Overexertion Can Cause Serious Harm

Two days after an intense training session, an apparently healthy client experiences such extreme muscle soreness that she seeks emergency care. Her urine is very dark. At the hospital, she is diagnosed with exertional rhabdomyolysis. What does this mean? And could her trainer have prevented it?

Rhabdomyolysis is a medical condition that results from direct muscle injury or an altered metabolic relationship between energy production and energy consumption in muscle. Causes include drug toxicity, heat stress, muscle trauma and physical exertion.

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. In any given year a busy emergency room will treat seven to 10 cases of ER. Moderate cases can be triggered by endurance events—such as triathlons, marathons and basic military training—or by other exercise for which a participant is not well adapted (for example, excessive resistance training). In moderate cases participants have unusually high myoglobin levels in their blood but not enough muscle damage to cause renal—kidney—failure or insufficiency. (Myoglobin is a protein, similar to hemoglobin, that binds oxygen in the muscle.) Severe cases of ER can be life threatening.

Personal trainers should clearly be familiar with the symptoms of ER and know how to prevent and respond to occurrences. Described below are ER’s central features and important preventive measures. The sidebar summarizes two case studies in which personal trainers were directly implicated.

Primary Features of Rhabdomyolysis

Rhabdomyolysis has four primary features:

Muscular Symptoms and Signs. The most common symptoms include muscle pain, weakness, tenderness, stiffness and occasionally contractures.

Myoglobinuria (Filtration of Myoglobin Into the Urine). ER especially damages red (type 2) muscle fibers. After muscle injury and necrosis (cell death), myoglobin is released, along with other cellular contents. When released in large amounts, myoglobin is filtered into the urine. A change in urine color is usually the first sign of myoglobinuria. Dark urine, typically brown in color, is often the first clueto rhabdomyolysis.

Laboratory Features. The hallmark of muscle damage is elevated creatine phosphokinase, or creatine kinase (CK). Normal CK levels are between 20 and 200 units per liter (U/L), perhaps slightly lower in females. CK levels begin to rise 2 to 12 hours after muscle injury or extreme muscular exertion and may rise as high as 20,000-300,000 U/L.

Constitutional Symptoms. These symptoms include generalized malaise, fever, tachycardia, nausea and vomiting. Altered mental status (e.g., confusion) and low urine output can also be characteristics. ER complications can include acute renal (kidney) failure and, in some cases, death. Life-threatening complications other than renal failure include hyperkalemia (higher-than-normal levels of potassium in the blood) and disseminated intravascular coagulation ( a blood clotting condition). How often cases result in these complications largely depends on the level of rhabdomyolysis and the speed at which the persons affected seek and receive medical help. The medical literature reports that up to 40 percent of patients may end up with renal failure; however, one report on 35 male patients with ER seen in a Brooklyn, New York, emergency center (Sinert 1994) did not observe any renal failure - likely thanks to rapid, aggressive medical therapy.

Preventive Measures for Personal Trainers

What do personal trainers need to do to lessen their clients’ risk of experiencing the symptoms and complications of ER?

1. Understand the Causes and Symptoms of ER.

2. Be Prepared for Expedient Client Management. For most personal trainers this means immediately referring an affected client to qualified medical care (e.g., by a competent physician). Medical treatment can include hydration, diuretics, electrolyte correction, dialysis and other supportive therapy.

3. Know the Common Triggers. In nearly all cases of ER, the exercise stimulus is an "unusual exercise load" or an abrupt transition to a much greater exercise load. Dramatic increases in exertional load (duration and/or intensity) or exposure to unaccustomed heat stress can increase risk. Monitor perceived effort in the early stages of training and observe for signs of excessive fatigue or overexertion. An excessive level of delayed-onset muscle soreness is always a reasonable indication that training loads experienced a day or two earlier were excessive.

4. Recognize That Some Individuals Are More Susceptible to ER Than Others. More susceptible clients require closer supervision, especially in the early stages of resistance training. This group includes clients with previous histories of ER or ER-like symptoms, clients with low initial levels of fitness, older individuals and clients with muscle disease (e.g., muscular dystrophy). However, most cases of ER involve apparently healthy and reasonably fit individuals. Note also that performance-enhancing drugs (e.g., anabolic steroids) have been implicated in ER (Sandhu 2002). And other drugs - among them statin drugs, used to lower blood cholesterol - can increase the likelihood that ER symptoms will occur during a bout of resistance exercise involving eccentric contractions.

Knowledge Is Key

ER is a relatively rare clinical phenomenon. However, in the course of a personal training career, the chances of observing one or more cases of ER or at least some ER symptoms are quite high—perhaps 30 to 50 percent. It is therefore crucial for personal trainers to understand the condition. Clearly, the line between a systematic and progressive approach to exercise training and a method that imposes excessive repetitive force or intensity can sometimes be a fine one. Trainers need to be cautious about pushing clients to unnecessary limits of intensity, especially in resistance and anaerobic-based training programs.

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Ralph La Forge, MS

IDEA Author/Presenter
Ralph La Forge, MS, is a physiologist and board-certified clinical lipid specialist. He is the ma... more less
January 2004

© 2004 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.

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