Long COVID and ME/CFS Are Not Just Deconditioning

A new study by researchers at Amsterdam University more precisely characterized the differences in muscle physiology between individuals with post-exertional malaise (PEM) and healthy controls.

Background:
Post-exertional malaise (PEM) is a symptom of Long COVID and ME/CFS characterized by a severe worsening of symptoms after minimal physical, mental, or emotional effort.

This means any exertion, especially exercise, will worsen their symptoms.

It's known that Long COVID and ME/CFS patients exhibit:
- muscle fiber shrinkage (atrophy)
- lower aerobic exercise capacity
- reduced mitochondrial function
- reduced capillary density

The Problem:
Healthy subjects who experience a physical decline after the cessation of movement (deconditioning) also experience the above physiological features.

The Study:
A new study more precisely compared PEM to the "use-it-or-lose-it" phenomenon known as deconditioning experienced by healthy controls. The goal was to better understand how PEM affects the muscles by using a more rigorous comparison than in prior studies.

Here were their cohorts:
- ME/CFS (26 participants)
- Long COVID (25 participants)
- Healthy controls (24) who were voluntarily bedridden for 60 days (deconditioned).

A muscle in the thigh (vastus lateralis) was biopsied to investigate muscle physiology.

Results:
As many in our audience know, severe fatigue and reduced fitness are not solely due to a lack of physical activity (deconditioning).

PEM and deconditioning damage the body in different ways. For example:
1. Healthy Controls: Muscle atrophy occurred in all 3 muscle fiber types.
PEM: Muscle atrophy occurred in 1 muscle fiber type involved in endurance

2. Healthy Controls: No change in muscle fiber composition.
PEM: They possessed fewer "endurance" fibers (Type I) and more easily fatigued fibers (Type II) compared to healthy controls.

3. PEM: They had fewer capillary vessels supplying the muscle with oxygen relative to deconditioned healthy controls.

4. Healthy Controls: Those on bed rest had a drop in mitochondrial function correlated to reduced fitness.
PEM: Overall fitness was disconnected from mitochondrial function. The inability to exercise is likely driven by other disease factors, such as vascular impairments, rather than by tired mitochondria alone.

Take Home Message:
Patients with Long COVID and ME/CFS are not just "out of shape" from avoiding exercise. Their bodies have intrinsic abnormalities, and they should be treated as unique medical cases with specialized rehabilitation strategies rather than simply being told to exercise more.

Read more here.