Exercise rewires the heart, according to new findings that show regular activity physically reshapes the nerves that govern cardiac function and reveals a previously unseen left-right difference in the body.
Researchers at the University of Bristol reported that moderate aerobic training alters the structure of nerve cells that regulate the heart. The changes were sharply asymmetric between the two sides of the body. The study, published in Autonomic Neuroscience, could inform more precise approaches to treating arrhythmias, certain chest pain syndromes including angina, and stress-induced “broken-heart” syndrome.
The discovery was made in rats, so confirmation in people is required. Even so, the work offers a fresh view of how physical activity influences the autonomic nervous system that keeps the heart operating.
Exercise rewires the heart through autonomic nervous system changes
Exercise Changes the Heart’s Hidden Control System
The autonomic nervous system, which oversees essential functions such as heartbeat, breathing, and digestion, helps the heart accelerate during exertion or stress. Small clusters of nerve cells known as the stellate ganglia, located on both sides of the lower neck and upper chest, send signals that affect heart rate and other aspects of cardiac activity.
The new analysis indicates that routine exercise remodels these nerve hubs in ways not previously recognized.
Study lead author Dr. Augusto Coppi, Senior Lecturer in Veterinary Anatomy at the University of Bristol, said the work points to a hidden left-right pattern in the body’s autopilot for the heart. He described the stellate ganglia as acting like a dimmer switch and said regular, moderate activity appears to remodel that switch differently on each side, which could help explain side-specific responses to some therapies and guide more targeted care in the future.
Just 10 Weeks of Exercise Produced Striking Nerve Changes
To examine exercise effects, scientists studied rats that completed 10 weeks of moderate aerobic training, a category that includes brisk walking, swimming, and cycling.
The project involved collaborators from University College London, the University of São Paulo, and the Federal University of São Paulo.
Using stereology, a three-dimensional quantitative method, the team assessed the number, size, and distribution of nerve cells within the stellate ganglia.
The trained animals showed a notable left-right imbalance. The right stellate ganglion that supplies cardiovascular control contained about four times as many neurons as the left, differing markedly from untrained animals. Cell sizes shifted in opposite directions as well. Neurons on the left nearly doubled in size, while those on the right became slightly smaller.
These results suggest exercise does not act uniformly on all cardiac-control nerves. Instead, it drives distinct structural adaptations on each side, offering clues to how the nervous system adjusts to regular activity.
Could the Discovery Lead to Better Heart Treatments?
The findings may be relevant for conditions tied to abnormal nerve input to the heart. Arrhythmias involve heartbeats that are too fast, too slow, or irregular. Angina typically reflects inadequate blood flow to the heart muscle. Stress-induced “broken-heart” syndrome is a sudden weakening of heart muscle often triggered by intense emotional or physical stress.
Some patients are treated by reducing excessive nerve signals to the heart. Approaches include stellate ganglion nerve blocks, which temporarily interrupt signaling, and denervation procedures that disrupt selected pathways.
A clearer understanding of left-right differences in the stellate ganglia could help physicians decide which side to target for the most benefit. Dr. Coppi said mapping how exercise changes these paired nerve hubs offers clues that could one day refine nerve blocks or denervation. He emphasized the results are early-stage and based on rats, and that clinical studies would be needed.
What’s Next for Exercise and Heart Research?
Although the anatomical changes were substantial, their precise effects on heart function remain to be determined.
The team plans to test whether left-right remodeling of the stellate ganglia alters cardiac behavior at rest and during exertion. Researchers also aim to look for similar patterns in other animal models and, ultimately, in humans.
For human work, the group hopes to use noninvasive markers to assess nerve activity without surgery or tissue sampling. If comparable left-right differences are confirmed in people, the discovery could support more personalized treatments for arrhythmias, challenging angina cases, and stress-induced “broken-heart” syndrome. Dr. Coppi said the next step is to link structure to function and to evaluate whether similar remodeling appears in larger animals and humans.