Acute effects of exercise at different intensities on mood and brain function

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Abstract

Over the last three decades, studies have demonstrated the enormous importance of physical activity for certain diseases such as heart disease, stroke, diabetes and various oncological ones. Exercise can be used preventively as well as positively influence the progression of the diseases.
In addition, exercise improves mental health, quality of life, and well-being. Mental health in particular plays an important role in everyday life, as a mental imbalance can have a negative impact on many aspects of life, such as school/work, social contacts, etc. Current literature shows that the positive effect of exercise on mood and affect can be detected after a single training session, as well as after weeks/months of training. Even in patients with depression and anxiety disorders an exercise-induced decrease of typical symptoms could be proven. However, the neural basis of these exercise-induced mood changes is poorly understood. For this reason, the present cumulative thesis investigates the effects of acute endurance exercise of different intensities on mood and brain function.
For this purpose, healthy male recreational athletes were recruited (N = 22, age: 27 ± 4 years, height: 182 ± 6 cm, weight: 78 ± 7 kg) and examined using functional magnetic resonance imaging (fMRI) before and after a 30-minutes exercise session on a treadmill. The fMRI included both a task-based fMRI, in which subjects were asked to match emotional (happy, fearful, and neutral) faces, and a resting state fMRI. Subjects underwent three different conditions (low, high, and self-selected intensity) in randomized order on different days, of which, however, only the low and high intensity conditions are the subject of this thesis. In addition to the fMRI scans, a mood questionnaire was acquired (Positive and Negative Affect Schedule; PANAS).
The study aimed to investigate the following: the acute effect of training sessions of different intensities 1) on mood, 2) on functional connectivity (FC) of resting state networks in the brain, 3) on FC in the emotional brain at rest and their correlation with changes in subjects' mood, 4) on the processing of emotional faces.
One of the main findings of this study is that training sessions of different intensity affect FC in different resting state networks (publication 1). On the one hand, low-intensity exercise induced increased FC in cognitive resting state networks such as the right fronto-parietal network, namely in the superior frontal gyrus. On the other hand, a high-intensity training session had a stronger effect on FC in the affective network (right affect and reward network), which showed increased FC in the right insula.
Specific examination of FC in the emotional brain at rest (publication 2) revealed significant FC changes after the high-intensity training session only, namely, an increase in FC between bilateral amygdala and right anterior insula. This change in FC was additionally correlated with the PANAS positive affect scale, which showed an increase in positive mood after both conditions (low and high intensity). The correlation analysis revealed that only changes induced by high-intensity exercise correlated with each other: The increase in positive mood correlated with the increase in FC between the bilateral amygdala and the right anterior insula. This correlation could not be demonstrated after the low-intensity training session.
When examining brain activation with a task-based fMRI (publication 3), which involved identity matching of subjects with different emotional expressions, significant effects were exclusively found for processing fearful faces. A decrease in activation in the right and partially left caudate nucleus, and in the right ventral anterior putamen could be observed after the high-intensity training session, whereas a significant decrease in activation in the posterior cingulate gyrus/precuneus could be observed after the low-intensity training session.
This thesis provides first evidence how exercise at different intensities modulates neuronal activity in the context of exercise-induced mood changes in recreational athletes. The results of this work clearly indicate emotion-specific effects as well as different modulation mechanisms following low and high training intensities and provide a better understanding of the relationships between neural changes and behavioral level changes. The low and high training intensities have different effects on the attentional/cognitive and affective/reward networks. The effects of different intensities can be demonstrated both at rest and during task-related activations in the brain. The demonstrated correlation between subjectively recorded changes in mood and objectively recorded changes in FC in emotion-related brain regions confirms the involvement of amygdalar-insular FC for affective modulation.
Patient studies showed that adults with depression characteristically have weakened FC between the amygdala and insula at rest. Publication 1 and 2 provides the first evidence of how exercise might counteract the characteristic FC changes in affective disorders. It is possible that these effects are mediated by the release of endogenous opioids, as positron emission tomography studies of ligand activation have demonstrated local exercise-induced opioid release in the anterior insula after exercise. Furthermore, affective disorders such as anxiety disorders and depression are characterized by disturbances in face processing.
In publication 3, it was shown that exercise can modulatory interfere with the neural processes of face processing, especially for faces with negative emotional expression. These effects should be experimentally validated in patient populations in the future. This information will then help to use exercise as a therapeutic tool to prevent and/or treat affective disorders. However, this is not just about treating disease, but also about the potential to improve mood and stress resilience in healthy populations.
Original languageEnglish
Place of PublicationKöln
PublisherDeutsche Sporthochschule Köln
Number of pages99
Publication statusPublished - 2022

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