Marcos, 29 years old, had always been sedentary. After watching a few workout videos, he decided to start "with everything": in a single session, he did hundreds of squats and push-ups, without breaks and without guidance. The next day, his legs felt sore, which he considered normal. But the pain didn't go away. It got worse. On the third day, his urine was a dark color, almost like cola soft drink, and he started feeling unusual fatigue. He went to the emergency room and received a diagnosis of rhabdomyolysis.

"The data and clinical case cited in this article are fictional and are merely illustrative, serving to facilitate understanding of the topic addressed."

Cases like this are not uncommon, and it is important to understand that the problem is not with physical activity itself. Exercise is one of the most beneficial things that exist for the body. What needs attention is the way certain workouts are done, especially when the body is not prepared for that level of effort.

What is rhabdomyolysis

Rhabdomyolysis is the accelerated breakdown of muscle fibers. When the muscle is injured intensely, it releases substances into the bloodstream that normally stay inside muscle cells, including a protein called myoglobin. In small quantities, the body deals with it well. In large quantities, myoglobin can overload the kidneys and, in more severe cases, lead to acute kidney injury.

There are several possible causes for rhabdomyolysis, such as trauma, use of certain substances, and infections, but extreme physical exertion is one of the most common, especially in untrained people.

Why certain physical activities increase this risk

What usually leads to this condition is not the exercise itself, but the sudden excess. Some factors greatly increase the chance of serious muscle injury:

  • Very intense workouts after a period of inactivity or sedentary behavior
  • Excessive eccentric exercises, such as doing many squats or push-ups in a row without the body being accustomed to it
  • Very long sets of the same movement, without breaks for the muscle to recover
  • Training in very hot environments or with poor hydration
  • High-intensity group classes, when the person tries to keep up with the pace of someone already trained

This explains why reports of rhabdomyolysis appear, from time to time, associated with modalities such as intense functional training, CrossFit, military tests, and even very demanding spinning classes. The modality is not the problem. The problem is the dose of effort applied disproportionately to the person's physical condition.

How the first signs appear

Initially, the symptoms are often confused with common muscle soreness after a workout. That's where the danger lies, because the difference is in the intensity and duration.

The first signs usually include:

  • Muscle pain much stronger than expected, usually described as deep or throbbing
  • Swelling in the affected muscle
  • Intense weakness, to the point of making simple tasks difficult, such as climbing stairs
  • Difficulty moving the affected limb

How the person feels over the days

While common workout soreness improves in one or two days, in rhabdomyolysis the condition tends to worsen. One of the most characteristic signs, and what usually leads the person to seek care, is dark urine, with the color of strong tea or similar to cola soft drink. This happens precisely because of the presence of myoglobin being eliminated by the kidneys.

Along with this, extreme fatigue, nausea, and in more advanced cases, a reduction in the amount of urine may appear, which is already a warning sign for kidney function.

When to seek medical care

Muscle pain after a workout is expected and is part of the body's adaptation process. What is not expected, and deserves quick medical evaluation, is the combination of disproportionate pain, visible swelling, significant weakness, and dark urine. The earlier rhabdomyolysis is identified, the simpler the treatment usually is, which generally involves intravenous hydration to protect the kidneys.

The safest way to train

This does not mean abandoning intense workouts, but rather respecting progression. Increasing the load gradually, staying well hydrated, resting between sets, and listening to the signals your body gives are simple attitudes that greatly reduce the risk. If a new workout causes pain that is very different from usual, it's worth stopping and observing, rather than persisting.

This content is informational in nature and does not replace consultation, diagnosis, or treatment with a healthcare professional. In case of symptoms, seek medical care.

Dr. Rebeca Soares Andrade CRM - GO 39335