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Bursts of short intensity exercise followed by short periods of rest during workouts is beneficial for both your physical and mental fitness. Getty Images
  • New research finds that workout routines with bursts of intensity followed by short periods of rest have a positive effect on the brain’s neuroplasticity.
  • Neuroplasticity is a phenomenon that refers to the brain’s ability to adapt to change by altering its functional and structural properties.
  • Researchers say longer bouts of high intensity exercise may increase levels of cortisol in the body enough to interfere with some of the positive benefits from the exercise.

It’s no secret that physical exercise offers a myriad of health benefits. But depending on your goals and your level of physical fitness, the type and duration of exercise you need to meet those goals could differ drastically.

Should you hit the weights for resistance training? Go on a long jog? Yoga?

Whatever your preferred method of exercise, new research from the University of South Australia has found that regularly mixing up your routine can have a positive effect on both your body and your brain.

In a study published in the Journal of Science and Medicine in Sport, researchers reviewed 12 different experiments involving 128 people designed to monitor changes in the brain during bouts of aerobic exercise.

They were particularly interested in the specifics of which types and durations of exercise yielded the greatest changes in neuroplasticity.

In the study, all of the exercise routines involved either a stationary bike or treadmill, but the intensity and time varied.

For example, some used 20 minutes of high-intensity interval training (HIIT) — short bouts of maximum energy expenditure followed by low intensity rest periods. Others used 25 minutes of “moderate intensity” continuous exercise, and another utilized a “low intensity” continuous 20-minute session.

“We found that high-intensity interval training (HIIT), or moderate intensity continuous training, resulted in the greatest benefits for neuroplasticity (as opposed to high- or low-intensity continuous training) in healthy young adults,” said study co-author Ashleigh Smith, PhD, a senior research fellow at the School of Health Sciences at the University of South Australia.

Neuroplasticity is a phenomenon that refers to the brain’s ability to adapt to change by altering its functional and structural properties. When these changes occur, great things tend to happen, like learning and acquiring new skills.

In other words, physical exercise is good for your brain, too.

And while there’s plenty of prior research to indicate this, there’s far less about what types of exercise are actually best for brain health.

Just like you might do bicep curls to focus on building your arm muscles, it appears that there are certain exercise routines that are better for brain health than others.

“Our research shows that engaging in aerobic exercise enhances the brain’s ability to reorganize, called neuroplasticity. This is important because neuroplasticity underlies learning, memory, and recovery from injuries, such as stroke,” said Smith.

However, Smith and her team admit it’s not entirely certain biologically why some aerobic exercise appears advantageous over other forms, although they do have some theories.

Researchers say that the culprit is likely cortisol, frequently referred to as “the stress hormone.”

Cortisol is an essential part of the body’s endocrine system. However, in abundance, cortisol is linked with several common health problems.

Cortisol is associated with stress and it tends to increase during exercise.

Scientists believe that persistent heavy exercise can increase cortisol levels enough to interfere with some of the positive changes from the exercise itself.

They hypothesize that moderate continuous aerobic exercise or interval training allows the body to better control cortisol levels during a workout.

“We suggest the exercise prescriptions that show the greatest benefits for neuroplasticity occur at intensities where… cortisol is maintained at levels that did not block the neuroplasticity response. For example, the spaced breaks within HIIT may allow cortisol to return to levels that did not block the neuroplasticity response,” said Smith.

If you’ve followed fitness trends at all over the past several years, you’ve probably heard the buzz about high-intensity interval training (HIIT).

Research indicates HIIT holds advantages over other forms of exercise for your body as well as your mind.

Dr. Jeffrey Schildhorn, a sports medicine orthopedic surgeon at Lenox Hill Hospital, NYC, told Healthline that there’s a lot more work to be done to understand the effects of exercise on the brain, but that exploring HIIT further seems promising.

“I think there’s a lot of value in what this study gets at. If you look at how exercise can help, there’s a lot of data that suggests that exercise in general — aerobic exercise specifically — is really good for brain development and even enhanced brain activity in people who are fully grown adults,” said Schildhorn.

HIIT tends to burn more calories in a shorter period of time than other forms of exercise and can help speed up weight loss.

Scientists have even studied the effects of HIIT on aging at a cellular level, as they did in research published last year in the European Heart Journal.

The study compared the effects of different forms of exercise, including weight lifting, aerobic exercise, and HIIT on telomere length.

Telomeres are part of human chromosomes, and their length shortens with age. Shortened telomeres are associated with disease and other age-related health problems.

At the end of a 26-week study period, individuals who did aerobic or strength training saw no change in telomere length. The HIIT group saw a “two-fold” increase in length.

“I think there’s truly [a lot] of positives to [HIIT]. I think it’s fantastic for people who are already somewhat trained, somewhat athletic,” said Schildhorn.

For those out there interested in mixing up their workout or learning more about HIIT, there are a lot of options available. Many gyms now offer a variety of HIIT classes, from dance to weight-lifting.

However, in its most basic form, HIIT is just about mixing up high-intensity exercise with periods of rest.

For example, doing 2 hard minutes on an elliptical or jogging, followed by a minute of recuperation, and then repeating this cycle for 20 to 30 minutes.

But, if you’re not hitting the gym regularly, speaking with a personal trainer might be the best — and safest — way to pick up the basics of HIIT before diving in yourself.