Why does exercise become harder the less you do?

The less exercise you do, the more it gets harder. Why? A new study by University of Leeds scientists could explain biology.

Scientists found that a protein called Piezo1 protein acts as a blood flow sensor that indicates to the body how much physical activity is occurring. Doing less exercise could deactivate this protein, causing further inactivity and making exercise more challenging.

Moreover, deactivating this protein reduces the density of capillaries carrying blood to the muscles. Restricted blood flow means activity becomes more complex and can cause a reduction in how much exercise is possible.

Scientists conducted this study in mice, but the Piezo1 protein is found in humans, suggesting the same results could occur. They compared two groups of mice: a control group and a group whose Piezo1 levels had been disrupted for ten weeks.

Walking, climbing, and running wheel activity were observed, with the Piezo1 mice showing a striking reduction in activity levels. This suggests an essential role for Piezo1 in sustaining normal physical activity.

At first, scientists considered whether the Piezo1 mice were less interested in exercise. But later, they found no significant differences in the amount or duration of activity between the two groups. Instead, they identified fewer running wheel revolutions per exercise session and slower running speed.

Lead author Fiona Bartoli, a Postdoctoral Researcher at the University of Leeds’ School of Medicine, said: “Exercise protects against cardiovascular disease, diabetes, depression, and cancer. Unfortunately, many people fail to exercise enough for reasons such as injury and computer usage. This puts people at more risk of disease. The fewer people exercise, the less fit they become, often leading to a downward spiral.”

“Our study highlights the crucial link between physical activity and physical performance made at this level by Piezo1. Keeping our Piezo1s active by exercising may be crucial in our physical performance and health.”

In the University of Leeds’ School of Medicine, Supervising author Professor David Beech said: “Our work sheds new light on how Piezo1’s role in blood vessels is connected to physical activity. A lot was already known about its role in blood vessel development, but far less was known about its contribution to vessel maintenance in adults.

“Our discovery also provides an opportunity to think about how the loss of muscle function could be treated in new ways: if we activate Piezo1, it might help to maintain exercise capability.”

Journal Reference:

1. Fiona Bartoli, Marjolaine Debant et al. Endothelial Piezo1 sustains muscle capillary density and contributes to physical activity. Journal of Clinical Investigation, 2022; 132 (5) DOI: 10.1172/JCI141775