Can Long COVID Affect Your Muscles?

Yes. Long COVID can cause muscle weakness, pain, heaviness and unusually rapid muscle fatigue. Some people find that even everyday movements, such as climbing stairs, washing their hair or standing to prepare food, become unexpectedly difficult.

A 2024 study published in Nature Communications found changes in muscle energy metabolism, muscle fibres and signs of tissue injury in a small group of people with Long COVID who experienced post-exertional malaise (PEM).

These findings suggest that muscle symptoms cannot always be explained by being unfit or inactive. However, they do not prove that everyone with Long COVID has muscle damage, or that every ordinary activity causes injury.

Key Facts About Long COVID Muscle Dysfunction

• Muscle weakness and muscle fatigue are not quite the same. You may be able to start an activity but find your muscles cannot sustain it.
• Heavy legs, burning muscles and trembling arms are symptoms people describe, although they can have different causes.
• Research has identified changes in muscle metabolism in some people with Long COVID and PEM.
• Mitochondria may be part of the explanation, but they are not the whole story.
• PEM can cause delayed worsening after physical, mental or emotional effort.
• Normal routine blood tests do not rule out every muscle-related problem.
• There is no proven supplement or exercise programme that reverses the abnormalities identified in the biopsy study.

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When Your Muscles No Longer Feel Like Yours

There is a particular kind of frustration that comes with losing the ability to do something you never used to think about.

Not running a marathon. Not lifting heavy weights.

Something as ordinary as washing your hair.

You lift your arms, begin shampooing, and halfway through your shoulders start to burn. You lower your arms for a moment, hoping they will recover. But when you try again, they feel strangely heavy.

Or perhaps it’s your legs.

You reach the bottom of the stairs and look up. It’s only one flight. You’ve climbed it thousands of times. Yet halfway up, your thighs feel as though they’re carrying weights, and you wonder whether you’ll make it to the top without stopping.

You might still be able to walk. You might even look perfectly well.

But the effort required has changed.

And that can be difficult to explain.

People understand tiredness. They understand sore muscles after exercise.

What they may struggle to understand is why holding a saucepan, drying your hair or standing in the kitchen can feel like a workout.

For some people with Long COVID, the problem isn’t simply feeling tired. It’s that their muscles seem unable to do what they used to do.

That experience has prompted researchers to ask a fascinating question: could Long COVID be changing the way muscles produce energy and respond to exertion?

Why Do My Muscles Feel Weak After Doing Almost Nothing?

Think about how much you ask of your muscles during an ordinary day.

Your legs support you while you stand. Your shoulders and arms work while you get dressed. Your back and neck muscles keep you upright while you sit at a desk.

Most of the time, you barely notice them.

Until you do.

With Long COVID, some people find that muscles become tired much sooner than expected. Others experience pain, heaviness, trembling or a loss of strength.

And sometimes it’s not just one sensation.

Your legs may feel heavy while you’re walking, then begin shaking when you stop. Your arms may ache while you’re cooking, even though you haven’t lifted anything particularly heavy.

There is an important distinction here.

Muscle weakness means your muscles cannot produce their usual force.

Muscle fatigability means they cannot keep going for as long as expected.

Muscle pain is another symptom altogether.

You can experience all three, but they don’t necessarily have the same cause.

If you’re trying to understand the different forms of weakness, our guide to Muscle Weakness and Long COVID explores the symptom in more detail.

For now, let’s look at what scientists have discovered inside the muscles themselves.

What Did Scientists Find Inside the Muscles of People With Long COVID?

In January 2024, a research team in the Netherlands published a study that attracted considerable attention.

Led by Brent Appelman, Rob Wüst and colleagues, the researchers examined muscle samples from 25 people with Long COVID who experienced post-exertional malaise, alongside 21 people who had recovered from COVID-19.

Participants underwent an exercise test, with muscle biopsies taken before and approximately a day afterwards.

The researchers wanted to understand two things: why people with Long COVID had reduced exercise capacity, and what might be happening during PEM.

Their findings suggested that the muscles of some people with Long COVID were behaving differently.

But what does that actually mean when you’re sitting at home, wondering why your legs feel like concrete?

1. Your muscles may struggle to produce energy efficiently

Every movement needs energy.

When you stand up, walk to the kitchen or lift your arms, your muscles need a constant supply of it.

Mitochondria are tiny structures inside cells that play a major role in producing that energy.

You can think of them as part of the machinery that keeps your muscles working.

The 2024 study found alterations in muscle energy metabolism and mitochondrial-related enzyme activity in the Long COVID group.

This is interesting because it offers a possible biological explanation for reduced physical capacity.

But there’s an important limitation.

The study doesn’t mean that everyone with Long COVID has permanently damaged mitochondria. Nor does it mean that taking a supplement marketed for mitochondrial health will repair the problem.

The researchers identified differences that deserve further investigation.

For someone struggling with daily tasks, the significance is simpler: scientists are investigating whether the problem may involve how muscles use energy, not just how much exercise someone has been doing.

2. Some muscle fibres were different

Your muscles contain different types of fibres.

Some are better suited to sustained activity. Others are more suited to short bursts of effort and tend to tire more quickly.

In the Long COVID group, researchers found a greater proportion of fast-fatigable fibres.

Imagine being able to start a task but finding that your muscles lose their capacity much sooner than expected.

That doesn’t prove the fibre changes are responsible for this exact experience, but it gives researchers another possible clue.

It also raises a question that deserves more attention: if the muscle itself has changed, is simply telling someone to exercise more an adequate response?

3. Researchers found signs of muscle tissue injury

This was one of the study’s more striking findings.

The team observed signs of muscle injury and repair, with some abnormalities becoming more apparent after the exercise test.

That may help explain why exertion can be followed by substantial muscle pain and fatigue in some people with PEM.

However, the study involved a maximal exercise test.

It did not show that brushing your teeth, walking to the bathroom or lifting a kettle causes the same tissue injury.

That distinction matters.

When you’re already frightened by what your body can no longer do, research should help you understand your symptoms—not make you afraid of every movement.

The study is important, but it is one small piece of a much larger puzzle.

Research: Appelman and colleagues, Muscle abnormalities worsen after post-exertional malaise in long COVID, Nature Communications, 2024.

Why Do My Legs Feel Like Concrete With Long COVID?

This is one of those descriptions that immediately makes sense to someone who has experienced it.

Your legs aren’t necessarily painful.

They just feel impossibly heavy.

Walking from the bedroom to the bathroom might feel as though you’re moving through thick mud.

Or perhaps your legs work reasonably well for the first few minutes, then suddenly seem to lose their strength.

There isn’t one established explanation for this sensation.

Muscle fatigability may contribute. So might autonomic dysfunction, circulation problems, nerve-related symptoms or other medical conditions.

For example, if the heaviness appears mainly when you’re standing and improves when you lie down, orthostatic intolerance may be relevant.

That’s different from muscles becoming exhausted after repeated movements.

The distinction is worth discussing with your doctor because the most useful assessment may depend on what actually happens.

Our article on Long COVID and Blood Vessels: The Hidden Role of Vascular Dysfunction looks at another part of this complicated picture.

The important point is that heavy legs is a description of how something feels, not a diagnosis.

And finding the right explanation may require looking beyond the muscles alone.

Why Do My Muscles Burn When I Haven’t Exercised?

Perhaps you’ve noticed your arms burning while you wash your hair.

Or your thighs aching after standing for only a few minutes.

It can feel remarkably similar to the sensation you once experienced after a hard workout—except there hasn’t been a workout.

Muscle burning may accompany unusual fatigability, pain or other changes in muscle function.

But the sensation doesn’t tell us exactly what’s happening inside the tissue.

It doesn’t automatically mean lactic acid is accumulating, that mitochondria have stopped working or that muscle fibres are being damaged.

These are possible areas of investigation, not conclusions that can be drawn from how a symptom feels.

If your muscles are becoming progressively weaker, or if pain and weakness are significantly different from your usual Long COVID symptoms, it’s important to seek medical assessment.

Why Can I Manage Something Today but Not Tomorrow?

This may be one of the most confusing parts of living with Long COVID.

One morning you manage to make breakfast, take a shower and spend a little time with your family.

You feel tired afterwards, but perhaps you think you’ve got away with it.

Then the following day arrives.

Your muscles ache. Your legs feel heavier. Your brain is foggy. Even sitting upright may be difficult.

You start replaying yesterday.

Was it the shower? The stairs? Did I stand too long?

This delayed worsening may be post-exertional malaise, or PEM.

And PEM isn’t simply ordinary muscle soreness.

It can affect the whole body, with symptoms worsening after physical, cognitive, emotional or sensory demands.

The 2024 muscle study investigated what happened after physical exertion in people with PEM. It identified changes that may be relevant to understanding the condition.

But it did not establish that every PEM episode is caused by muscle injury.

We’ve explored the experience and timing of PEM in Post-Exertional Malaise in Long COVID: What It Is, What It Feels Like and How to Recognise It.

If you experience both immediate muscle exhaustion and delayed crashes, recognising that they’re not necessarily the same process may help you describe your symptoms more clearly.

Is It Really Just Deconditioning?

This is where the conversation can become painful.

You explain that your muscles no longer tolerate ordinary activity.

Someone suggests that you’ve been inactive for too long.

You need to rebuild your strength.

Of course, being less active for months can affect muscle mass and fitness.

Deconditioning is real.

But that doesn’t mean it explains everything.

The 2024 researchers identified abnormalities that they argued could not be adequately explained by inactivity alone.

Their interpretation has also been challenged in subsequent scientific discussion, which is part of how research develops.

So we need to hold two ideas at once.

Reduced activity can affect muscles. And Long COVID may involve additional biological problems that cannot simply be corrected by pushing harder.

For someone with PEM, this distinction is especially important.

An exercise programme that works for a healthy person recovering from a period of inactivity may not be appropriate for someone whose symptoms become substantially worse after exertion.

Our article Why Exercise May Worsen Long COVID Symptoms explores that issue without repeating it here.

What If My Blood Tests Are Normal?

You describe the weakness.

Your doctor orders blood tests.

The results come back normal.

And yet you still can’t climb the stairs the way you used to.

It’s natural to wonder how both things can be true.

Routine blood tests can help identify certain causes of weakness or muscle injury. They may reveal problems involving thyroid function, electrolytes, anaemia or muscle breakdown.

But they don’t measure every aspect of muscle metabolism.

And the abnormalities identified in a research biopsy aren’t necessarily detectable through standard blood tests.

That doesn’t mean everyone with Long COVID needs a muscle biopsy.

Most don’t.

Muscle biopsies and electromyography (EMG) are specialist investigations used when there’s a particular clinical reason to suspect a muscle or nerve disorder.

What matters is making sure new or progressive symptoms are assessed rather than assuming that every problem must be caused by Long COVID.

A normal result can be useful information. It just may not answer every question.

What Does All This Mean for Everyday Life?

Research papers tend to focus on measurable changes.

Muscle fibres. Enzyme activity. Exercise capacity.

But the consequences of reduced muscle capacity often appear in much smaller moments.

You might find yourself sitting on the edge of the bed after getting dressed, because putting on clothes has taken more effort than you expected.

You may stop cooking meals that involve standing for long periods.

You might hesitate before picking up a child, not because you don’t want to, but because you’re uncertain whether your arms will manage.

Or perhaps you miss the feeling of walking without having to think about walking.

These are changes to independence, confidence and family life.

They also make the usual advice to stay active sound strangely disconnected from reality.

When you are already using much of your physical capacity on basic tasks, exercise is not always an extra activity that can simply be added to the day.

Sometimes the shower is the day’s main physical challenge.

And sometimes even that needs to be divided into smaller steps.

Can You Improve Long COVID Muscle Dysfunction?

This is the question most people want answered.

Not simply what the research found.

But whether things can get better.

Unfortunately, we don’t yet have a treatment proven to reverse the muscle abnormalities described in the 2024 study.

We also cannot use that study to predict an individual’s recovery.

Some people with Long COVID improve over time. Others experience prolonged symptoms or fluctuating levels of function.

What helps one person may not help another.

That uncertainty is frustrating, especially when you’re looking for something practical to do.

But there are ways to make life less physically demanding while researchers continue investigating the underlying biology.

Make ordinary activities easier, not harder

If standing to prepare food is exhausting, sitting may help.

If showering uses too much energy, a shower stool may make the task more manageable.

If carrying shopping leaves your arms shaking, delivery or help from someone else may reduce the physical demand.

These adjustments don’t repair muscle metabolism.

But they can make the difference between completing an essential task and being unable to do anything else that day.

And they may help you reserve some capacity for the things that matter to you.

Think about your total activity, not just exercise

When you’re living with Long COVID, activity isn’t limited to walking or working out.

Getting dressed is activity.

Preparing meals is activity.

Travelling to an appointment is activity.

So is the physical effort of sitting upright for someone with significant orthostatic symptoms.

If you experience PEM, pacing can help you recognise and manage these demands.

Our Long COVID Pacing Guide goes into the practical details.

NICE guidance for ME/CFS recommends flexible energy management and advises against programmes that automatically increase exercise regardless of symptoms. The guidance is specific to ME/CFS, but is relevant when someone with Long COVID also has ME/CFS or a similar PEM pattern.

What about physiotherapy?

Physiotherapy is not automatically helpful or harmful.

The question is what kind of physiotherapy, for whom, and with what understanding of PEM.

Someone who has lost strength without experiencing PEM may have different rehabilitation needs from someone who becomes substantially worse after exertion.

For people with PEM, activity must be approached cautiously and individually, ideally with clinicians familiar with energy-limiting post-viral conditions.

Being told to increase repetitions every week, regardless of how you respond, is not the same as carefully tailored rehabilitation.

Can supplements help your mitochondria?

CoQ10, magnesium and B vitamins often appear in discussions about mitochondrial health.

It makes sense that people would be interested, especially after reading research about impaired muscle energy metabolism.

But there is currently no good evidence that these supplements reverse the muscle abnormalities identified in the 2024 study.

Treating a diagnosed nutritional deficiency is different from taking supplements in the hope of repairing mitochondria.

And supplements can have side effects or interact with medication.

It’s worth discussing them with a clinician or pharmacist rather than assuming that something described as mitochondrial support is automatically beneficial.

When Should Muscle Symptoms Be Investigated?

Long COVID can cause persistent muscle-related symptoms, but it shouldn’t become an automatic explanation for every new problem.

Seek medical assessment if you’re experiencing progressive weakness, frequent falls, new muscle wasting, difficulty performing movements that were previously possible, or symptoms that differ substantially from your usual pattern.

Sudden one-sided weakness, facial drooping or speech changes require emergency assessment.

Severe muscle pain or weakness accompanied by dark urine also needs urgent medical attention.

The aim isn’t to worry about every symptom.

It’s to make sure treatable or urgent conditions aren’t overlooked.

Frequently Asked Questions

Why do my muscles feel so weak with Long COVID?

Long COVID can involve reduced muscle strength or unusually rapid muscle fatigue. Research has identified differences in muscle metabolism and structure in some people with Long COVID and PEM, but other medical causes of weakness also need consideration.

Why do my legs feel like concrete after COVID?

Heavy legs may reflect muscle fatigability, weakness, autonomic symptoms or other problems. The sensation alone cannot identify the cause, particularly if it changes depending on whether you’re standing, walking or resting.

Can Long COVID cause burning muscles?

Some people report muscle burning or pain after relatively little activity. Research is investigating possible muscle-related mechanisms, but the sensation does not prove tissue damage or a particular metabolic problem.

Why do my arms shake when I wash my hair?

Holding your arms up requires sustained muscle activity. Trembling may accompany fatigability or weakness, but it can also have neurological or other causes. Persistent or worsening shaking should be assessed.

Can you have muscle dysfunction with normal blood tests?

Yes. Routine blood tests do not assess every aspect of muscle function. However, normal tests also don’t establish that Long COVID is responsible, and further investigation may be appropriate.

Does Long COVID cause mitochondrial damage?

Studies have identified altered mitochondrial-related metabolism in some groups of people with Long COVID. The causes, extent and long-term significance remain under investigation.

Is Long COVID muscle weakness permanent?

Not necessarily. People follow different recovery paths, and current research cannot reliably predict an individual’s outcome from their muscle symptoms.

Should I exercise to rebuild my muscles?

That depends on your symptoms and medical assessment. If you experience PEM, pushing beyond your limits may worsen symptoms. Exercise and rehabilitation should not follow automatic increases regardless of how your body responds.

Can muscle weakness and PEM happen together?

Yes. You may experience muscle exhaustion during an activity and a broader delayed worsening afterwards. They can overlap but are not necessarily the same process.

Is there a treatment for Long COVID muscle dysfunction?

There is currently no proven treatment that reverses the muscle changes reported in the 2024 biopsy study. Care focuses on investigating other causes, managing symptoms and adapting activity to individual tolerance.

Related Reading: Understanding Muscle Symptoms and Exertion

Different symptoms often overlap in Long COVID. If you’re looking for more detail on a particular part of the experience, these articles may help:

• Muscle Weakness and Long COVID — why muscles may feel weaker or harder to use.
• Post-Exertional Malaise in Long COVID — why symptoms may worsen hours or days after activity.
• Why Exercise May Worsen Long COVID Symptoms — understanding exercise intolerance and the risks of pushing through PEM.
• Long COVID Pacing: How to Protect Your Energy — making everyday activity more manageable.
• Long COVID and Blood Vessels — exploring how circulation and vascular dysfunction may contribute to symptoms.

When the Smallest Things Become the Biggest Challenges

There is something especially difficult about losing confidence in your own muscles.

You used to know what your body could do.

You could carry a bag, walk up the stairs, hold your arms above your head or stand long enough to cook dinner.

Now you may have to think carefully before attempting any of them.

And perhaps what you miss most isn’t exercise.

It’s not having to think about these things at all.

The research into Long COVID muscle dysfunction is still developing. Scientists haven’t explained every symptom or found a reliable way to reverse the abnormalities they’ve observed.

But the work matters because it asks questions that go beyond fitness and motivation.

It asks what happens inside the body when ordinary physical effort becomes extraordinarily difficult.

And for the person sitting halfway up the stairs, waiting for their legs to recover, those questions matter enormously.

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Research and Further Reading

1. Appelman B, Charlton BT, Goulding RP, et al. (2024). Muscle abnormalities worsen after post-exertional malaise in long COVID. Nature Communications. https://doi.org/10.1038/s41467-023-44432-3
2. Ranque B, et al. (2025). Muscle abnormalities in Long COVID. Nature Communications. https://www.nature.com/articles/s41467-025-56430-8
3. Appelman B, et al. (2025). Reply: Muscle abnormalities in Long COVID. Nature Communications. https://www.nature.com/articles/s41467-025-56431-7
4. NICE. Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management (NG206). https://www.nice.org.uk/guidance/ng206/chapter/recommendations

Medical disclaimer: This article is for general information and education, not individual medical advice. Muscle weakness, pain and exercise intolerance can have several causes. New, progressive or severe symptoms should be assessed by a qualified healthcare professional.

Last Update October 2026