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SINGAPORE - A number of hospitals here have generally seen an uptick in the number of rhabdomyolysis cases in recent times.

Singapore General Hospital's (SGH) emergency department saw the average number of monthly exertional rhabdomyolysis - a breakdown of muscle from extreme physical exertion - cases increase from four in 2020 to 10 last year.

Rhabdomyolysis is essentially the breakdown of muscle tissues and the resultant leakage of its content into blood circulation could cause serious complications, including kidney failure or even death.

The condition may occur due to several reasons, including crush injuries, alcohol, or drug abuse.

A few factors that can increase one's risk of rhabdomyolysis include over-exertion during exercise, inadequate hydration or nutrition and exercising when one is ill or on certain medications.

Medical experts believe that one reason for the upward trend in exertional rhabdomyolysis cases could be linked to the pandemic, which has resulted in extreme changes to exercise habits for some.

Dr Benjamin Ang, a consultant at the department of orthopaedic surgery at SGH, said: "The pandemic has likely increased the number of people getting into fitness, including many who were previously inactive. Restrictions in group numbers may have also resulted in a change in the type of exercise people do. These may have contributed to the increase in the number of cases."

Even though all strenuous exercises can theoretically lead to rhabdomyolysis, it usually occurs in those who are unaccustomed to such exercises, and over-exert themselves, said Dr Mong Rupeng, a senior consultant at Changi General Hospital's (CGH) department of emergency medicine.

He added that the condition seldom hits those who do endurance runs or road cycling. But the popularity of spin cycling, however, has seen young patients suffering from exertional rhabdomyolysis.

While CGH was unable to ascertain whether there has been an increase in the number of cases at the hospital, Dr Mong said that the rhabdomyolysis cases at its emergency department typically involve "young adults presenting with severe thigh pain or passing dark brown urine several days after their first spin class".

There are certain factors that may contribute to rhabdomyolysis occurring more among beginners at spin classes as compared to other forms of cycling.

Dr Mong said: "Compared to outdoor cycling, external factors that may decrease the sustained intensity of exercise such as the need to turn, avoid obstacles or stop for traffic are removed in spin cycling.

"Spin cycling is done in a comfortable air-conditioned environment free of obstacles, where participants are kept engaged with loud and fast tempo music. Projected videos and dimmed lights during the session serve as encouragement to participants to push themselves harder. There may also be pressure to 'ride with the pack'."

Common symptoms of rhabdomyolysis include severe muscle aches, weakness or swelling in affected muscles and red or brown discolouration of the urine.

There are also other less common symptoms such as generalised body aches, fever, rapid heart beating at rest, as well as nausea and vomiting.

Dr Benjamin Soh, a registrar at Khoo Teck Puat Hospital's (KTPH) department of sports and exercise medicine, also highlighted that not all individuals with the condition experience symptoms.

In such cases, additional blood and urine testing can help to confirm whether the patient is suffering from rhabdomyolysis.

While Dr Soh noted that rhabdomyolysis related to strenuous conditions is "fairly rare" as compared to those caused by trauma, he also offered advice on certain precautions individuals can take to reduce the risk of developing the condition.

One such way is to start slow and progress gradually when it comes to exercise.

He said: "Being good at one type of exercise does not necessarily mean you will automatically be good at all types. Always take several sessions to familiarise yourself and build tolerance to the specific exercises you will be doing."

Other precautions include avoiding exercising under extremely hot and humid conditions, wearing light and non-restrictive clothing as well as staying hydrated during exercise.

One should also avoid exercising when unwell and/or taking cough and cold medicines, which can reduce sweating.

SGH's Dr Ang stressed the need for both participants and instructors to be educated and aware of the ways to prevent exertional rhabdomyolysis, which include adequate rest and recovery in between sessions.