💓 Sport does not affect the left and right sides of the heart in the same way

Sport does not only strengthen the heart. It could also modify the nerves that regulate its beats.

Researchers at the University of Bristol studied a still poorly understood mechanism. They observed how regular aerobic exercise acts on small clusters of nerves located near the neck and upper chest.


These clusters are called the stellate ganglia. They are part of the sympathetic nervous system, which prepares the body for action. When we run, are afraid, or experience stress, it helps the heart beat faster and send more blood to the muscles.

The study, published in Autonomic Neuroscience, was conducted on rats. After ten weeks of moderate exercise on a treadmill, the researchers examined these ganglia in three dimensions. They then discovered that the right side and the left side did not change in the same way.

In the trained rats, the right stellate ganglion contained many more neurons than the left. In contrast, the neurons on the left side had become larger. The total volume of these nerve clusters also decreased after training. This shows that exercise does not only transform muscles, but also certain nerve commands to the heart.

This difference between the right and left sides could be important. The right side primarily affects the heart's natural rhythm, while the left side influences a part of the left ventricle more. The researchers therefore believe that these changes could help understand why certain cardiac treatments work better on one side than the other.

For now, this is an early study conducted in animals. Research in humans will be necessary before drawing medical applications. But these results indicate that the automatic nervous system of the heart is more flexible than previously thought. In the long term, this could help better treat certain arrhythmias, chest pain, or stress-related disorders.