Grunt: The Curious Science of Humans at War

by Mary Roach

  “Do you take it off because it’s too hot?” I’m like a fly buzzing around his head. A little yapping dog at his ankles.

  “I take it off because it makes sense.”

  Dan steps in to lighten the tone. “Mary, we’re walking up and down mountains with a hundred pounds on our backs, fighting guys in sandals and man-dresses. The Army’s answer to a lot of things is to give you more equipment, more stuff, most of which takes batteries, and there’s only so much you can carry.”

  The Army’s other answer, one they have flirted with for over a decade now, is a wearable hydraulic exoskeleton to help with heavy loads. Lockheed Martin posted a video of its entry, the HULC (Human Universal Load Carrier), on YouTube. Soldiers are shown bounding across gullies and taking cover behind boulders while wearing articulated metal braces on the outsides of their legs, as though the Army had taken to conscripting 1950s polio victims. The HULC was tested at Natick in 2010, on a “prolonged march” with an 87-pound load. One of the comments posted for the YouTube video comes from a participant in that test: “Everyone was pretty much done at forty-five minutes due to shin splints. ” Others questioned whether fighters could move quickly under fire or even pick themselves up if they fell. Patrick Tucker, the technology editor for the website Defense One, tripped over the battery life: five hours, provided you’re moving slowly (2.5 mph) and on level terrain. He doubted HULC’s usefulness in places without a steady power supply—“like, basically any place where soldiers might, you know, have to fight.”

  “Do you want to know why my friend got killed?” says Josh. “Somebody probably heard him going into the building, because he couldn’t be quiet enough, because he’s carrying too much shit in the first place. There’s all kinds of restrictions that risk-averse people are making. They have good intentions but they have bad effects.”

  Dianna points to my tape recorder. “You can probably turn that off.” Heat isn’t going to be a topic, just a mood.

  DRIVING BACK from lunch, Josh and Dan sit in the back, planning their workout. I hear Dan say, “one hundred snatches,” which hits my ear like a Dr. Seuss title. Up in front, Dianna and I talk science. I tell her about my recent visit to Natick Labs. They have a manikin that sweats! And “water-needs prediction equations”! You plug in the weather report and the fighters’ loads and activity levels, and it tells you how much water you’re going to need to haul to the battlefield. How excellent is that, I want to say, but I know Josh is listening.

  I understand his scorn. I understand there’s always a factor left out of the equation, something unknowable to someone who’s not out there, inside the madness. I know every mission has unique requirements and risks. I know why there are derogatory names for people who sit in air-conditioned offices making rules for people out humping artillery across an open courtyard at noon in Afghanistan. Though at the moment, I can’t remember what those names are.

  “Chairborne Ranger?” offers Dan. “Pogue?”

  “Scientist,” says Josh. Dianna taps the steering wheel with one thumb. She glances in the rearview mirror. “I love you, son.”

  Josh stares out the window. “I love you too, Ma. No shame.”

  A few words in defense of military scientists. I agree that squad leaders are in the best position to know what and how much their men and women need to bring on a given mission. But you want those squad leaders to be armed with knowledge, and not all knowledge comes from experience. Sometimes it comes from a pogue at USUHS who’s been investigating the specific and potentially deadly consequences of a bodybuilding supplement. Or an army physiologist who puts men adrift in life rafts off the dock at a Florida air base and discovers that wetting your uniform cools you enough to conserve 74 percent more of your body fluids per hour. Or the Navy researcher who comes up with a way to speed the recovery time from travelers’ diarrhea. These things matter when it’s 115 degrees and you’re trying to keep your troops from dehydrating to the point of collapse. There’s no glory in the work. No one wins a medal. And maybe someone should.

  ___________

  * Kuno and his team spent a great deal of time exploring the differences between thermal and emotional sweating, the latter wetting the palms and soles and the former, everything but. One researcher excised a patch of leg skin and grafted it to his palm. Would the patch henceforth, unlike normal leg real estate, sweat when the man was nervous ? (Yes.) Would it remain dry in emotionally trying circumstances, such as when colleagues tittered over the sudden and suggestive appearance of hair on one’s palms? (No.) The emotional sweat work conferred a corollary talent for lab-based sadism. The researchers invented and delivered terrible news to their subjects. They tasked them with oral arithmetic problems. They threatened to administer painful shocks, provoking “the uneasiness of expecting pain.” Kuno was the Stanley Milgram of perspiration.

  † The human head sweats like a mother. As the cradle of the brain, it’s served by a lot of blood vessels, and those vessels, unlike the vessels of the body’s other extremities, don’t constrict. Thus head wounds bleed readily and faces flush and sweat. But it’s misleading to say, as one so often hears, that people lose 90 percent of their body heat via their head. “My father-in-law, when he sees me go out in winter with no hat, always tells me that,” says military research physiologist Sam Cheuvront. “I say, ‘If that’s true then I should be able to put on a tassel cap and go outside naked and retain 90 percent of my body heat.’” When in fact, he’d be losing heat through his exposed body parts. Though gaining my affection.

  ‡ Charms used to be part of ground rations, too. They were removed partly because of a persistent belief that they brought bad luck. No one at the Natick Labs Combat Feeding Directorate knows the origins of the unlucky-Charms superstition. I like this guess best, from the gun-enthusiast website AR15.com: “Because the plastic wrapper sticks . . . and results in you getting drilled in the brainpan because you were picking at a piece of candy and not paying attention.”

  Leaky SEALs

  Diarrhea as a threat to national security

  SHOULD YOU ONE DAY travel to the overlooked desert nation of Djibouti, you will see from the window, as you land, what appears to be a large construction site adjacent to the airport. In fact, it’s a US military base, Camp Lemonnier: 3,500 people who live and work in retrofitted shipping containers, some stacked, some side by side, a Tetris of unadorned rectangular boxes. Other than the shrubs that grow in the drip from the air-conditioning units, there is no landscaping. Interior décor takes the form of emergency instruction placards (“Stop and listen to the Giant Voice . . .”) and framed chain-of-command portraits. In three days on base, I’ve seen a single item that one might class as luxury: one indulgent, cushy, costly item shipped here for no other reason than to add a little comfort to a soldier or sailor or airman’s life. Captain Mark Riddle requisitions Charmin Ultra Soft for the container that belongs to Naval Medical Research Unit 3. The sign on the door explains it: Diarrhea Clinical Trial.

  The word alone makes people want to laugh: diarrhea. Riddle doesn’t fight this. On the contrary. He recruits study subjects through GOT DIARRHEA? signs on the backs of restroom stall doors. One of the photographs on the Stool Grading Visual Aid he created for participants in the current study comes from a Campbell’s Chunky soup ad. (“Look closely,” he’ll confide, “there’s a spoon sticking out.”) Nevertheless, for reasons you will come to understand, Riddle takes diarrhea very seriously. As he has put it, intending nothing funny, “I live and breathe this stuff.” I have heard him use the word sacred to describe a collection of frozen stool samples. Riddle would like military brass to take it seriously, too.

  In past centuries, this took no convincing. Dysentery “has been more fatal to soldiers than powder and shot,” wrote William “Father of Modern Medicine” Osler in 1892. (“Dysentery” is an umbrella term for infections in which the pathogens invade the lining of the intestine, causing cells and capillaries to ooze their contents and creating dysentery’s hallmar
k symptom, the one that sounds like British profanity: bloody diarrhea.) For every American killed by battle injuries during the Mexican War of 1848, seven died of disease, mostly diarrheal. During the American Civil War, 95,000 soldiers died from diarrhea or dysentery. During the Vietnam War, hospital admissions for diarrheal diseases outnumbered those for malaria by nearly four to one.

  Once germ theory gained acceptance and the mechanics of infection became known, microorganisms—and the filth they breed in, and the insects that deliver them—became targets of military campaigns. Suddenly there were Fly Control Units, sanitation officers, military entomologists. The US military has been involved in most of the major advances in preventing, treating, and understanding diarrheal disease. Cairo’s NAMRU-3, the parent unit of Mark Riddle’s humble container lab in Djibouti, has a four-star antidiarrheal pedigree. Its first director, Navy Captain Robert A. Phillips, figured out that adding glucose to rehydration fluids enhances intestinal absorption of salts and water. This meant rehydration could be achieved by drinking the fluids rather than making one’s way to a clinic to have them administered intravenously. This has been a lifesaver not only for people who fight in remote, medically underserved areas but for people who live there. A 1978 Lancet editorial called Phillips’s discovery “potentially the most important medical advance this century.”

  The full name of Riddle’s study is Trial Evaluating Ambulatory Treatment of Travelers’ Diarrhea (TrEAT TD).* “Travelers’ diarrhea” is another catch-all term. Most of it—at least 80 percent—is bacterial, with 5 to 10 percent viral (vomit typically joining the waterworks here) and a miscellaneous percentage from protozoa like amoeba or giardia. All of it is caused by contaminated food or water. There used to be a separate category called “military diarrhea” (military referring to the patients, not the explosive nature of their evacuations), but if you look at the responsible pathogens, the breakdown is almost the same. Military diarrhea is travelers’ diarrhea, because service members are travelers—in places where you don’t want to be drinking the water. A survey conducted by Riddle, David Tribble,† and others with the US Naval Medical Research Center revealed that from 2003 to 2004, 30 to 35 percent of military personnel in combat in Iraq experienced situations where they lacked access to safe food and water. In the early days of a conflict especially, combatants are like backwater backpackers, crapping in the dirt and waving the flies off whatever food the locals are peddling. In that same survey, 77 percent of combatants in Iraq and 54 percent in Afghanistan came down with diarrhea. Forty percent of the cases were serious enough that the person sought medical help.

  For every person who shows up at morning sick call, four tough it out. Riddle would like to know why. The average bout of travelers’ diarrhea lasts three to five days. Why endure this, when some of the new antibiotics, Riddle’s data show, can have you back to normal in four to twelve hours? He’s been asking around, mostly at mealtimes. The tables in the hangar-size Dorie‡ are arranged church basement–style, in long rows, so there’s always a friendly stranger across from you or at your elbow, someone new with whom to chat about loose bowel movements while you eat.

  Riddle gets right into it this morning with the man to his left. The uniform identifies the man as a Marine sergeant, last name Robinson. “I’m in the Navy,” Riddle is saying, “and we’re looking at simplified treatment regimens for travelers’ diarrhea. We’re finding that a single dose of antibiotic and an anti-motility . . .”

  Robinson looks up from his eggs. “Anti—?”

  “Like Imodium,” I offer. “Stops you up.”

  “Oh, absolutely not. You do not want to mess with Nature like that.” Robinson has the booming vocals and commanding bullnecked air of the actor Ving Rhames. One imagines Riddle going straight over to the lab after breakfast and tossing his data in the trash—What was I thinking?

  “You have something bad in you, bad water or what have you? You got to pass it.” It’s like discussing diarrhea with the Giant Voice. “Defeat the purpose if you mess with that.”

  We’ve been hearing this a lot. People think diarrhea is the body’s attempt to rid itself of invaders, or to flush out the toxins they produce. They won’t take an antimotility drug like Imodium because they think it interferes with the purge. But diarrhea is not something you are doing to pathogens; it is something they are doing to you. In varied and dastardly ways. Shigella and campylobacter, two common causes of bacterial dysentery, wield a toxin-delivering “secretion apparatus”—a hypodermic-cum-bayonet that injects toxins into cells in the intestinal lining, killing them and causing the fluid inside them to spill out. That spillage is part of the watery-stool scenario, but there’s more! With enough of those cells out of commission, the large bowel can no longer perform its duty as an absorber of water. Instead of food waste getting drier and more solid as it moves along the gastrointestinal tract, it stays liquid all the way along. The bacterium called enteroaggregative E. coli produces the same effect, in a different manner. It becomes a living cling wrap, a bacterial phalanx that coats the intestine and blocks absorption. Vibrio cholera and enterotoxigenic E. coli, or ETEC, inflict chemical weapons: Both produce a toxin that hijacks the pump that maintains cellular homeostasis. The commandeered pump begins pulling water out of cells faster than patients can replace it by drinking.§

  Why do these creatures do this to us? Is there an evolutionary motive? Sure, says Riddle. There always is. By causing humans to produce liquid feces, feces that splatter and flow and coat a larger surface area, a pathogen speeds its spread. Cover the world! The bacterium that causes cholera is especially proficient. Cholera patients decant as much as five gallons of liquid a day. The efflux is so torrential that one of Dr. Phillips’s Navy colleagues was inspired to invent the cholera cot, an army-style cot with a hole cut out under the buttocks. (Bucket sold separately.) The cots, still made today, allow patients to “go to the bathroom without leaving the bed,” writes specialneedscots.com, taking euphemism into the realm of quantum physics.

  Besides, enteric bacteria are not easily flushed out. They’ve evolved ways to hang on in the deluge. ETEC—the bacteria behind as much as half of all travelers’ diarrhea—are equipped with a hairlike grappling hook called a longus, which they use to pull themselves close to a cell wall. On receipt of a chemoelectrical signal from the cell, the bacteria sprout springy hairs called fimbriae, with suction cups at their ends. Your immune system, for its part, has more sophisticated defenses than simply hosing down the premises. It starts cranking out specially designed antibodies. One might target the suction cups and keep them from adhering. Another might gum up the longus or disable the toxin.

  Sergeant Robinson has nothing more to say about diarrhea, but he would like Riddle to have a word with the people responsible for the packet of toilet paper in the combat field rations, or MREs (Meals, Ready-to-Eat). “It’s like this much.”¶ He tears off a piece of napkin the size of a drink ticket. “To wipe your ass!” Riddle volunteers that Navy guys pack baby wipes. He may regret saying this, because Robinson counters that Marines just cut off a piece of their t-shirt. Which possibly sums up the whole Marine Corps–Navy relationship.

  Riddle thanks Sergeant Robinson and makes to leave. He likes to get back to his quarters before 8:00 a.m., when the national anthems—first Djiboutian, then American—begin playing over the Camp Lemonnier public address speakers. All those outdoors have to stop what they’re doing and stand respectfully until the music stops.# The Djiboutian national anthem is a melodic, sweeping number, like the theme song to an old TV western. The whole thing isn’t played, but it can seem that way should you be having some “postprandial urgency.” Meals—particularly the big ones occasioned by all-you-can-eat chow-hall buffets—trigger the gastrocolic reflex, a major move-along of the contents of the large intestine. Ushering out dinner to make room for breakfast. If, on top of that, you have a touch of irritable bowel syndrome (IBS), there may be times when all the patriotism in the land won’t keep you standin
g through the final bars.

  During his years at NAMRU-3 headquarters, in Cairo, Riddle regularly got hit with diarrheal infections, a result of “sampling the fecal veneer” at local eateries. Irritable bowel syndrome is a well-documented, little-publicized aftermath of diarrheal infections—especially severe or repeated bouts. If you talk to people who’ve recently been diagnosed with IBS, about a third of them will say that their symptoms began after a bad attack of food poisoning. Defense Department databases reveal a five-fold higher risk of IBS among men and women who suffered an acute diarrheal infection while deployed in the Middle East. Even the Veterans Administration recognizes IBS—as well as a form of arthritis called “reactive”—as one of the “post-infectious sequelae” of enteric infections. If patients can show that the condition developed following an infection with shigella, campylobacter, or salmonella during deployment, they’re entitled to benefits. Riddle estimates that the Defense Department could wind up spending as much money on these long-term consequences of food poisoning as it spends on post-traumatic stress disorder.

  Why not prescribe antibiotics more widely? First, there’s the issue of antibiotic-resistant strains developing, though this is less of a concern with some of the newer regimens that wipe out infections in a single day—likely not enough time for a resistant strain to evolve and thrive. More worrisome, perhaps, is recent research showing that the colons of overseas travelers who treat their diarrhea with antibiotics, particularly in Southeast Asia, tend to become colonized with two species of “bad” bacteria that they then carry home and can spread around town. Both bugs may inhabit a traveler’s gut only briefly and cause no problems while they’re there, but they are dangerous to patients with weak immune systems. Here again, with the newer single-dose regimens, it may not be an issue.