The summer months are a great time to get outside, play hard and break a sweat. And most troops are fit enough to push through a sweltering dog-day workout.
But danger lurks as the mercury soars and dew points rise, especially for young recruits, combat arms personnel and anyone stationed in brutally hot parts of the U.S.
Neglect your hydration and you may be at risk for muscle breakdown, kidney failure or even death, a condition known as exertional rhabdomyolysis, or “rhabdo.” Rhabdomyolysis occurs when overworked muscles break down, releasing a protein, myoglobin, into the bloodstream. This protein can overwhelm the kidneys, causing damage and, in a worst-case scenario, renal failure.
Last year, 378 active-duty troops experienced potentially life-threatening cases of rhabdo, according to a report from the Armed Forces Health Surveillance Center.
The number of cases is down since 2011 but remains 33 percent higher than in 2009, which should serve as a warning to anyone who PTs or leads PT in the summer months when rhabdo cases peak, according to AFHSC researchers.
“Medical providers should consider [rhabdo] … when service members, particularly recruits, present with muscular pain or swelling, limited range of motion or the excretion of dark urine after strenuous physical activity, particularly in hot, humid weather,” the report notes.
Broken down by service, the 378 rhabdo cases last year included 177 in the Army, 35 in the Navy, 50 in the Air Force, 155 in the Marine Corps and one in the Coast Guard.
No deaths occurred, but 168 of those service members were hospitalized.
“Whenever you work out, you have some muscle breakdown. It’s when you try to outdo someone else or you are not ready for repetitive or challenging exercise that you can do severe damage to the muscle fibers,” said Dr. Chris Holstege, director of the Medical Toxicology Division at the University of Virginia Medical School. Holstege is currently treating three civilian cases of rhabdo.
From 2009 to 2013, cases peaked from June to August and were at their highest at the Marine Corps recruit depots in San Diego and Parris Island, S.C.; Lackland Air Force Base, Texas; Fort Benning, Ga.; and at large permanent stations including Fort Bragg, N.C., Camp Pendleton, Calif., and Fort Hood, Texas.
Service members most at risk are recruit trainees under age 20, those of Asian, Pacific Islander or black non-Hispanic descent, those training in the combat arms, particularly in the Army and Marine Corps, and those whose homes of record are in the northeast U.S., according to the study.
The drop in military cases since 2011 is a promising sign that commanders, doctors and troops recognize the dangers of overdoing physical fitness in the heat, Holstege said.
But more can be done to prevent it, he added.
Gradually increasing training and proper hydration, by drinking water and replenishing electrolytes with simple fixes such as powdered or premade Gatorade are key, Holstege said.
Some medications such as statins, antipsychotic drugs and selective serotonin reuptake inhibitors can raise the risk of developing rhabdo, as can stimulants such as Adderall or dietary supplements containing stimulants.
Some individuals also may have a genetic susceptibility to rhabdo and other heat-related illnesses but may not find out about their propensity until after they’ve developed the condition, Holstege added.
Rhabdo entered the lexicon of familiar exercise-related injuries with the rise in popularity of CrossFit, the challenging workout regimen that pushes one’s body to its limits. As far back as 2005, physiologists warned of the potential negative health impact of Crossfit and other extreme workouts on the body.
Holstege said he usually sees patients get into trouble when they are doing these and other similar workouts in competition with others.
“The majority of the cases I’ve seen really seem to occur when people are trying to outdo one another. Fortunately, the kidneys are really forgiving,” Holstege said.
Holstege recommends that all athletes eat a balanced diet, hydrate adequately and avoid dietary supplements, which he says often contain unknown ingredients or additives such as stimulants or substances that negatively impact how the body reacts to increases in temperature or exertion.
Oddly, rhabdo also can occur when a body is completely immobile, so Holstege also recommends against mixing sedatives and alcohol or consuming too much alcohol. A recent rhabdo patient at the University of Virginia Medical Center was a fraternity pledge who passed out for a prolonged period of time, he said.
Mainly, though, rhabdo cases peak during the hot summer months when people push themselves too hard, he said.
But exercise smart and you should be fine, he added.
“The vast majority recognize their limitations and drink plenty of fluids. It’s those people who have been sedentary all winter and, now that it’s spring, go out and push themselves to run six-and-a-half-minute miles who are at risk. Slowly increase the weight, slowly increase the length of your workout or your run, and you can avoid damage.”