A lot has been said about the effects of exercise on brain health. Just like diets, exercise patterns are highly susceptible to pop culture’s trends and fads. A huge trend from the last few years is High-Intensity Interval Training (HIIT). You can find these exercise protocols in most gyms and all over the internet. And there is a surprising amount of research on HIIT’s health effects, mostly on cardiovascular health.

What is high-intensity interval training?

HIIT, also called high-intensity intermittent exercise or sprint interval training, is a form of interval training. It’s an intermittent exercise protocol wherein periods of short but intense anaerobic exercise are alternated with less intense recovery periods.

This actually reminds me of intermittent energy restriction diets and, in fact, there is a common anthropologic argument favoring both: the survival of our species has relied greatly on the ability to acquire food; our hunter-gatherer ancestors will most likely have required a high level of physical performance mostly based on intermittent running while hunting for food. Therefore, our bodies may have adapted to such patterns of energetic challenges. Our current sedentary lifestyle has consequently rendered us susceptible to a great deal of diseases.

Physical inactivity is one of the top ten risk factors for poor health, being associated with an increased risk of premature cardiovascular and cerebrovascular diseases. Exercise, on the other hand, is known to benefit the brain by promoting angiogenesis (new blood vessel formation), neurogenesis, and synaptic plasticity, thereby improving cerebral blood flow and metabolism and counteracting age-associated cognitive decline and dementia.

From among the available studies on the health benefits of HIIT, one was particularly eye-catching: a review article on HIIT and cerebrovascular health published on the Journal of Cerebral Blood Flow and Metabolism.

HIIT and cerebrovascular health

As said above, different types of exercise may have a different impact on brain health; optimizing exercise in order to prevent stroke and associated neurovascular diseases would therefore be desirable in that context. This review thus focused on analyzing to what extent HIIT could impact cerebrovascular function.

When compared to moderate-intensity continuous exercise training, HIIT seems to confer similar or even higher metabolic, cardiac, and systemic vascular health benefits, both in healthy and in patients with cardiovascular diseases or hypertension.

In fact, one study has shown that HIIT had twice the effect of moderate-intensity continuous exercise in lowering blood pressure. Given that hypertension is a paramount risk factor for stroke, it seems likely that HIIT may also be beneficial in preventing stroke. However, research on the impact and potential benefits of HIIT on cerebral blood flow are rather scarce. It is unknown whether HIIT may have any detrimental effects on the brain. The potential dangers of HIIT to the brain include any consequences that a rapid increase in systemic blood pressure may have, which include the risk of hyperperfusion injury that could lead to stroke or blood–brain barrier breakthrough. But this is all speculative since there is no clinical research examining the effects of HIIT on the brain.

Still, the study states that patients with neurological pathologies, such as Parkinson’s disease and stroke have already begun using HIIT-based protocols. So far, no adverse effects have been reported for stroke rehabilitation but there are still too few studies to make firm conclusions. Nevertheless, given the relationship between heart disease and stroke it seems likely that the beneficial cardiovascular effects of HIIT may indeed be a benefit for cerebrovascular function.

In the end, regardless of the exercise protocol, what really benefits the brain is to remain physically active.

References

Colcombe SJ, Erickson KI, Scalf PE, Kim JS, Prakash R, McAuley E, Elavsky S, Marquez DX, Hu L, & Kramer AF (2006). Aerobic exercise training increases brain volume in aging humans. The journals of gerontology. Series A, Biological sciences and medical sciences, 61 (11), 1166-70 PMID: 17167157

Lautenschlager NT, Cox K, & Cyarto EV (2012). The influence of exercise on brain aging and dementia. Biochimica et biophysica acta, 1822 (3), 474-81 PMID: 21810472

Lista I, & Sorrentino G (2010). Biological mechanisms of physical activity in preventing cognitive decline. Cellular and molecular neurobiology, 30 (4), 493-503 PMID: 20041290

Lucas SJ, Cotter JD, Brassard P, & Bailey DM (2015). High-intensity interval exercise and cerebrovascular health: curiosity, cause, and consequence. Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism, 35 (6), 902-911 PMID: 25833341

Murray CJ, & Lopez AD (2013). Measuring the global burden of disease. The New England journal of medicine, 369 (5), 448-57 PMID: 23902484

Vaynman S, & Gomez-Pinilla F (2006). Revenge of the “sit”: how lifestyle impacts neuronal and cognitive health through molecular systems that interface energy metabolism with neuronal plasticity. Journal of neuroscience research, 84 (4), 699-715 PMID: 16862541

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