Rhabdomyolysis in Cyclists is a serious health concern we can avoid through knowledge of the disease and how to prevent it.
Rhabdomyolysis in cyclists is a serious health concern that affects many athletes, virtual cyclists in particular. Unfortunately, several appealing aspects of virtual cycling also carry the danger of experiencing this debilitating disease.
The good news is it is preventable if knowledgeable and sensible, but if not, it may require a prolonged period of inactivity and constant fear of recurrence.
A 2017 study published in The American Journal of Medicine cited that the “high-intensity exercise associated with ‘spin class’ comes with significant risks to newcomers” when describing Spin Class-Induced Rhabdomyolysis as a public health concern.[1]
Rhabdomyolysis-Related Risk Factors of Virtual Cycling
- Highly motivating and fun.
- Ease and convenience of training.
- Availability of high-level competition and racing.
- Efficient training without inherent interruptions.
- Monitoring of fitness data metrics provide visual proof of improvement.
- Ability to start at a high-intensity level without the constraints of bike handling limitations.
- Hot and humid surroundings often with poor ventilation.
What is Rhabdomyolysis in Cyclists?
Rhabdomyolysis is a muscle injury where the muscle fibers break down, leading to several forms of systemic insult, with the most important being acute kidney injury, electrolyte imbalance, and disseminated intravascular coagulation (DIC).
In addition, this muscle injury causes the release of intracellular muscle components, including myoglobin, creatine kinase (CK), aldolase, and lactate dehydrogenase, as well as electrolytes, into the bloodstream and space surrounding muscle cells.
The kidneys are responsible for removing myoglobin and the other muscle components from the blood and flush it out of the body through urine. Myoglobin can damage the kidneys in large quantities, and if the kidneys cannot get rid of the waste fast enough, acute renal failure (ARF) and death can occur.[2]
What is the PREVALENCE of Rhabdomyolysis?
Every year, approximately 26,000 people develop this condition. ARF is the most significant and acutely life-threatening complication of rhabdomyolysis, and an estimated 10%-40% of patients develop ARF. Up to 15% of all cases of ARF are attributable to rhabdomyolysis.
Mortality for intensive care patients with Rhabdomyolysis without ARF is 22% and jumps to 59% in patients that develop ARF.[3]
Billy had been a recreational cyclist for over 25 years and chose to ride in the cool darkness before work. In 2017, at the age of 42, he began riding virtually for safety and convenience.
The fun, motivation, and ability to track his fitness metrics as they improved caused him to become ‘hooked.’
He rapidly ramped up his volume and intensity and even started racing in the hours before work. By September of that year, Billy was racing daily, his fitness was improving, and he had energy leftover for household projects in the humid Louisiana heat.
Billy collapsed while at work following a tough race and was admitted to the hospital, where he suffered severe muscle soreness, prompting doctors to test his CK level to confirm a diagnosis of Rhabdomyolysis.
He spent 3 days in the hospital and a month at home with zero physical activity to recover.
Billy spent the time wisely, motivated by a safe return to his sport, researching the disease and importance of rest days, recovery rides, base-building, and periodization. His hunger for knowledge evolved into certification as a USA cycling coach.
Billy warns, “As good as virtual cycling has been for my health, fitness, and overall wellness, it does have its pitfalls if not approached with caution. I had never cycled with such consistency and intensity to ever worry about recovery. Virtual cycling has made indoor riding so fun and racing so available that it is easy to push past your limits.”
Who is AFFECTED by Rhabdomyolysis?
Although Rhabdomyolysis can happen to anyone, certain groups have a higher risk than others of developing the condition. People with an increased chance of getting rhabdomyolysis to include:
- Endurance Athletes
- Firefighters: Develop the condition after physical exertion in hot temperatures.
- Service members: People in the military, an estimated 38.9 per 100,000 in 2019[4], especially those who are in boot camp or are undergoing intense training, have an increased risk.
Common SYMPTOMS of Rhabdomyolysis in Cyclists
1. Discolored Urine – Dark or tea-colored urine, caused by excessive myoglobin, is often one of the first signs of a problem.
2. Muscle Pain and Tenderness – Muscle pain and soreness is a primary symptom of exercise-induced rhabdomyolysis.
3. Localized and General Muscle Weakness – Muscle weakness can force the muscles to work harder than usual to carry out basic tasks and people with rhabdomyolysis often experience general fatigue and lethargy.
4. Decreased Urine Output – A sudden decrease in the amount of urine the body passes indicates an issue with your kidneys, which could eventually lead to kidney failure.
5. Nausea and Vomiting – Protein in the bloodstream changes the blood composition, and the imbalance leads to a range of symptoms, including nausea and vomiting.
6. Mental Confusion and Coma – An impaired mental function may also occur in extreme cases of rhabdomyolysis, presenting as confusion, disorientation, and decreased alertness.
7. Localized Pain and Numbness – When the muscle has become so damaged that pressure begins to build up, a severe condition known as compartment syndrome can occur due to restricted blood flow, causing reduced movement, pain, and loss of feeling in the affected body part.
8. Shortness of Breath – Fluid build-up in the lungs causes shortness of breath, and when combined with muscle weakness, can cause heart complications, leading to changes in heart rhythm and even cardiac arrest.
9. Unexplained Bleeding – Disseminated intravascular coagulation (DIC) occurs when changes in the blood cause blood clots, causes bleeding to begin for no apparent reason, and is a medical emergency.
10. Non-Specific Symptoms – People with this condition might report non-specific fever, chills, insomnia, and joint pain and confuse a diagnosis if they attributed it to a different cause.
Common CAUSES of Rhabdomyolysis in Cyclists
- High-intensity exercise: Initiating an exercise program at an excessively high level and progressing too rapidly.
- Severe dehydration and overheating: Excessive heat causes accelerated muscle breakdown, and if dehydrated, our kidneys can’t dispose of all the waste without plenty of fluids.
- Trauma: Blunt force and crush injuries, severe burns, and high-voltage electrical injuries can cause muscle fibers to disintegrate rapidly.
- Medications: Some medications can cause muscle breakdown, including antipsychotic, antidepressant, and antiviral drugs.
Quite significant for many as Statins have become the most widely prescribed drugs globally, this class of medications can also lead to rhabdomyolysis, especially in females, the elderly, and people who have diabetes or liver disease.
- Consumption of Black Licorice (and other Glycyrrhizin-containing substances): Can cause electrolyte imbalances, hypertension, and severe clinical conditions.[5]
- Heat Stroke: Prolonged exposure to high temperatures, which raise core body temperature above 40.5C, is a significant risk factor.
- Infection: Described in all types of infections, such as Epstein-Barr virus and Chicken Pox, and although research to support is not available at this time, Covid-19 may be a risk.
- Illegal drugs and alcohol: Heroin, LSD, cocaine, and excessive alcohol are toxic to the body and can cause muscles to deteriorate.
- Long periods of inactivity: People who fall, lose consciousness, and can’t get up for an extended time can develop the disease.
An avid cyclist and endurance athlete, upon noticing that his fitness level was declining and body weight was higher than desired, Graham began a 6 month training routine during which he committed to competing in his first triathlon in a while.
Graham aggressively increased the intensity and volume of training and maintained the trend right up to race day without tapering, fearing he may lose his edge. The August heat in Florida was brutal, as was the pace of the race, and he soon found himself struggling.
Graham ran through the warning signs and collapsed .1 mile from the finish. He awoke in an ambulance with IVs in each arm and no recollection of the events which put him there.
Graham was admitted to the hospital for 3 days to undergo rehydration and monitoring of LFT and CK levels after diagnosis of Rhabdomyolysis with associated renal complications.
Following discharge Graham limited his activity for ~1 week while receiving IV fluids. Attempts to resume light riding immediately forced his body back into a state of Rhabdomyolysis and to the hospital for testing and monitoring.
Graham’s status did not normalize for another month, after which, with the guidance of a coach knowledgeable in the signs and symptoms of Rhabdomyolysis, he guardedly resumed cycling.
Despite this, Graham suffered another setback when he failed to follow his coach’s advice and neglected to include rest days as advised.
“I had to take a break and pull back big time again,” notes Graham, “and now I force myself to take days that include zero exercise once or twice a week.
Rhabdo is a symptom of overtraining but the fear of losing fitness and body image issues are key for me.”
How is Rhabdomyolysis DIAGNOSED?
To diagnose rhabdomyolysis, your doctor will:
- Perform a thorough history and physical examination, including a neuromuscular exam focusing on the color, pulse, sensation, muscle power, and size of the extremities.
-
Take a blood sample:
The gold standard for laboratory diagnosis is the determination of plasma CK, with a concentration five times the upper limit of the normal range is the commonly used cutoff threshold. CK level is predictive of the likelihood of developing ARF.
Increased serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) can aid in the diagnosis, with elevation in 93% and 75% of cases, respectively - Take a urine sample: This test for the presence of myoglobin is not as sensitive as CK for diagnosis because concentrations normalize within 6-8 hours following muscle injury, resulting in false negatives, therefore only helpful if positive.
- Take a muscle biopsy: If a diagnosis is strongly suspected, a sample of muscle tissue will be lab tested and help find the underlying cause.
Conclusion
Thankfully, if aware of the warning signs and the knowledge of the importance of following a sensible training plan that emphasizes recovery, Rhabdomyolysis can be avoided.
In Part Two – Rhabdomyolysis: A Hidden Risk of Virtual Cycling we will explore the treatment, prevention, and specific implications to the virtual cyclist, including the story of one virtual cyclist’s near-fatal experience with Rhabdomyolysis.
In addition to emphasizing that the best cure for Rhabdomyolysis is prevention and the steps you can take to avoid this life-threatening disease.
Did You Know?
Were you aware that the severe health condition Rhabdomyolysis is prevalent in virtual cyclists and do you have any of the warning signs?
Bibliography
[1] “Freebie Rhabdomyolysis: A Public Health Concern. Spin Class ….” 28 Nov. 2016, https://www.amjmed.com/article/S0002-9343(16)31206-2/fulltext. Accessed 13 Apr. 2021.
[2] “Rhabdomyolysis – Mayo Clinic.” 2 Jan. 2014, https://www.mayoclinic.org/diseases-conditions/heat-exhaustion/multimedia/vid-20078262. Accessed 11 Apr. 2021.
[3] “Rhabdomyolysis – StatPearls – NCBI Bookshelf.” https://www.ncbi.nlm.nih.gov/books/NBK448168/. Accessed 11 Apr. 2021.
[4] “Update: Exertional Rhabdomyolysis, Active Component … – Health.mil.” 1 Apr. 2020, https://health.mil/News/Articles/2020/04/01/Exertional-Rhabdomyolysis-Active-Component-MSMR-2020. Accessed 11 Apr. 2021.
[5] “Low-dose liquorice ingestion resulting in severe hypokalaemic ….” 2 Jan. 2014, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4389170/. Accessed 12 Apr. 2021.
Accessed 12 Apr. 2021.
Semi-retired as owner and director of his private Orthopedic Physical Therapy practice after over 20 years, Chris is blessed with the freedom to pursue his passion for virtual cycling and writing. On a continual quest to give back to his bike for all the rewarding experiences and relationships it has provided him, he created a non-profit. Chris is committed to helping others with his bike through its work and the pages of his site.
In the summer of 2022, he rode 3,900 miles from San Francisco to New York to support the charity he founded, TheDIRTDadFund. His “Gain Cave” resides on the North Fork of Long Island, where he lives with his beautiful wife and is proud of his two independent children.
You will read him promoting his passion on the pages of Cycling Weekly, Cycling News, road.cc, Zwift Insider, Endurance.biz, and Bicycling. Chris is co-host of The Virtual Velo Podcast, too!
Great article Chris and some awesome insights on this . I definitely had no idea what this was before reading this. Keep it coming
Part Two coming tomorrow!
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