Study Finds Muscles Send Chemical Signals to the Brain During Exercise

Growing evidence supports the idea that exercise is beneficial for both the body and mind.

According to a new study published in the journal Neuroscience, the relationship between physical activity and brain health may be even more closely linked.

Researchers examined how the chemical signals produced by muscles during movement lead to neuronal development in the brain. More specifically, they looked at how exercise affects the hippocampus.

The hippocampus is the part of the brain that is involved with the storage of long term memory.

"This study is the first to try to get at the underlying mechanism by which physical activity or exercise may affect the brain. It has long been known that exercise supports a healthy brain and improves mood and cognition," said Dr. Andrew Newberg, neuroscientist and director of research at the Marcus Institute of Integrative Health and a physician at Jefferson University Hospital. "This study shows that there may be chemical signals released by muscle cells that have an effect on neurons. So this study gets at a deeper molecular level related to this effect."

Ki Yun Lee, a PhD student in mechanical science and engineering at the University of Illinois Urbana-Champaign and the study's lead author, told Healthline, that the study shows how chemical from the muscles can impact key parts of the brain including the neurons in the hippocampus.

"Exercise is known to improve cognitive health by changing hippocampal neurons in the brain," Ki Yun Lee, a PhD student in mechanical science and engineering at the University of Illinois Urbana-Champaign and the study's lead author, told Healthline. "Our study provides new insights into how chemical signals from contracting muscles in vitro can accelerate the maturation of hippocampal neurons and promote the formation of neuronal networks."

This study highlights the critical role of astrocytes, specialized cells that surround and support neurons in the brain, in regulating the development of hippocampal neuronal networks.

By highlighting the critical role of astrocytes in regulating the activity of neurons, which are often overlooked in brain research, the study suggests that developing new treatments for neurological disorders may require considering not only neurons but also astrocytes.

Lee pointed out that in the study the team found that removing astrocytes from cell cultures resulted in neurons becoming "hyperexcitable" which can be defined as when a neuron is more likely to be activated by a stimulus.

In at least one 2022 study published in Translational Psychaitry, researchers found that "abnormally elevated neuronal activity" is a common feature of Alzheimer's disease and appears to be associated with greater cognitive decline.

The new study findings could "have important implications for understanding and treating neurological disorders, such as epilepsy, which is caused by hyperexcitability of neurons," said Lee.

Treating astrocytes could involve exploring approaches that target astrocytes to regulate their activity and prevent hyperexcitability in neurons, potentially opening up new avenues for treating neurological disorders, Lee added.

Newberg pointed out that more research is needed to verify these early findings, but the research is interesting.

"The overall finding is that hippocampal cells that are central to brain networks mediating cognitive function and memory are affected by the muscle cells via astrocytes which are important support cells in the brain," Newberg explained. "This complex cascade shown in this study suggests how the brain reacts to exercise."

The study's results support the growing body of evidence that exercise is not only beneficial for physical health but also for cognitive health.

Specifically, the results suggest that chemical signals from contracting muscles may trigger a signaling pathway that enhances cognitive function and may have therapeutic potential for treating neurological disorders.

Additionally, "the findings have significant implications for the development of new approaches to enhance cognitive health and treat neurological disorders," said Lee. "By identifying the critical role of astrocytes in mediating the effects of exercise on hippocampal neurons, the study suggests that future research should consider the interaction between muscles, astrocytes, and neurons."

The study's findings may also inform the development of exercise regimens that are specifically designed to target the interaction between muscles, astrocytes, and neurons for optimal cognitive health, Lee added.

"This study supports the importance of exercise as part of a brain health program for patients," said Newberg. "However, important clinical questions (as well as mechanistic ones) would ultimately be what types of exercise are most effective – aerobic vs anaerobic – and how much and for how long?"

According to new research, exercise enhances parts of the brain including neuronal activity in the hippocampus.

The results of this study suggest that chemical signals from contracting muscles may trigger a signaling pathway that improves brain function and could potentially be beneficial for treating neurological health conditions.

In terms of the next steps, it is recommended to look at the types of exercise that are most effective – aerobic vs anaerobic – examining frequency and duration.