Regular Exercise May Reshape Heart-Control Nerves, Study Suggests

Scientists have long recognized the benefits of regular exercise on cardiovascular health, including lower heart rate and a stronger heart. Now, new research adds another layer to this understanding. A study on rats, published on September 23 in Autonomic Neuroscience: Basic & Clinical, suggests that aerobic workouts may actually reshape part of the body’s nervous system that helps regulate the heart.

Examining the Stellate Ganglia

The research focused on the stellate ganglia, paired clusters of nerves in the neck that play a key role in controlling heart activity. Scientists trained Wistar rats, a commonly used laboratory strain, on a 10-week treadmill program designed to mimic moderate aerobic exercise. Previous studies had shown that this level of training can lower heart rate without affecting blood pressure in rats.

When researchers compared the trained and untrained rats, they found structural changes in the stellate ganglia that were both surprising and asymmetrical. The right-side ganglion showed a large increase in neuron count but smaller neuron size, while the left-side ganglion displayed the opposite trend—larger neurons with fewer changes in number.

Structural and Functional Changes

Scientists used 3D imaging and stereological methods to measure neuron count, neuron volume, and overall ganglion volume. They also tracked cardiovascular data such as systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), and heart rate (HR).

The results revealed:

• Right stellate ganglion: Four times as many neurons in trained rats compared to untrained, but neurons were 1.2 times smaller, suggesting atrophy.

• Left stellate ganglion: Neurons were 1.8 times larger in trained rats, showing hypertrophy, while overall neuron numbers changed less dramatically.

• Ganglion volume: Both sides shrank, with the right shrinking more significantly (1.4-fold smaller) compared to the left (1.04-fold smaller).

• Heart rate: Trained rats averaged 280 beats per minute, compared to 314 bpm in untrained rats, while blood pressure readings remained unchanged.

Under the microscope, both sides showed clusters of neurons separated by nerve fibers, blood vessels, and connective tissue. In trained animals, the connective tissue septa appeared more prominent, suggesting remodeling of the ganglion’s internal structure.

Asymmetry and Neuroplasticity

These results suggest that aerobic exercise induces asymmetric neuroplasticity—changes that differ between the left and right sides of the nervous system. This challenges the traditional belief that exercise-related adaptations occur uniformly across the body. Instead, the study highlights that the autonomic nervous system may fine-tune its responses depending on side-specific roles in regulating the heart.

Clinical Implications

Lead study author Dr. Augusto Coppi, senior lecturer in veterinary anatomy at the University of Bristol, noted that if similar differences are confirmed in humans, clinicians could use this knowledge to refine treatments for arrhythmias, chronic pain syndromes, or dysautonomia. Exercise might even serve as a non-drug “neuromodulator” in cardiac rehabilitation.

“The paper also notes real-world relevance of stellate interventions (blocks/denervation) in human heart rhythm disorders and other conditions, underscoring why knowing which side does what could matter clinically,” Coppi explained in an interview with Healthline.

However, Coppi emphasized that further research is required. Scientists will need to map the nerve wiring, identify the molecular drivers behind these changes, and test whether similar adaptations occur in humans.

Expert Reactions

Dr. Raj Dasgupta, chief medical advisor for Garage Gym Reviews and not involved in the study, described the research as significant.

“Right now, some treatments target the nerves around the heart, and knowing that exercise reshapes them differently on each side could make those treatments more precise and effective,” he said.

Dasgupta also suggested that this discovery could eventually lead to tailored exercise programs that target specific cardiovascular needs. For now, though, he emphasized a simpler message:

“Regular aerobic exercise is still one of the best things you can do for your heart, and this research just gives us another reason why. Beyond that, it’s too early to make medical changes based on this study, but it’s exciting to think about where the science could take us in the future.”