Exercise doesn't just strengthen the heart. It rewires it

Researchers from the University of Bristol (UK) found, for the first time, that regular aerobic training changes the heart's controlling nerves differently on the left and right sides of the body. The study, published in Autonomic Neuroscience, uncovered a striking left-right difference that may one day improve treatment strategies for irregular heartbeats, chest pain, angina, and stress-induced 'broken-heart' syndrome.

Study lead author Dr. Augusto Coppi, Senior Lecturer in Veterinary Anatomy at the University of Bristol, said: "The discovery points 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. 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."

Exercise Alters Heart-Control Nerves

The project was carried out in collaboration with University College London (UCL) in the UK, the University of São Paulo (USP), and the Federal University of São Paulo (UNIFESP) in Brazil. Using advanced three-dimensional imaging techniques known as stereology, the team examined how exercise changed nerve clusters that help regulate heart function.

After 10 weeks of training, rats that exercised had about four times as many neurons in the cardiovascular nerve cluster on the right side of the body compared with the left, relative to untrained animals. At the same time, neurons on the left side nearly doubled in size, while those on the right became slightly smaller. These findings suggest that exercise remodels the heart's nerve network in different ways on each side.

Potential Benefits for Heart Treatments

Dr. Coppi explained: "Irregular heart rhythms, known as arrhythmias, stress-induced 'broken-heart' syndrome, and certain types of chest pain are often treated by dialing down overactive stellate ganglia - the paired small nerve hubs in the lower neck/upper chest area that send 'go faster' signals to the heart.

"By mapping how exercise changes these ganglia on each side, the study offers clues that could one day fine-tune procedures like nerve blocks or denervation to the side most likely to help. The findings are early-stage and in rats, so clinical studies would need to follow."

Although the research is still in its early stages and was conducted in rats, the results raise the possibility that future therapies could be tailored to target one side of these nerve clusters more effectively than the other. That approach could improve treatments for arrhythmias, stress-induced 'broken-heart' syndrome, and difficult-to-treat angina.

Next Steps for the Research

The researchers now plan to investigate how these structural changes affect the heart's performance both during exercise and at rest. They also intend to determine whether the same left-right pattern appears in other animal models and in humans using non-invasive markers.

Dr. Coppi added: "Understanding these left-right differences could help us personalize treatments for heart rhythm disorders and angina. Our next step is to test how these structural changes map onto function and whether similar patterns appear in larger animals and humans."