Experts say severe muscle damage, mitochondrial problems and microclots may explain impact of working out

Many people with long Covid feel tired, unwell and in pain for lengthy periods after exercise, and researchers say they now know why.

Experts say they have evidence that biological changes are to blame, such as severe muscle damage, mitochondrial problems and the presence of microclots in the body.

“It’s really confirming that there is something inside the body going wrong with the disease,” said Dr Rob Wüst, an author of the study at Vrije Universiteit (Free University) Amsterdam.

Long Covid is thought to affect tens of thousands of people in the UK alone, and many experience a worsening of symptoms for weeks after a single bout of exercise.

Published in the journal Nature Communications, the study involved 25 patients with long Covid who reported experiencing malaise after exercising, and 21 people who had had Covid but made a full recovery. None of the participants had been hospitalised with Covid, while all had been fit and healthy before catching the virus and were of working age.