Exercise is known to strengthen the heart, but scientists have discovered that it may also reshape the nerves that control how the organ functions. A study involving rats found that just 10 weeks of moderate aerobic exercise produced significant structural changes in nerve clusters responsible for regulating heart activity.

Researchers at the University of Bristol and their partners studied structures known as stellate ganglia, located on either side of the lower neck and upper chest. These nerve clusters are part of the autonomic nervous system, which automatically regulates functions such as heart rate.

The results, detailed in a study appearing in Autonomic Neuroscience, suggest that exercise affects the left and right sides of this system differently. The finding may ultimately help scientists better understand how the nervous system adjusts to regular physical activity.

However, there is an important limitation: the experiment was conducted in rats. Scientists still need to determine if the same changes occur in humans and how they affect heart function.

Exercise Changed the Nerves on Both Sides Differently

After 10 weeks of moderate aerobic exercise, the researchers saw stark differences between the left and right stellate ganglia of the animals.

Trained rats had about four times as many neurons in the right cardiovascular nerve bundle as in the left. The researchers also observed changes in the size of individual nerve cells. Neurons on the left nearly doubled in size while those on the right shrank slightly.

These findings suggest that exercise can produce different kinds of structural changes in the nerves that regulate the heart, rather than having the same effect on both sides.

The finding could eventually have implications for treating conditions involving abnormal nerve signals, including arrhythmias, certain types of chest pain, and stress-induced takotsubo cardiomyopathy, often called broken heart syndrome.

Doctors already perform procedures like stellate ganglion nerve blocks to interrupt nerve signals in select patients. A better understanding of the differences between the left and right clusters of nerves might eventually help doctors decide which side to target in any given case.

Nevertheless, it will still be some time before researchers can apply these findings to change medical treatment. The team hopes to learn how those structural changes affect heart function and if similar patterns can be found in other animals and humans.

For now, the research offers a new view into how exercise may affect the body. The findings don’t prove that 10 weeks of exercise will create the same nerve changes in people, but they give scientists another avenue to pursue the link between physical activity and heart health.