Brits exercising frequently have been warned to be on the lookout for a potentially fatal condition.

Rhabdomyolysis - otherwise known as rhabdo - can produce recurrent abdominal pain which occurs when damaged muscle tissue releases its proteins and electrolytes into the blood.

These can damage the heart and kidneys and cause permanent disability or even death.

Exercising too frequently, jumping headfirst into a particularly tough workout, or not allowing your muscles to heal after intense sets, can lead to rhabdomyolysis.

Crushing injuries, sometimes sustained during exertion but often suffered as a result of falls, can also cause rhabdomyolysis.

Following recent research, NHS says all patients who have lain immobile for indeterminate periods of more than one hour, particularly when drug ingestion, including alcohol, has been possible are at a higher risk of rhabdomyolysis

The same can be said for those who have taken drugs, especially heroin, cocaine and ecstasy. People with sepsis are also at risk due to toxins likely to reach the bloodstream.

The four main symptoms are:

  • Abdominal pain
  • Nausea or vomiting
  • Fever, rapid heart rate
  • Confusion, dehydration, fever, or lack of consciousness

But Professor William O. Roberts, of University of Minnesota, highlighted how exercise leads to the release of kinase, an enzyme critical for metabolism, into blood.

The expert told Runners World: "Almost anyone who works out to improve performance will release or leak some creatine kinase into the bloodstream, but this becomes a problem when the muscle cell releases contents like potassium or myoglobin, which causes complications."

He continued: "It is a bad idea for anyone to surprise muscles with an unexpected volume of work that is well beyond the usual level (which is one of the reasons for the 10 per cent rule), since rhabdomyolysis can lead to renal failure and even death from arrhythmia."

Professor Roberts added: "The likelihood that you would develop rhabdomyolysis is slim unless you are drastically increasing your training volume or intensity, which can cause all kinds of overuse injuries."

According to the NHS' Scottish Muscle Network, cases of rhabdo are rare but are most likely caused by prolonged exertion. This includes falls, prolonged muscle compression, electric shocks, third-degree burns, and "prolonged repetitive exercise with eccentric characteristics, causing muscle tension, strain and injury".

The Centers for Disease Control and Prevention (CDC), based in the States, said that these symptoms can appear any time after a muscular injury.

They added: "For some people, symptoms might not start to appear until several days after the initial injury. If you have any of these symptoms at any time, do not ignore them.

"Seek medical treatment right away. Earlier diagnosis means an earlier start to treatment and a greater chance of recovery without permanent health effects."