Exertional, or exercise-induced rhabdomyolysis (ER) is a rare but sometimes catastrophic condition in which muscle fibers break down in response to exertion and release their breakdown products into the circulation. Commonly referred to as “rhabdo” among health professionals, this condition was first observed and studied during the bombing of London in World War ll. People trapped in the rubble sustained severe crush injuries and often died of kidney failure. The situation in which it was discovered earned it the description of “crush syndrome”.
Today, most cases of ER are observed in people whose muscles have been severely damaged by intense exercise. In any given year a busy emergency room will treat an average of eight cases of ER. Moderate cases can be triggered by rigorous physical events—such as triathlons, obstacle courses and basic military training—or by any other strenuous exercise sessions that the participant is not well prepared for, such as a heavy weight-lifting session.
In moderate cases participants have a high enough level of the chemical myoglobin in their blood to cause painful symptoms but not enough to cause kidney failure. Severe cases of ER are potentially life threatening. Personal trainers need to be particularly aware of the danger of ER, as it is within their power to inadvertently encourage their clients to push past a safe level of exercise and into the range of overexertion. There have been numerous lawsuits regarding trainers encouraging their clients to disregard signals that their body is giving them. The popular form of cross training known as Crossfit seems to generate a particularly large number of these lawsuits. That said, it is important to remember that it is a trainee’s responsibility to know when enough is enough, and that they need to cool off and take a break from intense exercise. Typically, the most common signs that you are crossing over into overexertion are an accelerated heart rate, shaking or a burning sensation in muscles, or symptoms of low blood sugar. Once exertional rhabdomyolysis has taken effect there are four signs that signal its occurrence:
Muscular Symptoms and Signs- Muscle pain, weakness, tenderness, stiffness and contractures are the most common muscular symptoms related to ER. A burning sensation or inability to move limbs in a certain range of motion are also common.
Myoglobinuria (Leaking of Myoglobin Into the Urine)- When muscles fibers are destroyed by intense exercise or external damage, myoglobin and other cell components flood into the blood stream and can disrupt organ functioning, mainly the kidneys. There is a distinct brownish color to the urine during ER.
Laboratory Features- Between 2 and 12 hours after the muscle damage, creatine phosphate levels will rise dramatically.
Constitutional Symptoms. These symptoms include fever, tachycardia, nausea and vomiting. Confusion, panic, loss of consciousness and low urine output can also be characteristics. ER complications can include acute kidney failure and death. Life-threatening complications other than renal failure include excessively high levels of potassium in the blood and problems with blood clotting.