Faking Sick for a Living

Lying to your doctor is encouraged in one situation: when your doctor is a student and you're an actor asked to portray a certain condition. My friend Amy Savage does this for work. In between fake symptom bouts, I asked her to write a guest post sharing what she's learned from being poked for practice.

Have you ever been asked to “please dislocate your left breast,” or if you “have noticed any hairs growing in places you normally wouldn’t have hairs"? Or maybe someone told you to “have a nice day” after your spouse just passed away or you’d received a cancer diagnosis. Not only do I hear things like this from time to time at my job, but I have grown to expect them.

I have been working for several months as a so-called standardized patient. The local medical school runs an excellent program that lets students conduct histories and physical exams in a simulated, standardized setting. This means I (and many others) pad around in rubberized socks and breezy hospital gowns and feign myriad diseases, syndromes, conditions, and (sometimes nasty) habits. It also means I overuse hand sanitizer and have many strangers listen to my heart, palpate my abdomen, and poke me with a broken wooden Q-tip to test my sensation. One time I even let someone stick their gloved hand in my mouth and squeeze my tongue a little.

As a standardized patient, I have to memorize case materials for fictional patients. This means memorizing not just a list of symptoms and how long the “patient” has had them, but also the patient’s occupation, education, diet, marital status, drinking habits, exercise, stress, family history, and past medical history. If I am supposed to experience or not experience pain when they poke me, or have a knee jerk reaction (literally), I’d better be ready with a realistic response. This involves a bit of groaning, some crying (in the case of bad news), and some bona fide reflexes.

Most often the students show concern and empathy. In the rare case, though, that they say something a patient could perceive as judgmental, we “patients” get to act grumpy and less compliant.

I am expected to give specific, memorized lines about my symptoms, but only if the students ask the right questions in the right way. For example, if a student asks if I use tobacco, that is different from asking if I use or have ever used tobacco products. Asking a woman if she has ever been pregnant is different from asking if she has any children. And, of course, those types of oversights in questioning can lead to different diagnoses.

Luckily, I am not just a living cadaver for the medical students to practice on. I also give feedback. We evaluate the students on things such as how they organize their questions; whether they display empathy; how they perform the physical exam; and how they communicate the possible diagnoses to the patient. After the exam we have time for students to ask questions and for the standardized patients to give suggestions—like how to encourage patients to change their habits, or what would be better wording to deliver bad news.

From this experience, I have learned what to expect from an ideal physician, what to ask, and what not to tolerate. For example, your doctor should not ask leading (or possibly judgmental) questions such as, “You don’t smoke, right?” Nor should they run off a list of questions such as, “Do you smoke, drink, or use drugs?” without giving you time to think. They should ask open-ended questions: “Have you noticed any other changes lately?”

I've also learned that it's important to pay attention to symptoms that may seem unrelated to your chief complaint. If you were experiencing extreme fatigue, for example, you might not think that your newly brittle hair had anything to do with your energy levels, but it could be a thyroid problem.

Even though I am trained to train medical students, this only means I know what (or how) they are supposed to ask or not ask. It did not necessarily mean I knew what to ask when I saw my own doctor.

Recently, I went to my own physician for knee pain. The doctor instructed a medical student to ask about my symptoms while she (the doctor) went out of the room, presumably to doctor someone. The medical student reviewed my complaints. What made the pain better? Worse? Did the knee make any sounds? The student said that it sounded like a very common problem; she just couldn’t remember the name exactly. (Whether she really couldn’t remember or was refraining from diagnosing me without a medical license, I will never know.)

The student left to get the doctor, and when they returned the doctor moved my knee cap around a bit and then suggested that I might have premature arthritis (I’m close to thirty) and that I may need cortisone shots and physical therapy. I refused to believe this, but said “Oh, okay,” nodding complacently. The student and the doctor left the room to give me time to get my pants on, and when they returned, the doctor admitted that the medical student had come up with another possibility: runner’s knee. I read the photocopied pamphlet they handed me, and it fit all of my activities and symptoms.

I was grateful that my physician was willing to listen to the medical student, though a bit terrified to think what I would have put myself through if she hadn’t. Though I know better now from my work as a standardized patient what the doctor could and should ask me, I am still at their mercy if they do not ask the right questions and listen carefully to the answers.

**********

How to Make Your Doctor’s Appointment Better Than Standard: Advice from a Standardized Patient

• Find a physician who will ask you many questions and listen carefully to the answers. Do not assume, if you’ve talked to a medical student or other proxy, that they have conveyed all the information to the physician.

• Your physician should give you more than one possible diagnosis. In other words, they should tell you what they are thinking, unless they are absolutely certain what is wrong. This should be like a conversation between you and your physician. Don’t be afraid to ask, “Are there any other possibilities for what this could be?”

• Pay attention to your own body. Notice when the pain started and what makes it better or worse. Does it happen at a certain time of day or after certain activities? Have you changed your diet recently? Tell your physician about everything you’ve noticed that is not normal for you, even if you don’t think those other symptoms or changes are relevant.

• As I learned with my knee problem, some medical students—because they are not overly confident and are willing to ask, not assume—are better than some doctors.


Image: Craig Breil/University of Michigan MSIS (not a picture of Amy)

Why It's Nearly Impossible to Castrate a Hippo

Chances are you've never wondered how difficult it is to remove the testes of a hippopotamus. Other people have been thinking hard about it, though, because in fact it's almost impossible.

Before sitting down to emasculate a common hippopotamus, Hippopotamus amphibius, it would be reasonable to ask why. They're a threatened species, so usually conservationists try to make more baby hippos—not fewer. But in zoos, hippos turn out to be prolific baby-makers. Females can live for 40 years and may birth 25 calves in that time. This would be great news in the wild, but zookeepers don't always have someplace to store a new two-ton animal.

Male hippos can also be aggressive toward each other, at least while they have all their man parts. For both of these reasons, zoos may want to have their male hippos fixed. But there are a few factors working against them, explains a new paper in the journal Theriogenology (that's reproductive science for vets) by an international group of authors.

The first challenge is that hippopotamuses hide their genitals. The testes are inside the body, instead of outside in a scrotum. (Other mammals in the internal-testes club, since you asked, include the armadillo, sloth, whale, and platypus.) This makes the hippo's testes totally invisible from the outside. Combined with a penis that the paper's authors describe as "discreet," it means it's hard to tell males from females at a distance.

Another problem is that testes aren't in the same place from one hippo to the next, and they may "retract" even farther during surgery. Hippopotamuses are also difficult to safely put to sleep. "In the past, hippopotamus anesthesia has been fraught with serious complications," the authors explain.

After moving past the anesthesia problem (they used an apparently safer blend of drugs, delivered via a dart to the hippo's ear), the researchers turned to the anatomical problems. Their answer was ultrasound. Once they had positioned the animal, they used ultrasound imaging to find the testes—then used it again after cutting into the hippo, if the testis they were looking for had scooted farther away from them.

Even after finding the sneaky organs, the procedure wasn't simple. The depth of the testes' hiding places varied by as much as 16 inches from one hippo to the next. Everything had to be done deep inside the animal's body, making it hard to see what was going on. "Grasping the testicle with forceps proved laborious" in most of the animals, the authors write. They also mention using a "two-handed technique" and "moderate traction." The whole hour-and-a-half procedure, based on a method for castrating horses, is described in detail for anyone who wants to try it themselves.

All ten hippos in the study were successfully castrated, though one died shortly afterward, following a complication from a unknown pre-existing condition. Over the next six months, the authors checked in with the zoos housing the hippos to see whether their behavior or interaction with other animals had changed. There were four cases where zoos wanted their hippos fixed to ease aggression between males; in all four, the problem seemed better. (One zoo, though, reported that castrated males were harassed more by females.) Overall, the authors think their technique will help zoos take better care of their hippos.

The final challenge to hippopotamus surgery—what should be a challenge, anyway—is that the animals spend most of their time in a pool of water packed with feces. The animals in the study lowered their stitched-up bellies into this infectious slurry as soon as they had a chance. Yet all of them healed from surgery without trouble. Hippos in general seem to be especially good healers, the authors write.

A possible explanation for the animals' healing superpower is the "red sweat" or "blood sweat" that oozes from their skin. It's not really sweat and it doesn't contain blood, though it is red. The pigments in this skin secretion have been found to absorb UV light, making the "sweat" a potential sunscreen. The pigments can also keep bacteria from growing. So a built-in antibiotic may be what keeps hippos from getting infections after they tussle and bite each other (or after meddling vets come and cut out their manhood). However the red sweat works, it shows that a hippo's secrets don't end with the location of his testicles.


Images: Charlesjsharp (via Wikimedia Commons); drawings by Eva Polsterer (from Walzer et al.).

Walzer C, Petit T, Stalder GL, Horowitz I, Saragusty J, & Hermes R (2013). Surgical castration of the male common hippopotamus (Hippopotamus amphibius). Theriogenology PMID: 24246424

Higher Altitude Protects Teens from Concussions

The human brain is a vulnerable thing, perched in its peanut shell on top of our walking, stumbling bodies. Humans who enjoy collision-heavy pastimes—say, tackle sports—put their brains in particular danger. And when it comes to concussions, young people are at even more risk than adults. Yet kids who play at at higher altitudes seem to be safer than their peers. The reason, hidden somewhere in the brain's squishy dynamics, might help protect kids and adults who are smashing into each other everywhere.

You don't have to travel to Denver's Mile High stadium for your body to start responding to altitude. "Relatively small changes in altitude can have significant changes upon the physiology of the body," say Gregory Myer and David Smith, both in the sports medicine department at Cincinnati Children's Hospital Medical Center. (The coauthors responded to my email jointly.)

At just 600 feet above sea level, the authors point out, oxygen in the atmosphere has already dropped from 21 percent to 20 percent. Your body notices this slight change and adjusts. One measure it takes, upon noticing there's less oxygen available than usual, is to send a little more blood to your brain. "This leads to a slight filling up of the brain space," Myer and Smith say. Your brain ends up squeezed just a tad more tightly into your head.

Wherever you are, if you get suddenly knocked on the head, your brain will ricochet around inside your skull's fluids. In actual scientific terms, it "sloshes." The delicate brain squishes and twists, and hosts of neurons fire all at once. You may black out. Afterward, you might have memory loss, confusion, nausea, dizziness, and other symptoms that can last for days or months. The looser, stretchier blood vessels in the brains of people under age 20 may explain why they're at even greater risk.

Concussions might be prevented if the skull could keep the brain from sloshing by holding onto it a little tighter—as it does at higher altitudes. To find out whether this works, Myer, Smith and their colleagues used data from the National High School Sports-Related Injury Surveillance System. Run by the University of Colorado, Denver, this study collects data on injuries from high schools across the country.

The authors looked at nearly 6,000 concussions from about 500 schools. The concussed kids were athletes in all kinds of sports, at schools ranging from sea level to 6,900 feet. When the researchers divided student athletes into those living above and below the median altitude—which was 600 feet—they saw a significant difference in concussions. Across all sports, kids at higher altitudes had a 31 percent lower risk of concussion. Among football players only, the results were essentially the same: a 30 percent lower risk at higher altitude.

It's an intriguing difference. As sports organizations and the public learn more about chronic traumatic encephalopathy (CTE) and the long-term risks for athletes with head injuries, the quest to prevent concussions is growing more urgent. High schoolers, though, don't travel to play like professional athletes do. Could some of their lower risk have to do with changes in their bodies that happen over a lifetime of living at a certain altitude? "Visiting altitude will begin creating a tighter fit the minute you arrive," Myer and Smith say. However, adjustment happens over the long term too. "Everyone is likely different in how quickly they respond [to altitude] and how protection occurs for them," the authors say. "This is why we are working to evaluate technologies that can give this same protection whether you are in Denver or Miami." They'll be looking next at adults and professional athletes to try to find answers.

One hint comes from an earlier study David Smith performed on rats. While wearing a collar that slightly squeezed their jugular veins, the rats were hit hard on the head. The collar seemed to make rats less vulnerable to concussion, apparently because more blood was in their heads, squeezing their brains more tightly and preventing sloshing. This all sounds pretty unpleasant for the rats, but Myer and Smith insist that "the technologies we are studying are no more risky than yawning or even the act of lying down."

Animals like woodpeckers and head-ramming sheep manage to protect their brains from damage, the researchers point out. So why can't we? Of course, in our case the head ramming is in the name of fun. But there might be ways to safeguard our brains, like these animals do, from the inside out.


Image: Rocky Mountain High School in Colorado, by Paul L. Dineen (via Wikimedia Commons)

David W. Smith, Gregory D. Myer, Dustin W. Currie, R. Dawn Comstock, Joseph F. Clark, & Julian E. Bailes (2013). Altitude Modulates Concussion Incidence: Implications for Optimizing Brain Compliance to Prevent Brain Injury in Athletes. Orthopaedic Journal of Sports Medicine DOI: 10.1177/2325967113511588

On the Road with the Shambulance

Hello from the land of boxes!

I'm about to move across the country, so there will be a brief hiatus from new stories here. But in the meantime, please enjoy some travel-themed reruns.

The Shambulance is a vehicle with an identity crisis (it might travel by land, sea, or space, and is potentially horse-drawn). It's also a series on this blog examining dubious health fads. Below, you'll find its complete voyages.

It has been, I think you'll agree, a twisted journey.

* * * * * * * * * * * * * * *

Ionic Foot Detox Baths (June 2012)
Hint: Don't.

Ab Toning Belts (or, Muscle Tone Is All in Your Head) (July 2012)
This goofy infomercial product blew my mind. But not because it works.

Zero-Calorie Noodles? (August 2012)
The only Inkfish post ever to involve a taste test.

Infrared Body Wraps (September 2012)
Be glad this doesn't work.

5 Reasons Not to "Cleanse" Your Colon (October 2012)
#3: It's rude to firehose your friends.

Copying Roger Clemens Won't Help You Lose Holiday Pounds (November 2012)
The dirt on vitamin B12 shots.

Enough Already with the Juice Cleanses (January 2013)
In which a salesperson suggests I fast for five straight weeks.

Deer Antlers Are Not Unicorn Horns (February 2013)
Some professional athletes are confused about this.

Reflexology and Other Stories (April 2013)
Non-traditional non-Chinese medicine.

Laser Lipo Only Kind of Sucks (July 2013)
Surprisingly, the least sketchy place the Shambulance has traveled.

If you'd like to suggest a future destination for the Shambulance to drive, climb, dive, or teleport to, leave your suggestion in the comments!


Image: taken by me with my iPhone because we already packed the camera cord.

The Shambulance: Laser Lipo Only Kind of Sucks

The Shambulance is an occasional series in which I try to find the truth behind overhyped or bogus health products. With me at the reins are Steven Swoap and Daniel Lynch, both of Williams College.

People selling no-suction liposuction are not totally sure what they're offering you. "Low levels of visible red laser light...create a safe and painless bio-stimulation effect," says one center. "Transitory pores" open in the fat cells, sending their contents out for "detoxification," says another, adding that the process is "almost exactly the same as exercise." Except for the lasers.

Despite the confusion, laser lipo does—seemingly, in some ways—work. Wait! Don't panic. Put away your wallet and let's talk about it.

"This is not a weight loss therapy," says Williams College physiologist Steven Swoap. At best, it's "a redistribution of fat therapy."

Many spas offer treatment with a specific laser system called i-lipo. The FDA approved this device in 2012 "for non-invasive aesthetic treatment for the temporary reduction in circumference of the waist."

It's "non-invasive" as opposed to something called laser-assisted liposuction, where doctors blast your fat with a laser before actually cutting into you and sucking it out. What about the rest? "Aesthetic" is because this is meant to change your looks—not to address any health problems. "Temporary," because the FDA based their approval on a study lasting just a few weeks. If you want your new waist shape to last longer, they're not making any promises. And, of course, "reduction in circumference"—but not loss of weight. Something inside you may move around, but that doesn't mean it's going away.

FDA approval was based on a placebo-controlled study in which some participants had a fake laser treatment. After eight sessions over three to four weeks—each session followed by a required workout—the group getting real laser treatment had lost almost an inch and a half more from their waists than the placebo group. (If anybody finds this study itself, and not just a PR summary, I'd love to see it.)

As for how it works, the FDA approval statement says that laser energy "promotes disruption" of fat cells, making them release their contents. But a 2013 review paper says that "the mechanism of action of LLLT [low-level laser therapy] on fat remains somewhat controversial." Various scientists have suggested that the laser makes tiny pores open in the fat cells to release fats; that the cells themselves are destroyed; or that the laser stimulates your cells' machinery to start breaking down fats and discarding their components. There are challenges to the evidence in every camp.

"The use of lasers to essentially heat the fat seems a bit dubious," says Williams College biochemist Daniel Lynch. He's curious whether the results could really be coming from changes in water and salt balance in heated areas of the body. "I wonder if similar effects could be obtained simply [with] heating pads," he adds. Actually, the so-called infrared body wraps offered by some spas aren't far off—these places wrap clients in heated pads and report inches lost after all the squishing and sweating is over.

Assuming that the procedure does kick fat out of your cells, many spas recommend that you exercise immediately afterward. You need to burn up that wandering fat right away, they warn, or else it will just find its way home to your belly.

Lynch agrees that mild exercise afterward would help you use up any fats that the laser has shaken loose. Swoap points out that when we do tougher exercise, our bodies switch to using carbs as fuel instead of fats—so an intense workout right after laser treatment would be less helpful than a tame one. Either way, if fatty acids travel to your liver, it will likely send them right back into storage in your body's squishy areas.

Even if you manage to lose fat from your midsection, you may not be doing yourself any favors in the long term. "Certain types and locations of fat are beneficial, whereas others are harmful," Swoap says. The fat that's reachable by liposuction—laser or traditional—is "subcutaneous" fat, just under your skin. "Subcutaneous fat is a good fat—[it provides] insulation, cushioning, even endocrine function," Swoap says.

"Liposuction is, unfortunately, removing mainly subcutaneous 'good fat' in the name of body sculpting and body image," Lynch agrees.

The fat that's harmful to your health is "visceral" fat, the stuff wrapped around your organs. And if you suck out subcutaneous fat, your body may respond by hiding more fat where you can't reach it.

A 2011 study found that one year after surgical liposuction in their thighs and bellies, women had regained their lost fat—and stored more of it into their abdomens than originally. In 2012, a different research group found that six months after abdominal lipo, women's visceral fat had increased by 10%. This was prevented if they followed an exercise program.

So laser lipo may shrink your waist a little, if you exercise every time you do it. And fat removed surgically might not reappear to strangle your organs, as long as you keep exercising after liposuction. There's no word yet on whether laser lipo can also lead to more visceral fat, but to be safe you might just want to keep working out after it's done.

Maybe the people who called this treatment "almost exactly like exercise" were closer than they knew.


Image: NU:U Laser Lipo Centers

Runners: Stop the Pronation Panic

If you walk into a sporting goods store and ask for shoes, you're likely to be thrown on a treadmill and have your strides dissected on video as if you were crossing an Olympic finish line. Salespeople will give you a thorough analysis of your gait. They may break the news that you "over-pronate," rolling your foot inward to some degree at the end of each step. Don't worry! It's common—and they sell a shoe made for your specific flaw. It's all very scientific, except that it isn't.

Rasmus Nielsen, a sport science graduate student at Aarhus University in Denmark, has seen the process from both sides of the in-store treadmill. When he first started running, he was told he should buy motion-control shoes to correct his pronation. Five years later, he started working in a running store.

"I was told to advise individuals to buy stability or motion control shoes if they were pronators," Nielsen says. "I started to ask the question, 'Why do we do this?' No evidence-based answer was provided."

Since becoming a physical therapist and seeing thousands of runners in his clinic—and dealing with his own running injury—Nielsen has developed a new perspective about where injuries come from. He doesn't think pronation or supportive shoes matter much at all. To add some evidence to the discussion, he conducted a study of more than 900 novice runners.

The subjects were healthy Danes of various ages and sizes—on average, 37 years old with a BMI of 26—who didn't run before the study. Physical therapists assessed their gaits and scored each person's feet as neutral, moderately or highly pronated, or moderately or highly supinated (rolling outward). Then subjects spent the next year running as much as they wanted. They logged their miles with a GPS watch and called the study leaders for an appointment if any injury cropped up.

Whatever their gait, all subjects were given identical "neutral" running shoes. Nielsen reasoned that if matching running shoes to foot type prevents injuries, then people with pronating or supinating feet should injure themselves sooner in these shoes than people with neutral feet.

That didn't happen.

Injuries were common; more than a quarter of the new runners were sidelined by injury at some point. But people's foot types had no relation to how soon they got injured. In fact, pronators had slightly (but significantly) fewer injuries per thousand kilometers run than neutral runners did.

Nielsen isn't the first researcher to find plot holes in the story told by shoe companies. A 2009 review concluded that there was no evidence behind the way different shoe types are prescribed. In 2011, a study of female runners found that those randomly assigned to wear motion-control shoes experienced more injuries than those assigned to other types of shoes.

Since the current study only involved uninjured, novice runners, the authors point out that motion-control shoes could be helpful to people who've already had an injury. It's also possible that the most extreme pronators are more prone to injury; in the study, this group was so small—only 18 people—that no real conclusions could be drawn about them. Yet for garden-variety pronators, there was clearly no extra injury risk.

These days, Nielsen says he can run in any type of shoe, once he gets used to it. He thinks how people train matters much more for their injury risk. Worrying about your sneakers, he says, isn't worth it. "I would definitely advise other runners [to do] otherwise than I did."


Image: by Danielle Walquist Lynch (via Flickr)

Nielsen, R., Buist, I., Parner, E., Nohr, E., Sorensen, H., Lind, M., & Rasmussen, S. (2013). Foot pronation is not associated with increased injury risk in novice runners wearing a neutral shoe: a 1-year prospective cohort study British Journal of Sports Medicine DOI: 10.1136/bjsports-2013-092202

Everyone Underestimates Fast-Food Calories (But Especially at Subway)

At a McDonald's shareholder meeting last week, a nine-year-old girl accused CEO Don Thompson of sneaky advertising. Stop "tricking kids into eating your food," she demanded, saying that McDonald's ads tell kids to "keep bugging their parents" until they get that Happy Meal. In the world of fast-food chains, though, the golden arches may not be the sneakiest purveyor of excess calories. Diners in all kinds of fast-food restaurants underestimate the calories they're taking in—and the most dramatic underestimation happens at Subway.

Thompson may not have been swayed, but Jason Block of Harvard Medical School and a group of other researchers writing in BMJ do care what consumers think about their fast food. Specifically, they care how many calories people think they're eating. To find out, they went into the trenches: 80 fast-food restaurants in New England cities.

Researchers stood outside their chosen dining establishments (which included McDonald's, Burger King, Subway, Wendy's, KFC, and Dunkin' Donuts) in 2010 and 2011. They asked customers on their way in whether they'd be willing to save their receipts and answer a few questions when they came back out. (Only a few restaurants kicked the researchers off the premises.) At dinnertime, they targeted adults, either eating on their own or with kids. At lunchtime and after school let out, they went to fast-food places within a mile of a school and talked to adolescents.

In all, more than 3,000 people participated. Across all the restaurant chains, the average dinnertime meal for adults was 836 calories, and the average afternoon meal for adolescents was 756 calories. Yet when asked how many calories they thought their meals held, people consistently guessed too low. And the bigger their meals were, the more severely they underestimated.

The researchers also asked subjects whether they'd noticed any calorie information indoors. "All of [the chains] provide information in some way," says Block—"on a wall poster, on napkins/cups, on sandwich wrappers and tray liners, and on 'special menus' that might present items that are below a certain number of calories."

Yet less than a quarter of adults said they'd even noticed this information. Those people didn't do any better at estimating their calories than others. Did they use the information to help them make menu choices? Only five percent of all adults said yes. Of adolescents, two percent.

Block says it's easy for diners to miss the calorie information provided by fast-food chains today. But soon, as part of the Affordable Care Act, all chain restaurants with more than 20 locations will have to post calorie information in a standard format. "The menu labeling regulation will require the calories to be up front and highly recognizable," Block says.

Even this kind of prominent labeling has had mixed results in past studies. However, Block adds, the new law will also require menus to post an "anchoring statement" pointing out that people only need about 2000 calories a day. This might make, say, the 970 calories in a Wendy's Baconator more meaningful to a customer.

Anchoring was effective in at least one small study, Block says. Other studies have looked at "traffic light" labeling (in red, yellow, or green), or listing calories in terms of how much exercise you'd need to burn them back off. "We'll be in a position to know much more after the federal law is implemented," Block says. His group is collecting data this year and next year to see how well the new labeling works.

If people do start noticing how many calories their favorite chains are offering, they may be surprised. When researchers broke down their results by restaurant chain, they found that people underestimated their calories more dramatically at some restaurants than others. At McDonald's, adults guessed too low by an average of 100 calories, and adolescents by a little more than 200. The guesses were off by a bit more, on average, at Burger King and Wendy's. At Subway, the errors were most extreme: adults underestimated their calories by an average of about 350, adolescents by close to 500.

Five hundred calories is equivalent to all the bread in a 12-inch sub (or, if you opt for multigrain, all the bread plus four American-cheese triangles). It's a lot not to know you're eating. This mistake, the authors write, may happen because people view Subway with a "health halo." After seeing TV ads featuring fresh vegetables, smiling Olympians, and Jared's old pants, consumers may think they're making a healthier choice than they are.

The new calorie labeling could help most in places like this. A fast-food chain that brands itself as healthy is even sneakier than someplace like McDonald's, which even little girls know is bad for you.


Image: by Jeremy Brooks (via Flickr)

Block, J., Condon, S., Kleinman, K., Mullen, J., Linakis, S., Rifas-Shiman, S., & Gillman, M. (2013). Consumers' estimation of calorie content at fast food restaurants: cross sectional observational study BMJ, 346 (may23 3) DOI: 10.1136/bmj.f2907

The Shambulance: Reflexology and Other Stories

The Shambulance is an occasional series in which I try to find the truth about bogus or overhyped health products. Helping me keep the Shambulance on course are Steven Swoap and Daniel Lynch, both biology professors at Williams College.

Sticking a Q-tip up one’s nose is not the source of many great insights. Yet it’s how an American doctor in the early 20th century developed the theory that became modern reflexology. He would be proud—though maybe a little confused—to see people today flocking to reflexology spas, where practitioners treat all their problems via the soles of their feet.

The American doctor in question was William H. Fitzgerald, an ear, nose and throat specialist. In a 1917 book, he explained the genesis of his big idea:

Six years ago I accidentally discovered that pressure with a cotton tipped probe on the muco-cutinous margin (where the skin joins the mucous membrane) of the nose gave an anesthetic result as though a cocaine solution had been applied . . . Also, that pressure exerted over any bony eminence of the hands, feet or over the joints, produces the same characteristic results in pain relief . . . This led to my ‘mapping out’ these various areas and their associated connections and also to noting the conditions influenced through them. This science I have named "Zone Therapy."

Chapter titles from Zone Therapy include "Zone Therapy for Women" (tongue depressor into the back of the throat for menstrual cramps), "Painless Childbirth" (rubber bands around the toes, among other interventions) and "Curing Lumbago with a Comb."

A nurse and physical therapist named Eunice D. Ingham extended the idea of zone therapy in the 1930s and 1940s, eventually mapping the entire body onto the soles of the feet. She called each important point on the foot a “reflex” because it reflected back to a certain organ or body part. Ingham wrote two books on the subject, now called reflexology: Stories the Feet Can Tell and Stories the Feet Have Told.

Today, the International Institute of Reflexology describes its practice as as “a science which deals with the principle that there are reflex areas in the feet and hands which correspond to all of the glands, organs and parts of the body.” Stimulating these points “can help many health problems in a natural way.” The site insists, “Reflexology…should not be confused with massage.”

There has been some confusion and blending, though, between Western reflexology and traditional Chinese medicine. Ingham and Fitzgerald's idea of "zones" is similar to the Chinese principle of "meridians." In traditional Chinese medicine, meridians are paths that carry qi through the body and connect the acupuncture points. Reflexology groups like to say that Fitzgerald "rediscovered" the science from more ancient roots. They even claim that ancient Egyptians practiced it, based on tomb paintings showing people holding each other's feet.

Whoever thought it up first, the idea that the soles of your feet hold a miniature map of the entire rest of your body defies a scientific explanation.

“The problem is communication,” says physiologist Steven Swoap. “How does the foot talk to the pancreas?”

The foot is full of sensory nerves, Swoap explains. These can detect temperature, pain or position and send that information to the spinal cord. If the signal is something urgent—say, you stepped on a nail—the spinal cord will send a quick command back to the foot (“STOP!”). If the signal from the foot is a non-painful one (“Hey, I’m walking on grass”), it will travel all the way up the spinal cord to the brain.

“But in no instance do those sensory nerves bypass either the spinal cord or the brain and go directly to the liver, or the kidney, or the colon,” Swoap says. This means your foot can’t communicate directly with any other body part except your spinal cord or brain. Whatever stories the feet have told, they’ve had a limited audience.

Daniel Lynch, a biochemist, points out that sex organs are missing from some reflexology maps. “Why aren’t the gonads on there?” he asks. Other maps label a "testes and ovaries" region around the middle of the heel, but there's variation from one chart to the next.

Setting aside the map itself, Lynch says, “Where is the evidence that it actually works?”

The evidence is slimmer than a stiletto heel. In a 2011 review paper, complementary medicine researchers at the Universities of Exeter and Plymouth dug up every scientific study of reflexology they could find. Out of 23 randomized clinical trials, only 8 “suggested positive effects.”

The quality of the studies was “variable,” the authors write, “but, in most cases, it was poor.” Only four studies that found a positive effect used a placebo control—that is, did massaging the feet without regard to “zones” give patients the same symptom relief? In general, studies tended to use small groups of subjects and not to be replicated by other researchers.

Reflexology has been tested on conditions including asthma, premenstrual syndrome, irritable bowel syndrome, multiple sclerosis, and back pain. If reflexology does have a benefit, “The most promising evidence seems to be in the realm of cancer palliation,” or making patients more comfortable, the authors write. Overall, though, they found no convincing evidence that reflexology has power beyond the placebo.

Not that we should thumb our Q-tip-free noses at the placebo effect. The body has an impressive power to make itself feel better based on our expectations. A foot rub from a professional may very well ease a person’s pain. If that professional says anything about zones, though, it’s only a story.


Image: Foot reflexology chart by Stacy Simone (Wikipedia)

Ernst, E., Posadzki, P., & Lee, M. (2011). Reflexology: An update of a systematic review of randomised clinical trials Maturitas, 68 (2), 116-120 DOI: 10.1016/j.maturitas.2010.10.011

Are You Healthy Enough to Be a Space Tourist?

Space travel for regular folks is almost here. But before jumping on board the nearest spacecraft, amateur astronauts and their doctors might want to consider the health risks. Although standard air travel is more boring than spaceflight, it's also less likely to shrink your bones or deform your eyeballs.

"Practically only the healthiest people have flown in space so far," says Marlene Grenon, a vascular surgeon at UCSF who researches the effects of microgravity on the body. Government astronauts go through extensive medical testing and training. But even these extra-fit fliers have suffered ailments ranging from cardiac dysrhythmia to good old-fashioned vomiting. What's in store for the rest of us?

Grenon is the lead author of a paper in BMJ asking that question. The researchers say that doctors will have plenty to consider before sending their patients to boldly go where no civilian has gone before.

"Space motion sickness would be expected to be the most common" medical problem, Grenon says, "particularly for short-duration flights." If your inner ear is easily confused by sitting still in a moving vehicle, just imagine what happens when that vehicle has no up or down.* NASA's parabolic flights—trips on aircraft that fly in steep up-and-down waves, simulating weightlessness for astronauts in training and scientists researching low gravity—have earned the nickname "vomit comets" for a reason.

Life without gravity is hard on the bones and muscles as well as the barf reflex. NASA astronauts onboard the space station exercise for two hours every day to counteract bone loss, muscle atrophy, and a decrease in cardiovascular fitness. Grenon says she doesn't yet know how weightlessness might act on people who are less fit to begin with, or overweight.

Exercise may prevent muscle atrophy but it doesn't do much for squished eyeballs. A study last year found that after a six-month space mission, astronauts were likely to have "flattened globes" and other eye problems. The shifting of fluids inside the head, free to bounce off the walls just like the astronauts themselves, might be to blame. Even after shorter trips, many astronauts reported worsened eyesight.

The authors of the new paper name several medical conditions that might worsen in microgravity. For people with diseases of the blood vessels, fluids drifting around might be dangerous. Aneurysms could rupture during takeoff. Bone loss in space could be especially bad for people who already have osteoporosis. Acid reflux could worsen when the esophagus no longer knows which way is up. And don't forget radiation exposure.

But the most ordinary complaint that might ground you is an infection. Grenon writes that even people with simple ear or skin infections should consider postponing trips to space.

That's because the immune system changes during spaceflight, Grenon says. Although these changes are not well understood, they "could place the spaceflight participants at higher risk of infection." Additionally, she says, "Some research has also hinted [at] the fact that bacteria grow stronger in microgravity." And radiation might make people more susceptible to infection—or make bacteria mutate more quickly. Overall, the changes in space favor bacteria over your immune system. These risks would be greater on longer flights.

Still want to fly? Virgin Galactic is accepting reservations. If you're willing to put down $200,000 up front, you can still get a spot on their first round of flights. For a cool million you can reserve a private trip for yourself and five friends—that's a buy-five-spaceflights, get-one-free deal. Make sure you pack enough barf bags.


Grenon, S., Saary, J., Gray, G., Vanderploeg, J., & Hughes-Fulford, M. (2012). Can I take a space flight? Considerations for doctors BMJ, 345 (dec13 8) DOI: 10.1136/bmj.e8124

Image: U.S. Air Force

*For an exceedingly thorough discussion of space barfing, as well as other bodily functions performed in microgravity, I recommend Mary Roach's book Packing for Mars.

Malaria Makes Its Victims More Tempting to Mosquitos

Think mosquitos have a special fondness for you? Do they choose to target you over adjacent humans? No matter how badly you have it, things might be worse if you were infected with malaria. New research in birds shows that malaria parasites somehow make their victims more attractive to mosquitos. After all, the parasite needs a lift to its next destination—so it forces its sick host to flag down a ride.

Malaria, one of the top killers worldwide among infectious diseases, isn't caused by a virus or a bacterium. The culprit is a one-celled protozoan, called Plasmodium, that comes in a couple hundred disease-causing flavors. Plasmodium falciparum is the species that causes most malaria deaths in humans.

Various other Plasmodium species infect birds, reptiles, and mammals ranging from apes to anteaters. Whichever animal it prefers, the parasite needs to travel to new hosts via the belly of a mosquito. If possible, Plasmodium shouldn't just rely on chance—it should encourage mosquitos to bite its host.

In a 2005 study, researchers found hints that mosquitos are more attracted to the smell of a malarial child than a healthy one. (This was only true once the parasite had reached the right life-cycle stage for spreading to other people.) Giving malaria to kids is hard to justify ethically, though, even if you then treat them with antimalarials as those researchers did.

To pursue the question without leaving behind a trail of sick children, researchers in France turned to birds. Author Stéphane Cornet, of the Centre d'Ecologie Fonctionnelle et Evolutive, says the avian malaria parasite the team used infects more than 30 bird species around the world. For their experiments, they used canaries.

Mosquitos could prefer sick animals simply because they're easy targets. "Infection often renders hosts lethargic, as we are when we feel sick," Cornet says, "so that they are less able to defend themsleves against [mosquito] attacks." But he and his coauthors were more interested in whether malaria changes the particular bouquet of an animal to tempt to passing mosquitos. So they placed all their canaries inside PVC tubes with only their legs sticking out. This way, the birds' behavior and appearance wouldn't matter.

Fifty canaries were divided into pairs. Then the researchers released 70 hungry female mosquitos into a cage with each pair of birds (or, from the mosquitos' perspective, a cage holding four bird legs). After the mosquitos had feasted, the authors checked the DNA of the blood in their bellies to find out which bird each mosquito had chosen. Every mosquito choice test was repeated three times.

After testing mosquitos on healthy birds, the researchers infected one bird in each pair with avian malaria and repeated the tests 10-13 days later, when the birds were sickest. Two weeks after that, they tested the mosquitos and birds a final time. By then, 9 birds had died. But the surviving infected birds had entered the "chronic" stage of infection, when the parasite lies low and the victim isn't as sick.

Mosquitos weren't any more interested in acutely ill birds than in healthy birds, the researchers found. This might have been because the malaria had driven down their red blood cell counts, making their blood less delicious to mosquitos. But once the canaries entered the chronic stage of malaria, mosquitos clearly preferred to feed on the infected birds. The authors report their findings in Ecology Letters.

Cornet believes malarial birds give off some signal to attract mosquitos, such as extra carbon dioxide or a specific odor. What exactly that signal is, and how the Plasmodium parasite manipulates its host into sending the signal, remains a mystery.

A canary is of course not a person, and their malaria parasites are different from ours as well. But there are similarities in how the two parasites act on their hosts, Cornet says. Humans, like birds, might give off some mosquito-enticing perfume when infected with malaria. Finding this perfume could help prevent malaria transmission in the future. And even before that happens, Cornet says, it's useful for people who model the spread of malaria to know that mosquitos aren't choosing their victims randomly.

If you're still feeling resentful toward mosquitos, it may help to know that the malaria "perfume" is really a trap. Mosquitos that carry Plasmodium parasites are about a third less fertile than they would be otherwise, another study this year found. Drinking from infected hosts is bad for mosquitos just like it's bad for the next animal they bite. But, like us, they're helpless to Plasmodium's wiles.


Cornet, S., Nicot, A., Rivero, A., & Gandon, S. (2012). Malaria infection increases bird attractiveness to uninfected mosquitoes Ecology Letters DOI: 10.1111/ele.12041

Image: Travis S. (Flickr)

The Shambulance: Copying Roger Clemens Won't Help You Lose Holiday Pounds

The Shambulance is an occasional series in which I try to find the truth about bogus or overhyped health products. With me at the wheel of the Shambulance are Steven Swoap and Daniel Lynch.

The injections he'd been receiving in the buttocks during his major-league baseball career, pitcher Roger Clemens explained to a jury this summer, were not steroids. They were perfectly legal and innocent shots of vitamin B12. The jury acquitted him, lifting the weight of a felony perjury charge from his shoulders. You, too, can use B12 to put some spring back into your step—at least, if you believe the companies that market the injections for weight loss, energy, and general well-being. In reality, this is not a performance enhancer.

B12 is a quirky vitamin that you can't get from plants. It's manufactured by bacteria that provide their services to some animals by living in their guts. Humans mainly get B12 from meat, eggs, and dairy. Of course, this means vegan humans have to find the vitamin elsewhere, such as in fortified breakfast cereals or Flintstones chewables. (They might also ingest B12 from soil bacteria on vegetables that haven't been washed well.)

"Healthy individuals have a six-year supply of B12 stored in their liver," says Daniel Lynch, a biochemist at Williams College. So even a temporary shortage in your diet shouldn't harm you. Long-term vegans, though, can become deficient in B12. Some older adults and gastric-bypass patients who can't absorb enough B12 from their food need to get it from an outside source. And patients who suffer from a disorder called (oddly) "pernicious anemia" need B12 supplements.

B12 deficiency causes weakness and fatigue, and an injection of the vitamin reverses those symptoms. This has apparently led some people to conclude that healthy, non-deficient folks will also get stronger and more energetic by taking B12. Why settle for normal functioning when you could be a vitamin-powered superhuman?

"[Weekly] vitamin B12 injections are intended to crank up the metabolism and boost energy levels to increase daily activity and help weight loss even when the body is at rest," says one Chicago weight-loss center.  An "anti-aging" clinic asserts that "B12 injections are...an effective means of boosting the body's metabolism for those looking to lose weight."

You'll start by shedding weight in the wallet region: a 3-month course of shots from that office will relieve you of nearly $500.

It's true that vitamin B12 is involved in metabolism. However, according to the National Institutes of Health, "Vitamin B12 supplementation appears to have no beneficial effect on performance in the absence of a nutritional deficit."

In other words? "Basically, for any healthy person this is a sham," Lynch says. "Any excess B12 is peed out anyway."

Non-human animals store B12 in the liver, just as humans do. "So you could get the same effect of the injection by munching on liver," says Steven Swoap, a physiologist who's also at Williams College. "This is how they 'cured' vitamin B12 deficiency a hundred years ago."

If you still feel a craving for B12 but don't care for liver sandwiches, you can buy bottles of B12 pills—and they'll run you about five cents a tablet. "It begs the question as to why anyone would stick a needle in themselves when you can buy this stuff as a pill at the local drugstore," Swoap says. Maybe we can find a Hall-of-Fame-nominated baseball player to explain it.

Image: Craig Strachan (Flickr)

Belly Button Safari: Who's Living in There?

"We are covered in an ecological wonderland," declares Rob Dunn, a man with a strange idea of a wonderland. In the wild bacterial jungle that is our skin, Dunn has been studying an especially dark cave: the belly button. He's found out which microorganisms are the big game, which are the rare birds, and which ones may take up residence in your navel if you stop bathing.

Dunn is a biologist at North Carolina State University who studies the tiny life forms that share our personal space, from insects in our yards and houses to microbes on our bodies. The organisms we live with can affect our health, for better or worse. Yet researchers are only beginning to explore the various ecosystems we carry on ourselves. From our intestines to our faces to the bottoms of our feet, each of us holds a planet's worth of different habitats.

Out of all these bacterial habitats, the belly button is especially convenient to study. Everyone has one. Its shape and size don't change dramatically from person to person (among innies, anyway). And it's hard to scrub clean, making it a relatively undisturbed environment on the body. A national park, if you will.

The belly button also has crowd appeal, which is important for Dunn's citizen-science approach. He's interested in projects that involve unsqueamish members of the public. For his belly button research, Dunn recruited crowds at two 2011 events: One was Darwin Day at the Museum of Natural Sciences in Raleigh, North Carolina, and the other was the annual Science Online conference in Raleigh.

In total, 60 volunteers had their navels swabbed. Researchers extracted the bacterial DNA from each sample, sequenced it, and searched it for matches to particular species.

What the team found was diversity, and lots of it, as they report today in PLOS ONE. With a median of 67 different bacterial species per person, Dunn says the navel is at least as diverse as the other skin areas studied so far. That diversity varied widely; some people housed more than 3 times as many species in their belly buttons as others.

Out of the thousands of bacterial species the researchers found overall, the vast majority showed up in only a few people, or in just one person. Even though this habitat looks similar from one person to the next, we all have very different collections of rare critters running around in the undergrowth. No one bacterial species appeared in every belly button.

But there are common belly button denizens, too. On our umbilical safari, these are big obvious trees and loud monkeys that show up in most people's jungles. Eight species of bacteria were present in more than 70% of subjects. And wherever these species show up, they do so in large numbers. If you could dump the bacteria from everyone's belly buttons into one pile, members of the 8 king-of-the-jungle species would make up nearly half the heap.

Extending this group to the 23 most common bacterial species, the researchers looked at how the group's DNA compared to rarer bacteria. They found that the ruling bacteria were more closely related to each other than randomly selected groups of bacteria were—sort of a royal family. This suggests that the most common belly button bacteria share evolved traits that help them thrive in this environment.

The most surprising thing about the belly button bacteria, Dunn says, is their ultimate predictability. Even though thousands of species turned up in his study, he now knows which ones are most likely to live in someone's navel. "I expected that the common species would be far more random," he says. "But the truth was otherwise." There are only a few bacteria ruling the belly button jungle, and a diverse throng of others that make up their subjects. Dunn thinks we might be able to study what goes on in our skin's ecosystem by focusing on these few common bacteria.

Dunn hopes that eventually he'll be able to predict the specific bacteria living in someone's belly button based on their age, gender, habits, and history. "But I'll admit we are having an interesting struggle," he says. The research shows that people can be sorted into two or three "bacteriotypes," like blood types, based on the clusters of bacteria that inhabit their navels. But as to why a person is one type or another? "So far we can't explain what causes those differences," Dunn says. "It is a real mystery."

He's getting a little help in this area from one Science Online participant who claimed not to have showered or bathed in "several years." This subject's belly button swab turned up two species of archaea—single-celled organisms, entirely separate from bacteria, that often live in extreme environments. Until now, no one had found archaea on human skin.

This social non-conformer might represent the kinds of bacteria that our ancestors carried around. "Historically, no one washed very often," Dunn says. "This colleague of yours may be far more representative of how our bodies were for thousands, or even millions, of years than are most folks."

He adds, "That isn't saying I'm encouraging everyone to abandon washing."

Dunn suspects that belly button depth, too, might influence what species live there. But he's had a hard time studying this. "No one really wants to answer a question about the depth of their innie, no matter how anonymous we make the process," he says. However, his group's next study will look at a larger group of people, including outies.

Future safaris into our bodies' ecosystems might help scientists understand skin allergies and other health issues. Although belly button sampling is over for now, Dunn encourages people who want to get involved to join the mailing list at yourwildlife.org. He's currently looking at camel crickets in basements, ants in yards, and bacteria in bedrooms and kitchens.

"Armpits," Dunn adds—or perhaps threatens—"are also on the horizon."


Jiri Hulcr, Andrew M. Latimer, Jessica B. Henley, Nina R. Rountree, Noah Fierer, Andrea Lucky, Margaret D. Lowman, & Robert R. Dunn (2012). A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, but Predictable PLOS ONE : 10.1371/journal.pone.0047712

Images: Copyright Belly Button Biodiversity.

The Shambulance: 5 Reasons Not to "Cleanse" Your Colon

The Shambulance is an occasional series in which I try to find the truth about bogus or overhyped health products. Physiologist Steven Swoap is with me at the helm.

If you've been tempted by promotions for "colon hydrotherapy"—that is, sessions in which you would pay someone to put a tube up your rectum and wash out your large intestine with water, like a dirty garage being hosed down in summer—then you've already overcome some impressive mental hurdles. Maybe you're almost ready to enjoy the relaxation, renewed energy, and improved health that the procedure promises. Before you take the plunge, as it were, here are a few points to consider.

It's not the 19th century.
People who offer colon hydrotherapy (also called a colonic) tell you the large intestine is full of "toxic waste and toxins." It does, of course, carry waste out of your body. But is it a two-way street?

"Intestinal autointoxication," the idea that poisons from your feces can move backward from your colon into the rest of your body, is an old one. Old as in ancient Egyptian. The Greeks were into it too, including Hippocrates and Galen.

In the 19th century, doctors prescribed laxative pills and enemas to cure all manner of illnesses. One man created and promoted a popular device called the Cascade. As alternative medicine researcher Edzard Ernst describes it, this was a rubber bottle with a nozzle for a person to insert into his or her rectum. When the person then sat on the bottle, it squirted 5 liters of fluid into up into the colon.

By the 1920s, though, some actual scientific study had been done on the subject. Unlike the Cascade, the theory of intestinal autointoxication did not hold water.

A toilet is not a gym.
"Having colonics is like taking your colon to the gym," declares the website for one colon hydrotherapy center. Filling the colon up with water and emptying it again, the theory goes, "exercises" the intestinal muscle so it can do its job better in the future.

"Injecting water into the colon will cause the colon to swell, and cause so-called 'stretch-activated' contractions of the smooth muscle surrounding the intestine," says Williams College physiologist Steven Swoap. These contractions are called peristalsis. "But the colon does this naturally as food stuffs pass through," he adds. "There is definitely no need to help this along for peristalsis to occur."

Colorectal surgeon Francis Seow-Choen points out in a review paper that since the colon is lined with smooth muscle (a type we can't voluntarily control), it cannot be toned like the muscles you work at the gym. Toned muscles are ones that we've consciously flexed so often, our brains learn to flex them automatically. Sit-ups work; water up the rectum doesn't.

It's rude to firehose your friends.
In addition to waste, your colon houses a large portion of your body's friendly bacteria. These gut microbes manufacture several vitamins we need, and seem to be involved in defending us from dangerous microorganisms and generally keeping us healthy.

One study found that cleaning the colon to prepare patients for a colonoscopy—in this case with a straightforward laxative, not with large volumes of pumped-in fluid as in a colonic—immediately altered the types of bacteria in patients' intestines. Another study found that cleaning out the colon both knocked down the bacterial population there and seemed to make it easier for new, potentially unfriendly bacterial strains to move in.

It might kill you.
"My biggest worry would be perforations caused by the water," Swoap says. "If abrasions or tears in the colon occur, you have the possibility of a dangerous bacterial infection." Ironically, one way to make the material in your colon as dangerous as colonic practitioners claim is to blast it with water. Breaking up the feces and creating tiny tears in the colon can turn a one-way street into a two-way hazard.

According to a paper in the Journal of Family Practice, reported complications from colon cleansing include cramping, abdominal pain, vomiting, rectal perforation, blood poisoning, kidney failure, fatal amoebic infection, and fatal accumulation of gas in the veins. Even if such a consequence is rare, Swoap points out, "it is sure not to happen if I don't let some technician put a hose in my rear."

Everybody poops.

Colons have been doing their job without outside intervention for hundreds of millions of years. "Your colon does not need help in a non-disease state," Swoap says. "Your colon is a pro!" If you want to thank it, step away from the hose and have some broccoli.

Image: Mykl Roventine

The Hazards of Being an Athletic Ape

This post first appeared at the Scientific American Guest Blog and is republished with permission.

With a single bad step as he ran untouched across a field this September, one of the best cornerbacks in the National Football League removed himself from the game for a whole season. New York Jets fans who saw Darrelle Revis’s left knee buckle under him that day may have pled with their televisions: not the ACL. But it was too late for Revis and his anterior cruciate ligament, which will undergo surgery this week.

Football fans are all too familiar with the ways in which a knee or ankle can fail a person. But athletes, like other humans, are simply doing the best that an ape running around on two legs can.

Before we lived and walked on the ground, our ancestors inhabited the tree branches. They didn’t look quite like chimpanzees or any other modern animal, but they were large apes built for climbing. They had big, grasping toes and extremely flexible feet and ankles. “These things were just brilliantly adapted for living in the trees,” says Boston University anthropologist Jeremy DeSilva. He studies the evolution of ape and human locomotion by looking at both ancient fossils and modern-day animals in motion.

When our ancestors descended from the trees and began walking upright, they faced some major mechanical challenges. “Being on two limbs is just a real problem,” DeSilva says. “If you were taking shop class and your assignment was to build a chair, and you built a chair with two legs, you’d fail the class because it would fall over all the time.” Simply balancing an animal upright is a feat of evolutionary engineering—and that’s before the animal starts moving around.

To walk on two limbs, our ancestors had to make several modifications to the feet they’d inherited from tree-climbing apes. Flexible, grasping appendages with 26 individual bones had to become stable surfaces that we could push off of with each step. “We’ve stiffened things up by patching these bones together with a bunch of ligaments that make up the arch,” DeSilva says. And muscles that were once used for grasping branches now support the foot’s arch. “But boy,” he says, “these are just a bunch of band-aids.”

Though these new two-legged bodies worked well enough to keep our lineage alive, bipedalism may not be the best idea evolution has ever had. “If you look across the animal world,” DeSilva says, “good ways of moving evolved multiple times.” Flight, for example, has evolved many times. So has a streamlined body in swimming animals. But striding on two legs evolved just once in mammals.

The only other animals that walk like we do are birds. And with a couple hundred million years to work on the problem, rather than the mere 5 million or so that we’ve had, birds have come up with what DeSilva thinks is a tidy solution: they’ve fused several bones together to create rigid, immobile feet.

In humans, DeSilva says, “I find the foot to be incredibly problematic.” He thinks a lifetime of walking and running on feet held together by evolutionary band-aids is bound to lead to the kinds of problems people frequently experience: plantar fasciitis, collapsed arches, shin splints, Achilles pain.

What’s more, DeSilva says, “We have evidence that these things are not just modern problems.” In the ancient hominins whose fossils he studies, there are many who suffered from the same injuries that plague us. There are broken ankles in individuals 1.9 and 3.4 million years old (both healed). There’s osteoarthritis in a creature that may have been Homo habilis. An Australopithecus has what looks like a compression fracture in its heel. Another individual sustained, and healed from, a severe high ankle sprain 1.8 million years ago.

Modern-day humans know a thing or two about twisted ankles. The most commonly sprained ligament in the whole human body is a tiny one in the ankle called the anterior talofibular ligament. What’s notable about this ligament, DeSilva says, is that almost none of our living ape relatives has it.

DeSilva’s opinion is that humans evolved this ligament to keep the ankle stable. An upright human is like a balanced stack of blocks, he says. Our ankle bones have flattened surfaces that sit on top of each other, unlike the curved and snugly fitted ankle bones of a chimp. When a human steps on an unexpected rock, this extra ligament in the ankle might be necessary to keep the whole stack of blocks from slipping off its foundation. We don’t dislocate a foot entirely when we trip on a curb—but we might be benched for a couple of months.

Like our ankles, our knees have wide, flattened surfaces that spread out the weight we’re carrying on two limbs instead of four. And they’re large, compared to our body size. “The whole bed-of-nails idea is at work here,” DeSilva says. “Human joints tend to be very puffy.” Structurally, though, our knees are similar to those of our climbing relatives; they have all the same components that a modern chimp’s knee does.

But chimps don’t ever land funny after a layup shot, or change direction too sharply while cutting upfield. That kind of sudden sideways motion is the knee’s downfall, and can rip or snap the ligaments that stabilize the joint.

The infamous ACL sits inside the front of the knee joint, holding the thigh bone in place on top of the shin bone. Its counterpart at the back of the knee is the posterior cruciate ligament. The MCL and LCL, or medial and lateral collateral ligaments, cradle the knee joint on either side and are especially vulnerable to sideways jarring. Too much twisting in the knee can tear the menisci, pads of cartilage tucked inside the knee socket.

Our knees have no problem with the normal folding and straightening of our legs. “When you go too far out of range in the other directions, that’s when you get in trouble,” says Irene Davis.

Davis is a physical therapist and biomechanics researcher at the Spaulding National Running Center at Harvard University Medical School. Despite how often we suffer injuries, Davis says, “I think we’re designed really well for both walking and running.”

Davis cites the theory, promoted by Harvard anthropologist Daniel Lieberman and others, that early humans evolved as so-called persistence hunters. Before they developed effective spears, the theory goes, our ancestors obtained meat by separating an animal from its herd and simply chasing it on foot until it couldn’t run any farther. Researchers point to various skeletal features and cooling mechanisms—and the fact that some people seem to enjoy it so much—as evidence that our species is built for long-distance running.

Of course, early humans would have done it without Reeboks on. In the clinic, Davis advocates what she calls a more natural style of running. She teaches people to land gently on the front of their foot with each step, as barefoot runners do, rather than hard on their heels as people with cushioned running shoes tend to.

Davis believes that wearing structured, arch-supporting shoes makes feet weak and lazy, and that this weakness leads to common foot injuries such as plantar fasciitis. Yet feet are largely ignored until they give us trouble. “You don’t see people at the gym strengthening their feet,” she says, but you should. “Strong feet are healthy feet.”

Despite what DeSilva sees as evolutionary patchwork, Davis thinks the human foot is “just a fantastic structure.” Each time the foot hits the ground, it must be both flexible enough to absorb shock and adjust to uneven terrain and rigid enough to push off of again. Davis thinks the problems come when we don’t use our feet and legs as evolution intended.

When treating patients with overuse injuries, Davis teaches them to run with better mechanics so they avoid getting the same injury in the future. Runners receive feedback on their motion from tools such as accelerometers or mirrors, then practice carrying their bodies in better alignment.

Davis says people can also be taught to prevent future acute injuries such as ACL tears. Most ACL injuries are non-contact; as Darrelle Revis knows, one awkward step is all it takes. So there are programs that teach athletes to land their jumps more gently, or aim to strengthen stabilizing muscles around the knee to protect its ligaments. Though some people will still choose to put themselves in the paths of linebackers, they can at least learn ways to run and jump that put less strain on their vulnerable ligaments to start with.

Having recovered from recent injuries of his own, Jeremy DeSilva will be lacing up his minimalist Nike Free sneakers to run a marathon this weekend. Influenced by the research on barefoot running, he’s left cushioned sneakers behind and is now propelling himself more like his Australopithecus subjects did. “I guess I take my work home with me,” he says.

Davis runs completely barefoot, though in the winter or when she needs more protection for her feet she’ll wear a minimal covering such as water shoes. She also rollerblades.

One sport Davis doesn’t enjoy is football. “I don’t like watching the injuries,” she says. “I see a big pile of people with someone underneath it and it just drives me crazy.”


Image credit: Cpl. Michelle M. Dickson