Rhabdomyolysis is a serious form of muscle breakdown in which muscle fibres die off quickly and leak their contents into your blood. The best-known sign is dark, cola-coloured urine after extreme exertion. In athletes it sometimes starts after a first spinning class, a heavy hyrox or training in the heat. It's rare, but it is a medical emergency.
Let me be clear: this isn't "just train through it". These symptoms call for quick action, not waiting.
What is rhabdomyolysis?
In rhabdomyolysis, muscle cells break down en masse in a short time. That releases substances such as myoglobin and large amounts of creatine kinase (CK). Myoglobin can strain your kidneys, and that's exactly what makes the condition dangerous (Torres, 2015). The urine turns dark because myoglobin ends up in it.
The difference from ordinary muscle pain lies in the severity. Normal soreness after sport is annoying but harmless. Rhabdomyolysis is fiercer and comes with other signals.
How do you recognise rhabdomyolysis?
The classic three signals are: severe muscle pain, muscle weakness and dark urine. That dark, tea- or cola-coloured urine after extreme exertion in particular is a warning to take seriously. Sometimes the muscles are swollen and hard.
| Risk situation | Warning sign |
|---|---|
| First intense spinning or bootcamp class | Cola- or tea-coloured urine |
| Heavy strength training after a long break | Severe, persistent muscle pain |
| Training in high heat | Clear muscle weakness |
| Dehydration during endurance sport | Passing little urine, nausea |
| Swollen, hard muscles | Confusion or feeling unwell (emergency) |
Which sport situations carry risk?
The risk is higher with sudden, unusual load. Think of your first hard group class, lots of eccentric exercises, or intense training in the heat without drinking well. A combination with certain medicines, alcohol or supplements can also play a role.
If you're just starting or picking things up after an injury, build up calmly. That sounds boring, but it's exactly where these problems arise: too much, too soon.
There's more on how hard training affects your blood in the pillar blood values for athletes.
What happens in your blood?
In rhabdomyolysis the CK value is usually sharply raised, far higher than the ordinary rise after a heavy workout. A doctor also looks at your kidney function and at substances such as potassium, because muscle breakdown can disturb them. So blood here isn't a screen beforehand, but part of the diagnosis.
An ordinary, mildly raised CK after sport is something quite different. You can read the difference from a normal peak in CK value too high. The CK-MB test helps tell where the CK comes from.
What should you do if you suspect it?
If you have dark urine together with severe muscle pain or weakness after extreme exertion, don't wait. Contact your GP or the out-of-hours service, and for severe symptoms or feeling unwell call 112 straight away. In the meantime keep drinking well, unless you feel sick.
This is one of the few sport-related situations where speed really matters. Better to call once too often than too late.
How do you lower the chance of rhabdomyolysis?
The main tip is boring but effective: build up calmly. If you start a new, intense sport or pick things up after a break, do it in measured steps. Your muscles adapt faster than you think, but not in one extreme session.
Also watch heat and fluid. If you train in the warmth or do a long, hard effort, drink enough and listen to your body's signals. Dizziness, nausea or severe muscle pain are reasons to stop, not to push through.
If you use supplements or medicines, know that some can raise the chance of muscle damage. If in doubt, discuss it with your GP or pharmacist. Prevention here is mostly about sensible build-up, not a test afterwards.
Getting started
You don't detect rhabdomyolysis with a routine blood test beforehand. If you want a general view of your health as an active man, the Extended Health Checkup can map a number of markers. For acute symptoms: your GP or 112 first, not a self-test.
References
- Torres PA, Helmstetter JA, Kaye AM, Kaye AD. Rhabdomyolysis: pathogenesis, diagnosis and treatment. Ochsner J. 2015;15(1):58-69. PMID 25829882.
- Brancaccio P, Lippi G, Maffulli N. Biochemical markers of muscular damage. Clin Sports Med. 2008. PMID 18206566.
- Thuisarts.nl. I have muscle pain. Dutch College of General Practitioners.
Disclaimer
Caliberhealth works with BIG-registered doctors who assess your blood results. This article gives general information and is not a substitute for medical advice from a GP or specialist. A blood test is a tool, not a diagnosis in itself. For serious symptoms, contact your GP, or in an emergency call 112.
Author
