By Daniel G. Graetzer, Ph.D. and Daniel J. Borowick, M.S., C.S.C.S.
Faculty Member, School of Health Sciences and Sports and Health Sciences Alumnus
Exercise-induced rhabdomyolysis (also known as rhabdo) is a potentially life-threatening syndrome that is especially prevalent in tactical athletes and sports athletes. Tactical athletes include first responders such as law enforcement, firefighters, servicemembers and other professionals who rely on their bodies to protect the lives of other people.
What Causes Rhabdomyolysis?
Rhabdomyolysis is caused by the excessive breakdown of skeletal muscle fibers, leading to leakage of muscle proteins and electrolytes into the body’s blood. Dehydration – especially during physical exertion in hot and humid environments – impairs the effective removal of these “dead” muscle particles in the urine.
Dehydration does not cause rhabdomyolysis by itself, but it often makes rhabdomyolysis much more serious. Rhabdomyolysis has the potential to progress into compartment syndrome or renal failure, so it requires prompt diagnosis and treatment.
Rhabdomyolysis has multiple causes. For instance, the causes of rhabdomyolysis include:
- Direct or indirect trauma (often a crush-related injury from falling or a vehicle accident)
- Excessive physical exertion
- Muscle compression caused by prolonged immobilization
- Heat exposure, especially if someone has ingested too much alcohol and certain legal/illegal drugs
- Electrical shock
- Lightning strikes
- Third-degree burns
- Snake/insect bite venom
Sometimes, this disease appears as a “triad” of symptoms. Classic “rhabdomyolysis triad” symptoms are:
- Muscle pain in the shoulders, thighs or lower back (note: approximately 50% of persons have no muscle-related symptoms)
- Muscle weakness or trouble moving the arms and legs
- Dark red or brown urine or decreased urination
Rhabdomyolysis in Servicemembers
According to an April 2020 article published on Health.mil., there were 501 cases of exertional rhabdomyolysis or 37.8 cases per 100,000 military servicemembers. These cases were most prevalent in military bases during basic combat/recruit training or within large ground combat units of the U.S. Army and Marine Corps.
Why did so many servicemembers experience this medical problem? Rhabdomyolysis is common when servicemembers begin a quick and sudden escalation of physical activity – typical in basic training – without undergoing sufficient physical conditioning in advance. This syndrome also appears when servicemembers are in hot, humid environments to which they are not properly acclimated.
Compartment Syndrome Can Follow Rhabdomyolysis
If someone retains excessive fluid, compartment syndrome might occur after severe rhabdomyolysis. A group of muscles bound together within a thin, fibrous sheath is called a compartment.
Injury to the muscles inside the sheath may cause swelling-induced pressure to occur inside that compartment; this pressure then rises rapidly due to muscle sheaths being very resistant to stretching. As a result, the high pressure prevents blood from entering the sheath and blood-deprived muscles inside the sheath begin to die.
Rhabdomyolysis following skeletal muscle injuries can rapidly lead to a swelling of cells that squeezes out their contents – electrolytes, myoglobin and creatinine kinase – into the blood. Elevated levels of these cell contents in the blood are used to diagnose compartment syndrome.
The level of creatinine kinase in the blood, which is too large to leak through a cell’s wall unless the muscle cell lining is ruptured, typically peaks in one to three days before starting to decrease. If the rhabdomyolysis is extensive, compartment syndrome and muscular injuries may result.
Also, the release of myoglobin and uric acid can lead to renal injury and in some cases even renal failure. Currently, the most effective treatments focus on the protecting the kidneys using hydration and diuresis.
Excessive Exercise, Especially in Hot Environments, Can Induce Rhabdomyolysis and Compartment Syndrome
Excessive exercise using eccentric contractions (the elongation of skeletal muscles while under tension) in the heat is known to quickly induce rhabdomyolysis and compartment syndrome. If someone has a nutritional deficiency causing an imbalance of electrolytes, that can worsen the patient’s condition.
Normally, the human body reduces the buildup of metabolic heat during exercise by blood flow adjustments and sweat gland secretion. Flushed, red skin indicates that peripheral blood vessels have dilated, carrying blood and internal heat to the body surface for cooling.
Once this metabolic heat is carried to the peripheral blood vessels by the bloodstream, its dissipation is accomplished mainly by the evaporation of sweat. It is important to remember that sweating by itself does not cool the body – only the evaporation of sweat does.
Contrary to what many people would like to believe, nearly all of the weight loss incurred during exercise is due to water loss and not the loss of fat weight. A caloric expenditure of about 3,500 calories is required to burn one pound of fat from the body.
The caloric cost of running a 26.2-mile marathon is only about 2,600 calories and a majority of these calories come from carbohydrates, not fat. The total fat loss from running a marathon is less than one-fourth of a pound, and the remaining weight loss (often 5-10 pounds over 26.2 miles) comes nearly entirely from water loss through sweat.
The rate of sweat evaporation is highly dependent on the relative humidity (the percentage of moisture saturation) of the ambient air. Large quantities of sweat may roll off the skin during exercise in a high-humidity environment, but if that sweat is not effectively evaporated, dehydration and heat illness may result. On the positive side, even a minimal amount of wind (or fan-driven air circulation when someone exercises inside) elevates the percentage of sweat that evaporates.
Rhabdomyolysis and Compartment Syndrome Require Immediate Medical Attention
Both rhabdomyolysis and compartment syndrome require immediate medical attention. Any delay in treatment can potentially lead to kidney damage, heart damage and permanent disability. Most patients recover well after treatment, but they may have lingering muscle weakness for a few weeks.
Acute kidney injury occurs in up to 50% of rhabdomyolysis cases with some patients needing kidney dialysis for an extended period of time. Compartment syndrome requires prompt surgical treatment to prevent permanent muscle damage and high levels of myoglobin, electrolytes, and uric acid in the blood, resulting in worsening renal function, potential heart dysrhythmias, and in rare cases even death. If you notice that your urine is a dark tea color one to three days after an intense workout, please visit a healthcare provider immediately.
About the Authors
Daniel G. Graetzer, Ph.D., received his B.S. from Colorado State University/Fort Collins, MA from the University of North Carolina/Chapel Hill, and Ph.D. from the University of Utah/Salt Lake City and has been a faculty member in the School of Health Sciences, Department of Sports and Health Sciences, since 2015. As a regular columnist in encyclopedias and popular magazines, Dr. Graetzer greatly enjoys helping bridge communication gaps between recent breakthroughs in practical application of developing scientific theories and societal well-being.
Daniel J. Borowick graduated from American Military University in 2020 with a master of science in Sports and Health Sciences. His capstone project, “Program Design Based on Genetically-Determined Type I and Type II Fiber Typing In Order to Achieve Optimal Athletic Performance,” was written under the guidance of Professor Daniel Graetzer and is available online. Daniel is currently a Certified Strength and Conditioning Specialist (CSCS®) with certification from the National Strength and Conditioning Association (NSCA®). Currently, Daniel is a private contractor as a C.S.C.S. with the United States Army’s 1st Armored Division SustBrigade’s H2F Program and a former DEA Special Agent and Physical Task Assessment Administrator. CSCS and NCSA are registered trademarks of the National Strength and Conditioning Association.