Regular exercise is widely known for strengthening the heart and supporting cardiovascular health. However, scientists have discovered that physical activity may do something less obvious: change the physical structure of the nerves that control how the heart works.
Researchers at the University of Bristol in the United Kingdom found that moderate aerobic exercise can reshape small clusters of nerve cells that help regulate heart activity. Surprisingly, the changes were not the same on both sides of the body. Instead, the left and right nerve clusters responded differently after regular training.
Published in Autonomic Neuroscience on October 26, 2026, the study offers a new perspective on how exercise influences the nervous system. Although the experiments were conducted in rats, the findings could eventually help scientists develop more precise approaches to treating certain heart conditions, including irregular heart rhythms and some forms of chest pain.
The Heart Has Its Own Network of Nerve Controls
The heart does not operate independently. Its activity is partly regulated by the autonomic nervous system, a network of nerves responsible for controlling automatic bodily functions such as heartbeat, breathing, and digestion.
One branch of this system increases heart rate when the body needs more oxygen. This happens during physical activity and stressful situations, when the heart must respond to changing demands.
An important part of this control system is a pair of small nerve clusters called stellate ganglia. Located on both sides of the lower neck and upper chest, these structures send signals that influence heart rate and other aspects of cardiovascular function.
They essentially help regulate how strongly the heart responds to signals from the nervous system.
According to Dr. Augusto Coppi, a senior lecturer in veterinary anatomy at the University of Bristol and the study’s lead author, these nerve clusters act like a dimmer switch for the heart. The researchers wanted to understand whether regular physical activity could change the structure of these important nerve centers.
Just 10 Weeks of Exercise Changed the Nerve Cells
To investigate the effects of exercise, researchers examined rats that completed 10 weeks of moderate aerobic training. Aerobic exercise includes activities that increase breathing and heart rate, such as brisk walking, swimming, and cycling.
The study involved scientists from the University of Bristol, University College London, the University of São Paulo, and the Federal University of São Paulo.
Rather than examining heart muscle alone, the team concentrated on the nerve cells within the stellate ganglia. They used an advanced technique called stereology, which allows researchers to examine the number, size, and distribution of cells within biological tissues.
The results revealed that exercise was associated with substantial structural differences between the two sides of the body.
In the trained rats, the right cardiovascular nerve cluster contained approximately four times as many neurons as the left cluster. This was a striking difference compared with the pattern observed in rats that had not undergone the exercise training.
The nerve cells also changed in size, but in opposite directions. Neurons on the left side nearly doubled in size, while those on the right became slightly smaller.
These observations suggest that the nervous system does not necessarily adapt uniformly to exercise. Even nerve structures that regulate the same organ can undergo different physical changes depending on their location.
Related: 8 Dangerous Things That Can Happen When You Exercise Angry
Why the Left and Right Nerves Responded Differently
One of the most interesting aspects of the research is the difference between the two stellate ganglia.
Both structures help regulate heart activity, but the study found that moderate exercise was associated with distinct changes in each one. The right side showed a substantially higher neuron count in trained animals, while the left side experienced a greater increase in individual neuron size.
This suggests that the body’s automatic control of the heart may be more complex than scientists previously understood.
Dr. Coppi explained that identifying these differences could help researchers better understand why certain treatments targeting the nerves around the heart may produce different results depending on which side is treated.
However, the study does not establish exactly why the two nerve clusters responded differently. Researchers still need to investigate how these structural changes influence the actual signals sent to the heart.
That distinction matters because changes in the number or size of nerve cells do not automatically show how effectively those cells regulate heart function.
Could the Findings Improve Treatment for Heart Conditions?
The discovery could eventually affect several conditions involving abnormal nerve activity around the heart.
One example is arrhythmia, a condition in which the heart beats too quickly, too slowly, or irregularly. These disturbances can affect how efficiently the heart pumps blood.
Another condition is angina, which causes chest pain or discomfort typically associated with insufficient blood flow to the heart muscle.
The researchers also highlighted stress-induced broken heart syndrome, a condition involving sudden weakening of the heart muscle that can follow intense emotional or physical stress.
In some patients, treatment involves reducing excessive nerve signals reaching the heart. Doctors may use procedures such as stellate ganglion nerve blocks, which temporarily interrupt activity in these nerve clusters, or denervation, which disrupts certain nerve pathways.
Understanding the differences between the left and right stellate ganglia could eventually help physicians determine which nerve pathways are most appropriate to target in particular patients.
For example, if further research shows that one side plays a larger role in a specific condition, this knowledge could help guide treatment decisions.
Dr. Coppi noted that the findings could eventually help fine-tune procedures such as nerve blocks and denervation. However, he emphasized that the research is still in its early stages and was conducted in rats.
Scientists Still Need to Confirm Whether Humans Experience the Same Changes
Despite the interesting findings, researchers cannot yet conclude that exercise produces identical nerve changes in people.
The team plans to investigate how these structural differences affect heart function at rest and during physical activity. They also intend to examine whether similar patterns appear in other animal models before moving toward studies involving humans.
For human research, scientists hope to identify noninvasive markers that could provide information about nerve activity without requiring surgery or tissue removal.
If similar left- and right-sided differences are eventually confirmed in people, the findings could contribute to more targeted approaches for treating certain heart rhythm disorders and difficult-to-manage angina.
For now, the research adds another dimension to what scientists know about physical activity and cardiovascular health. Exercise may influence more than the heart’s ability to pump blood. It may also reshape parts of the nervous system that help control every heartbeat.
Did you know that regular exercise could physically change the nerves controlling your heartbeat, and does this discovery change how you think about the benefits of staying active?
