A 35-year-old man does 3-hour workout. Next day, his urine turns dark and he dies of cardiac arrest: Doctor explains what went wrong

A 35-year-old man reportedly died of cardiac arrest after pushing himself through a three-hour workout following months of little or no physical activity. As per a social media post of a doctor, the next day, he developed severe muscle pain and dark-coloured urine, but the symptoms were initially dismissed as something that would improve with rest.

According to a social media post by Dr Priyam, an internal medicine resident, the man’s condition was linked to rhabdomyolysis, a serious form of muscle breakdown that can occur after extreme physical exertion. The condition can release substances from damaged muscles into the bloodstream, potentially causing kidney injury and dangerous changes in blood potassium levels.

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In the case described by the doctor, the man went into cardiac arrest later that night.

What is rhabdomyolysis?

Rhabdomyolysis, often called “rhabdo”, happens when skeletal muscle breaks down rapidly and releases its contents into the bloodstream.

Muscles contain several substances, including myoglobin, creatine kinase and potassium. When muscle fibres are badly damaged, large amounts of these substances can enter the blood.

Myoglobin is normally found inside muscle cells. Once released, it is filtered by the kidneys and can contribute to kidney damage. This is one reason urine may become dark brown, red or cola-coloured during rhabdomyolysis.

The condition can have several causes, including severe injuries, extreme physical exertion, dehydration, overheating, certain medicines, seizures and some underlying medical conditions.

How can a workout trigger rhabdomyolysis?

Exercise itself does not normally cause rhabdomyolysis.

The risk can rise when someone suddenly goes from very little physical activity to intense exercise without allowing the body time to adapt. High-intensity workouts, particularly when combined with heat, dehydration or inadequate recovery, can put significant stress on muscles.

That is why suddenly attempting a long or extremely demanding workout after months of inactivity can be risky.

A person does not necessarily have to be a professional athlete to develop the condition. It can occur after strenuous exercise in people who suddenly push beyond what their bodies are accustomed to.

Why does the urine turn dark?

Dark urine after a hard workout should not automatically be considered normal dehydration.

When muscles break down, myoglobin can be released into the blood and eventually appear in urine. This can give urine a dark brown, red or cola-like appearance. Reduced urine output can also occur when the kidneys are affected.

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The colour change is therefore an important warning sign, particularly when it occurs alongside unusually severe muscle pain, weakness or swelling.

How can rhabdomyolysis affect the kidneys?

The kidneys filter waste products from the blood. Large amounts of myoglobin released during muscle breakdown can damage kidney cells.

Rhabdomyolysis can therefore lead to acute kidney injury or kidney failure, particularly when the condition is severe or treatment is delayed.

Dehydration can make the situation worse because the kidneys have less fluid available to remove waste products from the bloodstream.

How can it lead to cardiac arrest?

One of the most dangerous complications is an abnormal rise in potassium levels, known as hyperkalemia.

Muscle cells contain potassium. When large numbers of muscle cells are damaged, potassium can spill into the bloodstream. If the level rises significantly, it can interfere with the heart’s electrical activity and cause dangerous heart rhythms.

In severe cases, this can result in cardiac arrest.

That explains the chain highlighted by Dr Priyam in the social media post: extreme exertion causes muscle breakdown, damaged muscles release substances including myoglobin and potassium, the kidneys can become injured, and a dangerous electrolyte imbalance can affect the heart.

The exact medical sequence in the reported man's case, however, cannot be independently established from the social media post alone.

What are the warning signs of rhabdomyolysis?

Some symptoms can appear within hours, while others may develop over the following days. Common warning signs include:

• Severe muscle pain or soreness
• Muscle weakness
• Muscle swelling or tenderness
• Dark brown, red or cola-coloured urine
• Reduced urine output
• Unusual fatigue or weakness
• Dehydration

Symptoms may develop one to three days after muscle injury, according to Cleveland Clinic.

The combination of severe muscle pain after strenuous exercise and dark-coloured urine is particularly important and should not be brushed aside as ordinary post-workout soreness.

How is rhabdomyolysis diagnosed?

Doctors can use blood and urine tests to look for evidence of muscle breakdown and complications.

A key blood test measures creatine kinase (CK). CK levels can rise significantly when muscle tissue is damaged. Doctors may also check kidney function and blood electrolytes, including potassium. Urine tests can also help identify myoglobin and other abnormalities.

How is it treated?

Treatment depends on the severity of the condition and the complications involved.

Patients may require intravenous fluids and monitoring of kidney function and electrolyte levels. Severe kidney injury can sometimes require dialysis. Dangerous potassium levels also need urgent medical treatment because of their effect on the heart.

Early treatment can reduce the risk of serious complications.

How can people reduce the risk?

The message from Dr Priyam’s post is particularly relevant to people returning to exercise after a long break: do not try to make up for months of inactivity in a single workout.

Exercise intensity should be increased gradually, giving muscles time to adapt. Rest is also important, particularly after demanding sessions. Staying adequately hydrated and avoiding excessive heat during strenuous exercise can also reduce the risk.

Most post-workout soreness is not rhabdomyolysis. But severe pain, weakness, swelling or dark urine after unusually strenuous exercise should not be treated as something to simply “sleep off”.

The condition is treatable, but recognising the warning signs early can make a significant difference.

(Disclaimer: This article is for information purpose only. The reported case has not been independently verified. The medical information provided is not a substitute for professional medical advice, diagnosis or treatment.)