Delayed Onset Muscle Soreness (DOMS) and Exertional Rhabdomyolysis

All strenuous exercise results in some degree of muscle fiber breakdown. The extent of muscle fiber breakdown is dependent upon several factors, all of which are under the control of the person in charge (e.g., the exerciser himself/herself, or their coach, teacher, drill instructor or personal fitness trainer). I have categorized the damage thusly along a continuum:

• Normal and beneficial muscle fiber breakdown resulting in an array of physical and metabolic circumstances which cause little or mild muscle soreness
• Supernormal muscle fiber breakdown resulting in an array of physical and metabolic circumstances which cause severe muscle soreness that can hamper normal movement, activity and flexibility
• Major (severe) muscle damage resulting in an array of physical and metabolic circumstances which threaten the long-term well-being or life of the individual.

The first two syndromes are widely referred to as “delayed onset muscle soreness” (DOMS), and most people who have exercised strenuously have experienced it to one degree or another. If the continuum were numbered in a fashion similar to the Borg scale of perceived exertion, the first may be rated between 6 – 12, the second between 13 – 17, and the third, referred to by the medical community as “exertional rhabdomyolysis,” between 18 – 20. It is the third degree of the continuum which concerns me greatly, as the incidence of this syndrome appears to either be increasing or more frequently reported. It can result in kidney failure and death. There are instances in which personal fitness trainers were found culpable.

Exertional rhabdomyolysis is characterized by hypokalemia, intravascular coagulation, hyperuricemia, myoglobinuria, myalgia, and lactic acidosis. Exertional rhabdomyolysis may occur after an individual performs unaccustomed, exhaustive exercise in the heat and/or may be exacerbated when the individual is dehydrated. Some people appear more susceptible to exertional rhabdomyolysis than others. Heat stress and dehydration appear to exacerbate rhabdomyolysis, making it even more dangerous in an exercise setting, particularly among new detrained clients. Clearly, owing to the markers which describe the condition, exertional rhabdomyolysis can only be diagnosed by a physician with a sophisticated laboratory at his/her disposal.

Exertional rhabdomyolysis develops from both exercise and nonexercise risk factors. The amount of cellular damage may be affected by a subject's 1) fitness level. 2) the intensity of exercise, 3) the duration of exercise, and 4) the type of exercise.

• Fitness level. Muscle tissue adapts to exercise, allowing the tissue to perform more work, resist damage, and repair at a faster rate. Thus, an experienced athlete would be less likely to develop exertional rhabdomyolysis, while a new client in a detrained state would be more likely to show signs of exertional rhabdomyolysis.
• Intensity and duration. Studies show that increasing the intensity of an activity (eg, lifting heavier weight, pedaling faster) results in higher creatine kinase levels (widely regarded as the most important marker of exertional rhabdomyolysis) when compared with increasing the duration (eg, more repetitions with less weight, longer bicycling with slower pedaling).
• Type of exercise. Different amounts of cellular destruction occur between concentric exercise and eccentric exercise. Eccentric activities cause more destruction, resulting in higher levels of intracellular contents in the bloodstream.

Minimizing Risk

The best treatment for rhabdomyolysis is prevention. Participants in exercise programs should increase the intensity of their exercise programs at a pace that will allow muscle tissue time to adapt. Limiting or avoiding exercise during high temperature and humidity conditions, and limiting exercise during times of illness are also advised. Clients who have predisposing risk factors, such as metabolic myopathies, sickle cell trait, or certain viral infections, should be instructed by their physician to observe precautions when exercising. In such instances, if a personal trainer is involved, his/her job requires that consultation with the client’s physician is carried out.

Personal fitness trainers should never begin training a new client 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.
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.

In summary, exertional 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.