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New research shows that regular aerobic exercise reshapes the nerves that control the heart, and it does so differently on the left and right sides of the body. Scientists say the discovery could eventually lead to more precise treatments for common heart conditions, including irregular heartbeats, chest pain, and stress-induced “broken-heart” syndrome.
Newsweek contacted the study authors for more information via email.
Researchers from the University of Bristol in the U.K., working with University College London, the University of São Paulo and the Federal University of São Paulo in Brazil, studied how exercise affects the nerve clusters that regulate heart function.
These clusters, known as stellate ganglia, sit on either side of the spine and act as a kind of control panel for the heart.
Using a 3D imaging technique called stereology, the team compared rats that underwent 10 weeks of aerobic training with rats that did not exercise. The results, published in Autonomic Neuroscience, revealed a clear asymmetry.
Trained rats had roughly four times as many neurons in the right-side cardiovascular nerve cluster compared with the left, relative to the untrained animals. At the same time, the neurons on the left side grew to nearly double their original size, while those on the right shrank slightly.
In other words, exercise did not just add or grow nerve cells evenly. It changed the two sides in opposite ways, one growing in number, the other growing in size.
The heart’s left and right nerve clusters are known to play different roles in regulating heart rhythm and blood flow. Doctors already exploit this asymmetry in some treatments, such as surgically interrupting nerve signals on one side of the body to treat certain dangerous heart rhythms. But until now, no one had shown that exercise itself reshapes the two sides differently.
Study lead author Dr. Augusto Coppi, senior lecturer in veterinary anatomy at the University of Bristol, said in a statement that the findings point to “a previously hidden left-right pattern in the body’s ‘autopilot’ system that helps run the heart.”
“These nerve clusters act like the heart’s dimmer switch and we’ve shown that regular, moderate exercise remodels that switch in a side-specific way,” Coppi said. “This could help explain why some treatments work better on one side than the other and, in future, help doctors target therapies more precisely and effectively.”
The study was conducted in rats, and researchers caution the findings are still preliminary. The team now plans to examine how these structural changes affect heart performance, both during exercise and at rest. They also want to find out whether the same left-right pattern shows up in other animals and in humans, using non-invasive tests.
If confirmed in people, the findings could help doctors design exercise programs or nerve-targeted treatments that account for this asymmetry, offering a more tailored approach to conditions such as arrhythmias and angina that are notoriously difficult to treat. The findings add to the long list of benefits already associated with regular exercise.
Reference
Coppi, A., et al. (2026). Asymmetric neuroplasticity in stellate ganglia: Unveiling side-specific adaptations to aerobic exercise. Autonomic Neuroscience. http://dx.doi.org/10.1016/j.autneu.2025.103338.
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