on lowering of BP is still not clear. Additionally， there is a need to explore more precise measurement criteria. Meanwhile， evidence has supported that measurable decrement of BP can be achieved after HIIE， still， methods of HIIE vary from each other and more empirical evidence is need in order to provide further insights on a particular form of HIIE， namely the acute repeated all-out sprint training. Notwithstanding the fact that HIIE is beneficial for lowering BP， the possible risk of HIIE in BP during exercise is still arguable， hence pointing to the need for examining the changes of BP during HIIE.

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