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HASSELT, Belgium — COVID-19 could lead to a person’s muscles swelling in size, according to new study of critically ill patients. Researchers in Belgium discovered that some individuals with a severe case of the virus saw their muscle fibers balloon by over 60 percent while in the hospital.

Scientists believe the body’s immune response damages mitochondria, the powerplants of cells, leading to a loss of energy that builds up water — causing muscles to swell. The phenomenon stunned the Belgian team, since muscle shrinkage is a common complication among people spending several days in an intensive care unit.

Biopsies of the most powerful muscle in the thigh from 18 COVID patients revealed the muscles in four of them increased “massively” while in the ICU. The type 1 and type 2 fibers in these patients grew by 62 and 32 percent, respectively.

Researchers explain that type 1 muscle fibers support endurance activities, while the type 2 fibers handle quick and powerful moments.

Lead author Dr. Toon Mostien of Jessa Hospital notes that this kind of swelling can ultimately lead to muscle fibers dying. Since it’s normal for muscle to shrink due to inactivity, the team believes this strange side-effect is a temporary condition.

Overall, type 1 fibers grew by six percent and type 2 shrank by five percent across all of the COVID patients in the study. The team considers this change statistically insignificant.

COVID also leads to severe muscle shrinkage

However, when the study authors excluded the patients with severe swelling from the results, the remaining patients displayed significant muscle shrinkage. In patients without COVID swelling, their type 1 muscle fibers shrank by 11 percent and their type 2 muscles decreased by 17 percent.

The average age of these participants was 69 and the majority were men. The team scanned samples under a microscope for any changes occurring during the first week in intensive care. Typically, bed rest and mechanical ventilation often leads to muscle wastage. It can hamper recovery and affect mobility and quality of life.

Previous research has revealed that fibers shrink by almost a fifth after a week in ICU. The team fears COVID is causing even greater damage. Mostien’s team found the number of capillaries supplying type 1 and type 2 fibers with oxygen and nutrients fell by five and 10 percent, respectively.

“Although the results were not significant, a drop in perfusion of almost 10% could potentially contribute to muscle fiber destruction,” Dr. Mostien says in a media release.

“There are concerns that immune response to Covid can exacerbate muscle wastage, meaning that critically ill Covid patients experience more severe muscle damage than the general ICU population,” the study author concludes. “Given the global burden of COVID-19, it is vital we learn more about this and our research is an important first step.”

Researchers presented their findings at Euroanaesthesia 2021, a virtual meeting of the European Society of Anaesthesiology and Intensive Care.

South West News Service writer Mark Waghorn contributed to this report.

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