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Brain Connectivity Fluctuates Based on Exercise Intensity

High- and low-intensity exercise influence brain networks in different ways.

A new study reports that low-intensity exercise (walking on a treadmill) stimulates brain networks associated with cognitive control and attention. In contrast, the researchers found that high-intensity exercise (running on a treadmill) activates brain networks involved with emotional processing.

Sergey Nivens/Shutterstock
Source: Sergey Nivens/Shutterstock

Both low- and high-intensity physical activity (walking or running) on a treadmill are associated with an uptick in positive mood, according to the researchers. These findings (Schmitt et al., 2019) were recently published in a special issue of Brain Plasticity dedicated to "exercise and cognition."

For this study, researchers at the University Hospital Bonn in Germany used resting-state functional magnetic resonance imaging (Rs-fMRI) to individually assess changes in brain connectivity after walking or running on a treadmill.

On separate days, each of the 25 participants (who were young and healthy recreational athletes) had a brain scan before and after 30-minute bouts of low-intensity (35 percent below lactate threshold) or high-intensity (20 percent above lactate threshold) treadmill-based exercise.

Before and after each bout of physical activity, study participants also completed the Positive and Negative Affect Schedule (PANAS) questionnaire, which measured pre-to-post exercise mood changes. As the authors explain:

"PANAS revealed a significant increase in positive mood after both exercise conditions. Significant effects were observed between conditions in the right affective and reward network (ARN), the right fronto-parietal network (FPN) and the sensorimotor network (SMN).

Pre-to-post comparisons after 'low' exercise intensity revealed a significant increase in rs-FC in the left and right FPN, while after 'high'-intensity exercise rs-FC decreased in the SMN and the dorsal attention network (DAN) and increased in the left ARN."

Anyone who mixes up their workout routines to include both high-intensity interval training (HIIT) and low-intensity physical activity (e.g., casual walking) knows that different intensities of exercise affect how you think and feel.

Throughout history, philosophical thinkers, scientists, and writers have used daily walks to stimulate cerebral brain functions and optimize cognition.

For example, long before we had advanced brain imaging technology, one could speculate that Aristotle created the Peripatetic (i.e., "given to walking about") School in ancient Greece because he understood that students' brains absorb knowledge better during low-intensity physical activity.

In the 19th century, Ralph Waldo Emerson—who lived near Walden Pond in Concord, Massachusetts—said of his next-door neighbor, Henry David Thoreau, "The length of his walk uniformly made the length of his writing. If shut up in the house, [Thoreau] did not write at all."

 Wikipedia Commons/Public Domain
Albert Einstein riding his bicycle.
Source: Wikipedia Commons/Public Domain

In the 20th century, Albert Einstein said of E = mc2, "I thought of that while riding my bicycle."

Knowing that low-intensity exercise activates functional connectivity between brain networks involved in cognitive control and focused attention can serve as a source of motivation for people who hate to exercise but want to think better.

"We believe that functional neuroimaging will have a major impact for unraveling body-brain interactions," lead investigators Angelika Schmitt and Henning Boecker from the Functional Neuroimaging Group at the University Hospital Bonn said in a news release. "These novel methods allow us to 'look' directly into the brains of a group of athletes, and, maybe even more importantly, understand the dynamic changes in brain structure and function associated with the transition from a sedentary to a healthy lifestyle."

 Department of Radiology, University Hospital Bonn, Bonn, Germany.
After low-intensity exercise, Rs-MRI showed that networks in the brain associated with cognitive control/attention were stimulated, while after high-intensity exercise, networks associated with emotions were more active, and those related to fatigue/motor function, decreased.
Source: Department of Radiology, University Hospital Bonn, Bonn, Germany.

In an editorial commentary, "Exercise Effects on Cognitive Functions in Humans," featured in this special issue of Brain Plasticity, guest editors Ozioma Okonkwo and Henriette van Praag write:

"Physical exercise improves memory function and mood, and may delay or prevent the onset of neurodegenerative conditions in older individuals. Understanding the effects of exercise on the underlying structural and functional neuronal mechanisms in the human brain is currently the focus of intense investigation.

This study (Schmitt et al., 2019) is unique in being one of the first to demonstrate differential effects of two individually-titrated exercise intensities on brain connectivity at rest. An important next step would be an elucidation of the potential neurobiological mechanisms underlying these exciting findings."

Hopefully, future research will provide more science-based evidence on how different exercise intensities can optimize cognitive brain functions and improve emotional affect.

Someday soon, experts may be able to prescribe "doses" of HIIT or low-intensity workouts that fortify functional connectivity between specific brain networks in ways that could be tailored to fit someone's day-to-day cognitive and emotional needs.

References

Angelika Schmitt, Neeraj Upadhyay, Jason Anthony Martin, Sandra Rojas, Heiko Klaus Strüder, Henning Boecker. "Modulation of Distinct Intrinsic Resting State Brain Networks by Acute Exercise Bouts of Differing Intensity." Brain Plasticity (First published: December 26, 2019) DOI: 10.3233/BPL-190081

Editorial by Ozioma Okonkwo and Henriette van Praag. "Exercise Effects on Cognitive Function in Humans." Brain Plasticity (First published: December 26, 2019) DOI: 10.3233/BPL-199001

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