Bloomberg The research compared responses to 8-12 minutes of high-intensity cycling in a group of long Covid patients and a group of healthy people. All 46 of the volunteers had blood and muscle biopsies taken before and after for analysis. All of the long Covid patients experienced a bout of debilitating fatigue known as post-exertional malaise. Lab studies showed signs of severe tissue damage, including dying muscle fibers, inflammation, immune activation, and metabolic disturbances in the post-exercise biopsies of patients’ upper leg muscle, but not in those of the healthy controls.
After the exercise test, the energy-producing mitochondria of patients’ muscle cells appeared impaired and there was also an increased accumulation of amyloid-containing deposits, which other studies have found in the blood vessels of long Covid sufferers.
The findings indicate that in people for whom vigorous physical activity brings on post-exertional malaise, or “PEM,” exercise is far from beneficial — it risks causing harm.
“The pathology of PEM is completely different from being physically inactive,” Rob Wust, an assistant professor in muscle physiology, who co-led the study, told me. Sufferers pushing themselves to improve their fitness could be making themselves sicker.