Frequent exercise reshapes nerves that control the heart, research shows

Frequent exercise doesn't just strengthen the heart – it also changes the nerves that control it, according to new research which could guide more targeted and effective care for common heart problems.

The study, led by the University of Bristol (UK), shows for the first time that moderate aerobic training reshapes nerves that drive the heart, and affects them on each side of the heart differently. The research is published in the journal Autonomic Neuroscience today (Wednesday, 24 September).

Findings highlighting this marked left-right split could ultimately be used to treat more effectively a range of conditions, including irregular heartbeats, chest pain, angina pain, and 'broken-heart' syndrome.

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."

Dr. Augusto Coppi, Study lead author, Senior Lecturer in Veterinary Anatomy, University of Bristol

The research, in collaboration with the University College London (UCL) in the UK and the University of São Paulo (USP) and Federal University of São Paulo (UNIFESP) in Brazil, used advanced 3D quantitative imaging analysis methods called stereology. Findings showed that trained rats over a 10-week period had around four times more nerves – called neurons – in the cardiovascular cluster on the right-hand side of the body than the left compared to untrained rats. Conversely, the neurons on the left nearly doubled in size while those on the right slightly shrunk.

Dr. Coppi explained: "Irregular heart rhythms, known as arrhythmias, stress-induced 'broken‑heart' syndrome, and certain types of chest pain are often treated by dialling 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."

The researchers are now planning studies to link these structural changes to how the heart actually behaves at rest and during exercise. They will then look for the same left–right pattern in other animal models and in people using non‑invasive markers. This will help ascertain whether targeting one side of the nerve cluster could make treatments such as stellate nerve blocks or denervation more effective for arrhythmias, stress‑induced 'broken‑heart' syndrome, and difficult‑to‑treat angina.

Dr. Coppi added: "Understanding these left-right differences could help us personalise 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."