Named the impact of long-term COVID-19 on exercise

Long Covid causes changes in the body that make exercise debilitating, say the authors of a new study. Experts say severe muscle damage, mitochondrial problems and microknots may explain the effects of training.

Many people with long-term Covid-19 feel tired, unwell and sore for a long time after exercise, and researchers say they now know why.

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

“This really confirms that something is going wrong inside the body with the disease,” says Dr. Rob Wüst, study author from the Vrije Universiteit Amsterdam.

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

The study, published in the journal Nature Communications, looked at 25 patients with long Covid who reported feeling unwell after exercising and 21 people who had Covid but made a full recovery. None of the participants were hospitalized with Covid, while all were fit and healthy before contracting the virus and were of working age.

Each participant spent about 10-15 minutes on the exercise bike, and blood samples and skeletal muscle biopsies were taken a week before and the day after the task.

Despite significant differences between patients, on average people with long Covid had lower physical performance than healthy participants, writes The Guardian.

When the researchers analyzed biopsy samples taken before exercise, they found that long Covid patients had more white fibers in their muscles than healthy participants. The cells of these fibers have fewer energy-producing structures known as mitochondria and fewer capillaries.

The team also found signs that mitochondria in people with long Covid were not working as well as those in healthy participants.

Dr Wüst says the findings partly explain why people with long Covid had lower exercise capacity.

The team also found that people with long Covid had more clumps of a protein called amyloid in their skeletal muscle, although there was no evidence that these “microclusters” were blocking blood vessels, as some researchers had previously suggested.

A comparison of biopsies taken before and after cycling found that mitochondrial function worsened after exercise in patients with long Covid, and these participants had far more post-exercise tissue damage and signs that the body was trying to recover.

“This could explain, for example, the muscle pain that these patients experience after exercise,” says Dr. Wüst.

He said the findings highlight that people with long Covid should not engage in intense exercise.

“This damages your muscles, impairs your metabolism, and may explain why you feel muscle pain and fatigue for weeks after exercise,” Dr. Wüst said.

Professor Betty Raman from the University of Oxford, who was not involved in the study, said her own research suggested mitochondrial dysfunction may play a role in the fatigue experienced by some people with a long history of Covid. The latest research supports the idea that treatments that improve mitochondrial health may be beneficial, she said.

But as Professor Raman notes, this may not be the whole story: “While it is likely that fatigue is associated with these metabolic disturbances, other contributing factors, such as persistent inflammation, may also play a role.”