The NCAA News - News and Features

The NCAA News -- Sports Sciences Newsletter -- October 26, 1998

Exertional rhabdomyolysis

BY PRISCILLA M. CLARKSON
University of Massachusetts

In the fall of 1997, three wrestlers died while performing intense exercise and practicing dehydration procedures. The autopsy report for one of the wrestlers cited the cause of death as rhabdomyolysis, which is defined as a degeneration of muscle cells and is characterized by a group of symptoms including myalgia, muscle tenderness, weakness, swelling, brown urine (called myoglobinuria) and increased levels of muscle proteins in the blood. One of the proteins released from damaged muscle cells is myoglobin. In certain situations, myoglobin can precipitate in the kidneys and cause renal failure and even death.

I was involved with the evaluation of one incident of rhabdomyolysis that took place at a police training academy in Massachusetts. Over the course of the first day of training, 50 police cadets performed numerous calisthenics, including sit-ups, push-ups and jogging. It was a warm day, and there was some question as to whether the cadets had easy access to water. At 4 p.m. that day, a 25-year-old cadet collapsed during a training run and was rushed to a local hospital, diagnosed with acute renal failure and put on kidney dialysis. Forty-one days later he died. Eleven other cadets were hospitalized, two of whom were placed on dialysis, and all survived. I served on the committee to determine what happened and to make recommendations leading to changes in police training practices. Now unaccustomed intense exercise is not to be performed without proper prior training and conditioning and water is to be readily available during training.

There are many instances in medical literature of rhabdomyolysis induced by intense, unaccustomed exercise. Recently, however, I have been concerned with the number of phone calls I have received from parents, coaches, representatives of athletic programs and legal advisors describing the occurrence of rhabdomyolysis in athletes and requesting information.

Consequences of rhabdomyolysis

Performance of intense unaccustomed exercise causes damage to the contractile protein filaments in muscles. If this damage is not too severe, the result will be delayed onset muscle soreness and stiffness which is usually accompanied by some loss in strength and range of motion. The soreness develops about six to 10 hours after exercise and peaks between 24 to 48 hours after. When the damage is more extensive, the protein myoglobin is released from the damaged fibers into the blood. Myoglobin reaches a threshold amount in the blood and then "spills over" into the urine, discoloring it in a range from a light "iced-tea" to a "Coca-Cola" color. With dehydration and/or heat stress, myoglobin can precipitate in the kidneys and cause renal failure, a serious condition that can result in death.

Often accompanying rhabdomyolysis is an elevation of potassium in the blood. Potassium is released into the blood from damaged muscle cells. If there is a problem with kidney function, the kidney cannot excrete it causing blood potassium to reach dangerous levels. Excessive potassium interferes with heart function and leads to heart block and cardiac arrest.

Incidences of rhabdomyolysis

Cases of rhabdomyolysis are not new. One of the first associations between acute renal failure and darkly colored urine was noted in London during World War II bombings that left patients suffering from crush injuries to muscles. In the late 1960s and 1970s, several cases appeared during military training. For example, eight young men who were in a training program for Naval aviation officer candidates developed grossly discolored urine and severe muscle pain. They participated in novel strenuous exercise within 38 hours of when the dark urine was noted. The men performed repetitive push-ups along with other exercises (leg-lifts or straddle-hops). These calisthenics often were assigned by the drill instructors for minor violations of cadet rules. Restoration of functional capacity took several weeks.

In 1974, 40 Marine Corps recruits were hospitalized following several days of excessive upper-body calisthenics. Many reported dark urine and all were diagnosed with exertional rhabdomyolysis. Thirty-three subjects of 586 recruits in the first two weeks of training at an Officers Candidate School exhibited brown urine and other symptoms of rhabdomyolysis. Although two to three weeks were necessary for recovery of muscle function for most individuals, after six weeks, eight still showed muscle weakness, and after three months, one subject was still weak.

The cases cited above for military recruits were self-resolving. However, during the period from 1958 to 1965, renal failure was documented in 10 Army recruits, including two who died, who had participated in the first sessions of basic training. Autopsies revealed extensive muscle damage and death of muscle cells. Similar to the deceased wrestlers, all of the recruits had experienced heat stroke or heat stress, and their state of hydration was compromised. Thus, heat stress appears to exacerbate rhabdomyolysis, making it even more dangerous.

Incidences of rhabdomyolysis also have occurred during athletic training. For example, three young men who, after participating in the first session of body-building exercises, complained of muscle pain and dark urine. All had regularly engaged in sport activity (but not these body-building exercises) prior to the body-building session. Other cases have been reported after first sessions of weightlifting training or other forms of novel unaccustomed recreational exercises. These situations were either self-resolving or required kidney dialysis, and all involved survived.

In each of these reports, strenuous repetitive calisthenic-type exercises (push-ups, pull-ups, squats, weightlifting) performed during the first few days of training produced rhabdomyolysis. The excessive repetitions of the same exercise would classify them as novel to most individuals. Because of the principle of exercise specificity, few individuals would be conditioned for this type of exercise.

Why are some individuals more susceptible?

Although the data on exertional rhabdomyolysis are alarming, it should be noted that only a relatively small percentage of severe cases have been recorded. For example, of the 16,506 candidates who took a firefighter fitness test in New York during 1988 and 1989, 32 were hospitalized with renal failure. Thus, some individuals appear to be more susceptible. Because only novel strenuous exercise will likely produce muscle damage, the specificity of exercise training is important. If an individual is trained in one activity (i.e., endurance running), this may provide the person with little or no "protection" if they perform 100 push-ups, or even repetitive squat-jumps and leapfrogs.

Some individuals may have a hereditary subclinical muscle enzyme or other defect. Under normal exercise stress, this condition would go unnoticed. However, performance of very strenuous, repetitive, unaccustomed exercise will exacerbate muscle damage. Also, in a competitive event, the zeal to win or shame of quitting may allow some individuals to go beyond a tolerable level of muscle injury.

Other factors that may be involved are the presence of cold or flu-like symptoms, abrupt changes in diet or use of ergogenic aids. A common feature in those cases where renal failure has occurred is that the ambient temperatures were generally high and many of the individuals appeared to suffer from heat stress, characterized by either profuse sweating or heat stroke. Some individuals may be more susceptible to heat stress. Susceptibility is influenced by the state of dehydration as well as the state of acclimatization. Also, there may be a subclinical latent muscle disorder that would predispose certain individuals to heat stress and rhabdomyolysis.

Summary and recommendations

Rhabdomyolysis is brought on by the performance of unaccustomed, excessive, repetitive exercises such as push-ups, squat-jumps and leapfrogs. It also can occur after strenuous recreational activities such as marathon running and hiking, or performance of excessive strenuous exercise during the first days of a new training program. Although mild cases of rhabdomyolysis do not require hospitalization and individuals recover within one week, the condition can be severe in certain individuals. Added heat stress can produce acute renal failure, which, in rare instances, can result in death. Some individuals may have a latent, subclinical muscle disorder that predisposes them to the most negative consequences of rhabdomyolysis.

Coaches should never begin a training season using repetitive or strenuous, unaccustomed exercises. All exercise training should begin with mild intensity exercise, which is gradually increased to an appropriate level. This practice will ensure safety. Moreover, preventing even moderate muscle soreness will benefit training because working with sore muscles (which also are weaker) will compromise the quality of the practice sessions.

Other factors that should be considered for exercise in a warm or hot environment are acclimatization, diet and fluid intake. Athletes should be advised not to try any new diet manipulation for the first time prior to a strenuous competitive event or practice, nor should they use drugs which can exacerbate muscle damage. Because dehydration is implicated in rhabdomyolysis, adequate fluid should be available and ingested before and during exercise. During strenuous exercise in the heat, precautions such as adequate fluid intake and acclimatization are critical.

Rhabdomyolysis and its serious consequences can be avoided by maintaining adequate hydration, avoiding heat stress, not performing strenuous repetitive exercise for which a person is not trained and increasing exercise intensity in a gradual manner. These safeguards will prevent subsequent muscle pain and optimize performance, but more importantly, they may save a life.

I am interested in starting a directory of rhabdomyolysis cases involving athletes. If you are aware of documented cases of rhabdomyolysis, please contact me via e-mail.

Priscilla M. Clarkson is a member of the NCAA Committee on Competitive Safeguards and Medical Aspects of Sports and associate dean of the School of Public Health and Health Sciences at the University of Massachusetts. She may be contacted at 413/545-6069; e-mail: clarkson@excsci.umass.edu.