There are two popular approaches to getting a cardiovascular workout. You can work out at a continuous and moderate-intensity or you exercise at a higher intensity using an approach called high-intensity interval training. Although you may have a preference for one approach to cardio or the other, interval training may offer more benefits for cognition and the health of your brain.
The Facts about Brain Health and Aging
Brain health becomes more of an issue as we age. Research shows that portions of the brain involved in cognitive function, such as the hippocampus and prefrontal cortex, shrink in size with age. Memory also declines, as your brain retrieves information more slowly. Age-related memory issues might show up as problems remembering names or where you placed objects. Some older people also suffer from a condition called mild cognitive impairment (MCI) where their memory impairment is more pronounced but not at the level that you see with dementia. However, they’re also at a higher risk of developing dementia.
In most cases, problems with memory and information retrieval are benign and not due to dementia. Instead, they’re a consequence of normal aging, although it affects people to varying degrees. You’ve probably known people who had a sharp mind even into their 90s. Research also shows that brain volume decreases at a rate of around 5% per decade after the age of 40. Just as muscles shink in volume, the brain does too.
Is there a bright spot to this? Fortunately, there is! Studies show exercise may slow brain aging. Cardiovascular exercise, in particular, is linked with reduced brain aging. You might wonder which has more benefits, continuous exercise at a steady pace or interval training. One study looked at brain track changes when subjects did either continuous exercise or interval-based exercise. The study compared the brain effects of moderate-intensity, continuous exercise, low-intensity continuous exercise, and high-intensity interval training. One of the things they were looking at was how each form of exercise affects neuroplasticity.
What is Neuroplasticity?
Neuroplasticity might be a term you’re not familiar with, however, it’s the ability of nerve cells in the brain to adapt by forming new connections. The connections between neurons, or nerves, within your brain, may strengthen or weaken over time based on input from the outside environment. Just as you can build new muscle tissue and new bone tissue, your brain can “strengthen” in a sense by forming new connections and pathways.
What the Study Showed
According to the study, high-intensity interval exercise may enhance neuroplasticity in the brain more than exercising at a steady, continuous pace – but why? One reason may be that long periods of uninterrupted exercise increase levels of the stress hormone cortisol more than interval training. Because interval training sessions are usually shorter, as brief as 20 minutes, you don’t get a sustained release of cortisol. In contrast, most people who do continuous exercise work out for 45 minutes or longer and that can lead to a more sustained increase in cortisol. Although high-intensity exercise can also boost cortisol release, the effects are shorter-term than what you get from prolonged exercise. When you do interval training, the rest intervals may allow cortisol to drop somewhat, decreasing the likelihood of a sustained rise. Plus, a 20-minute workout should cause less of a cortisol surge than a long, continuous exercise session.
Too Much Cortisol Isn’t Brain Healthy
Why is cortisol a problem? When cortisol is high, it blocks neuroplasticity, thereby reducing the positive cognitive benefits of exercise. Sustained elevation of cortisol for other reasons, such as stress, also harms brain health and cognitive function. One study that looked at the brains of middle-aged adults found those who had higher levels of cortisol in their bloodstream had smaller brain volumes, suggesting that their brains were aging faster. Other factors that can increase cortisol include lack of sleep, certain health problems, extreme dieting, mental stress, and social isolation. So, now you know some things to avoid to preserve the health of your brain and slow brain aging.
Increased Blood Flow to the Brain
Another way aerobic exercise, including interval training, improves brain health is by increasing blood flow through arteries in the brain. These are the lifelines that deliver nutrients and oxygen to hungry brain tissues and their neurons. By supplying neurons with more oxygen, it aids neuroplasticity. One study carried out in cyclists found there was a greater increase in blood flow to the brain in older people when they did interval exercise as opposed to steady-state, continuous exercise.
The Bottom Line
Any kind of exercise that increases your heart rate and boosts blood flow to the brain is beneficial for the health of your brain. Your brain depends on a steady supply of nutrients and oxygen to function. Steady-state aerobic exercise improves oxygen delivery, but high-intensity interval training seems to do it more. Plus, a short, HIIT workout is unlikely to lead to a sustained rise in cortisol, a negative for brain health.
Even if you do only two, short high-intensity interval workouts each week, you’re doing something positive for the health of your brain. You don’t want to do it too often, as that could increase cortisol due to the stress of training hard too often. However, these studies make an argument for adding some high-intensity interval training to your routine if you’re concerned about keeping your brain optimized as you age.
Regardless, make sure that you do some form of exercise that boosts your heart and increases oxygen delivery to your brain and other organs. Don’t forget about strength training either. You need that to preserve muscle mass and strength as you grow older. It all counts!
References:
- Brain Plast. 2018; 4(1): 95–110.Published online 2018 Dec 12. Prepublished online 2018 Sep 3. doi: 10.3233/BPL-180073.
- Neural Plast. 2017; 2017: 8305287. Published online 2017 Jul 30. doi: 10.1155/2017/8305287.
- com. “What Helps Your Brain Age Better: Steady-State Exercise or HIIT Workouts?”
- Med Sci Sports Exerc. 2019 Jul;51(7):1523-1531. doi: 10.1249/MSS.0000000000001924.
- Front Neurosci. 2018; 12: 839. Published online 2018 Nov 14. doi: 10.3389/fnins.2018.00839.
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