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Training is hard. It is supposed to be hard. Recruits are working to get ready to defend the country, and to do that they need to be in top shape. But, along with hard training comes bumps, bruises, muscle soreness and, on occasion, more serious issues.

One health risk that is receiving increased attention is exertional rhabdomyolysis. According to most definitions, exertional rhabdomyolysis is a condition or syndrome of skeletal muscle breakdown with release of myocyte contents into the circulation, which may arise from a variety of stresses that cause injury to muscle tissue.

That unclear definition is part of the problem with diagnosing the condition, according to Army Col. (Dr.) Francis O'Connor, medical director of the Consortium for Health and Military Performance in Bethesda, Md.

"The difficulty with exertional rhabdomyolysis is in part the definition; that's where it gets tricky," he says. "It is a product of muscle breaking down and getting into the blood and can be quite dangerous for some."

Regardless of the exact definition of the condition, it is estimated that 25 to 30 percent of cadets meet the criteria of exertional rhabdomyolysis, which includes a Creatine kinase (CK) level of five times baseline, excessive muscle soreness and weakness and, most tellingly, "Coca - Cola- colored" urine.

"According to a report, there were 400 cases diagnosed in 2012," says O'Connor. "It is probably a way underreported condition, when you consider the number of cadets and the number of cases we see."

Exertional rhabdomyolysis is most frequently associated with running activity and often seen along with heat stroke. However any extreme muscle overload activity may precipitate rhabdomyolysis, according to experts.

"Basic training is not the same as it was years ago. There is a reduced running load, rehab platoons to get cadets fit for basic if needed, hydration recommendations and proper attention to workload guidance," says O'Connor. "But there is still a risk due to a number of other factors ranging from environmental, viral, dehydration and others that can make even a seemingly fit individual susceptible."

Cases are not just growing among military ranks; in 2012 a study published in the Journal of Athletic Training showed that the incidence of exertional rhabdomyolysis in collegiate athletes appears to be increasing.

The issue gained increased media attention in 2011 when 12 University of Iowa football players were hospitalized with rhabdo. Just a few months earlier, 24 high school football players were treated for what many believed was rhabdomyolysis.

The JAT study cited that "Excesses in strength training and conditioning - workouts that are too novel, too much, too soon, or too intense (or a combination of these) - have a strong connection to exertional rhabdomyolysis. Introducing full-intensity workouts too quickly is especially high risk: 11 of the 21 deaths occurred during day 1 or day 2 workouts."

According to Dave Merson, a certified athletic trainer who is program director at Boston Sports Medicine, it doesn't matter whether the individual is military personnel, a college or pro athlete or a person at the gym looking to get fit for the beach; avoiding rhabdo often comes down to having the right guidance.

"Anyone looking to train intensely and successfully needs to have someone - be it an instructor, physical therapist, athletic trainer or personal trainer - leading them that can recognize and instruct the person when to go harder and when to pull back," Merson says. "Especially when undertaking daily physical activity such as basic training, or even ongoing fitness at a professional level, it is important to have a proper plan built around periodization to keep on track, safe and successful."

It is this training intensity along with increased use of supplements to help "energize" workouts - perhaps even prior to arriving at basic training - that may be one of the contributing factors to the increase in cases, according to O'Connor.

"It is very important that proper progression is followed. Going too fast, too quickly, such as seen with CrossFit and programs like P90X can increase the risks of exertional rhabdomyolysis," says O'Connor. "Additionally the use of energy drinks and pre-workout supplements with stimulants may be problematic as well. That's why it is really important for there to be someone trustworthy directing fitness endeavors both on and off base."

Regardless of fitness level and amount of exercise undertaken O'Connor stresses that trainees and recruits - especially if dehydrated, or working out in hot conditions - be aware of the symptoms of exertional rhabdomyolysis such as weakness and sore muscles that aren't recovering as quickly as others, and dark-colored urine, and report the symptoms immediately.

"Although it is rare, exertional rhabdomyolysis can kill you," he says. "Most who have the condition don't even need hospitalization. But a small segment of people never recover."

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