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

Hack Your Workout: These Songs Make People Take Bigger Steps

Do you have a workout playlist? You may find yourself matching the stride of your power walk to the beat in your earbuds—but tempo isn't the only thing affecting how fast you go. Certain musical pieces seem to make people take longer strides, even while walking to the same beat. (Spoiler alert: Aqua.)

Marc Leman is a musicologist at Ghent University in Belgium. With his colleagues, he created a list of 52 songs with a tempo of 130 beats per minute, a speed they chose based on previous research. The playlist included a variety of genres, and all the songs were in 4/4 time.

Then the researchers gathered 18 "normally built" adults, strapped sensors to their legs, and sent them walking laps around a gymnasium. The subjects were explicitly told to walk in time to the beat of the music. Through headphones, they heard 30-second clips of the different songs, with periodic interludes of only a metronome sound.

Although all the music had the same tempo of 130 beats per minute—which subjects stepped in time with—their actual walking speed varied as they took longer or shorter strides. Leman says that to certain songs, people walked 10 percent faster than they did to others (or to the metronome beat).

The researchers dubbed the fastest-walking songs "activating," and the songs that made people walk slowest "relaxing." The full playlist is here, ranked from most relaxing to most activating. These were the top 10 most relaxing songs, to which walkers made the least forward progress:

And here are the tunes to which people covered the most ground:

Right around the middle was "Dragostea din tei," better known by some as "the Numa Numa song." Test subjects probably got slowed down by the requisite arm flailing.

Separately, the researchers asked subjects to rate the musical selections on a variety of adjectives: Was the song happy or sad? Tender or aggressive? Known or unknown to the listener?

Some of the responses were tied to how speedily the songs made them walk. For example, pieces described as "stuttering" rather than "flowing" made people take shorter strides. Pieces that subjects found especially "aggressive" or "loud" (although the volumes of all the songs had been matched in their headphones) made people walk faster. So did songs they described as "bad" rather than "good." (This may explain "Barbie Girl").

The musicologists, meanwhile, tried to find more scientific explanations for the powers of certain songs. Leman says this was surprisingly difficult. They did find that more activating songs tended to have simpler melodies, with fewer notes per beat. These pieces often had a strong bass line, as well as clear downbeats ("one two three four..."). The group is still working on figuring out what kinds of music make people move the fastest.

For his own exercise playlist, Leman is a fan of jazz, though he says it's not always great at getting a person moving. He thinks syncopation, which interrupts the regular beat of the music, is an important factor in making a piece relaxing rather than activating. Instead of marching straight ahead, syncopated jazz music seems to encourage you to walk with more horizontal motion, Leman says: "You want to swing."


Image: by Malingering (via Flickr)

Marc Leman, Dirk Moelants, Matthias Varewyck, Frederik Styns, Leon van Noorden, & Jean-Pierre Martens (2013). Activating and Relaxing Music Entrains the Speed of Beat Synchronized Walking PLOS ONE DOI: 10.1371/journal.pone.0067932

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

The Shambulance: Deer Antlers Are Not Unicorn Horns

The Shambulance is an occasional series in which I try to find the truth about bogus or overhyped health products. The chief navigational officer of the Shambulance today is Steven Swoap.

This Superbowl season saw a star linebacker forcefully denying that he'd ever sprayed juice made from ground-up deer antlers into his mouth. The player was Ray Lewis, and using deer antler spray would have seemingly violated the National Football League's ban on performance-enhancing drugs. Like the horn of a unicorn, this product is alleged to heal and strengthen its users. Also like the unicorn horn, it's probably not something the NFL needs to worry about.

Bottles of deer antler spray—also called deer antler velvet or IGF-1 spray—are legal and easy to purchase for $20 to $50. Though no one's checking what's actually inside the bottles, makers claim their products come from antlers that are harmlessly sawed off of male deer each spring, or from the soft skin covering these new antlers. A few times a day, you spritz the solution into your mouth and swallow it.

The suggestion is that deer antler spray will make your own muscles or bones regrow as rapidly as a deer's antlers. Some products make other claims that are variously expansive, including weight loss, better endurance, a boosted immune system, and higher sex drive. Fueling all these promises is a hormone called IGF-1 (short for insulin-like growth factor). Like medieval "unicorn horns" that were really the tusks of narwhals, IGF-1 is less glamorous in reality than in legend.

It's true that deer antlers "grow like crazy," says Steven Swoap, a physiologist at Williams College. "There are not many examples where a tissue grows faster than an antler. Except for maybe some pumpkins."

We humans are naturally curious about tapping into that growing power. And IGF-1 is certainly involved in growth. In humans as well as deer, it's mostly manufactured by the liver. We make more of it during growth spurts, Swoap says. Producing too much IGF-1 is linked to certain cancers—growth that can't be stopped.

"Does IGF-1 cause antler growth? It is possible," Swoap says. "A more likely candidate is testosterone." Female deer, which also make IGF-1, don't grow antlers; male deer have extra testosterone in their bodies during the antler-growing season. "There are likely many factors involved," Swoap says.

Whatever ingredient gives deer antlers their seemingly magical growing power, we aren't likely to capture much of it by grinding up the antlers themselves. "The antler is not a hormone producing factory," Swoap says. Antler growth is triggered by hormones sent from elsewhere in the body, such as the liver, thyroid, or testes. ("You would be much better off making a spray out of the testes of deer," Swoap suggests. "Or you could perhaps get the IGF-1 from the liver, where it is made, and have a liver milkshake with your deer nut spray.")

Even if a useful quantity of IGF-1 made it out of the antlers and into the spray, the molecule would have a hard time completing its journey into the hopeful athlete's body. Swoap says IGF-1 is a hefty protein that's unlikely to slip into your bloodstream through the soft tissues under your tongue. And once swallowed, it would break down in your digestive tract.

Swoap compares IGF-1 to another famous protein hormone: insulin. "For years, we had to inject it, and it is only recent technological advances that allowed us to deliver it subcutaneously," he says. "To say that the technology is replicated in a bottled spray is ridiculous."

Mitch Ross, the owner of the company that claimed Ray Lewis used its deer spray to recover from an injury, calls his products "technologies that are light years ahead of what people can understand." In other words, even if we can't explain the science, we should accept that deer antler extract helps people.

Except that it doesn't.

Researchers have given oral deer antler supplements to various groups of people, compared them with placebos, and looked for any effect. Men who took deer antler supplements during a strength training program showed no change in hormone levels (including IGF-1) and no difference in aerobic endurance. Rowers also showed no change in hormone levels and no difference in strength or endurance. (As for those other claims, a study in middle-aged men found no increase in sexual function.) A review paper last year concluded there is no convincing evidence that deer antler extract is useful to athletes.

It seems we haven't yet lopped anything special off the heads of those deer. Ray Lewis and (because even athletes who compete at a walk apparently want performance boosters) golfer Vijay Singh are busy defending their reputations against deer antler spray. Yet the product wouldn't have given them any extra powers except a placebo spritz of confidence. Professional sports organizations have plenty of real beasts to chase down in the world of banned substances, but this one is only a mythical creature.


Image: skipnclick (Flickr)

Why Humans Prefer Not to Gallop

As kids, we discover that our two legs can manage many different gaits. After walking and running we figure out how to tiptoe, hop, and skip. (Personally, I decided at one point to become a better skipper than anyone I knew, practicing backward skipping and figure-eights in our driveway. I may have sensed that my competition in this pursuit was not very stiff.)

For basic getting around, we usually settle on walking and running. But why do we ignore so much of our bipedal repertoire in favor of locomotion that's more, well, pedestrian? Researchers in Belgium asked this question about one gait in particular: the gallop.

In case you missed this one as a kid, the human version of a gallop involves holding one leg always in front of the body and the other leg always behind. Bounding along, you create an uneven rhythm of footfalls: ba-DUM, ba-DUM, ba-DUM.

"Gallop is, though rarely used, a familiar gait for humans," the authors write in the Journal of Experimental Biology. People may start galloping spontaneously under certain (infrequent) circumstances, such as going quickly downhill.

For their study, lead author Pieter Fiers of the University of Antwerp and his colleagues had a dozen volunteers run and gallop down a hallway, then dissected their motion in great detail. Platforms that lined the hallway measured the force people produced in their steps. The subjects were covered in motion-capture markers, like Avatar actors. Finally, a separate group of subjects did their running and galloping on a treadmill while the researchers measured how much oxygen they used and carbon dioxide they gave off.

People preferred to gallop at pretty much the same speed they ran. But the length of a galloping stride was shorter than a running stride—so gallopers had to take more steps, and do more work, to travel at the same speed as runners.

Gallopers exerted that effort unevenly, with the front leg doing more work than the back leg. And the galloping stride, researchers saw, demanded more from the hips than running did. This tired people out quickly. Out of 12 treadmill gallopers in the study, 4 gave up before the end of their 4-minute session, complaining of fatigue and stress in their hips and thighs. (An intended 13th galloper couldn't figure out how to gallop on the treadmill belt in the first place.)

When researchers calculated their subjects' metabolic rates, they found that galloping was about 24% more costly than running at the same speed. In other words, galloping burns up more energy, takes more effort, and is less comfortable than running. It's no wonder we don't usually opt for it.

Still, the fact that we're not efficient at galloping means it would be a tougher workout than running. Maybe athletes should start mixing some alternative gaits into their usual exercise routines. Who knows—with practice, you might become the best galloper in the whole world.


Fiers P, De Clercq D, Segers V, & Aerts P (2012). Biomechanics of human bipedal gallop: asymmetry dictates leg functions. The Journal of experimental biology PMID: 23239890

Image: Devon D'Ewart (Flickr)

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.

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

The Shambulance: Ab Toning Belts (or, Muscle Tone Is All in Your Head)

(The Shambulance is an occasional series in which I try to convince you not to spend your money on bogus health products. Helping me steer the Shambulance is Steven Swoap, a biology professor and physiology expert at Williams College.)

Did you ever wish you could torture your midsection with electricity until it broke down and produced a six-pack, like a prisoner of war giving up state secrets? You might want a battery-powered toning ab belt. If you don't have time for crunches, it will crunch your abdominal muscles for you: on your couch, at the grocery store, in PTA meetings, or anyplace you can wear it under your shirt and aren't worried about people noticing the flinching.

The makers of one toning belt line claim that their "Electrical Muscle Stimulation (EMS) toning technology...works to mimic the body's natural muscle movements." Electrical signals travel between gel pads inside the belt, "switching on the nerves that control your muscles and causing them to contract naturally." 

It's recommended that you use the belt 4 to 5 times a week, in 30-minute segments, cranking up the intensity level each time to the highest you're comfortable with. After 4 to 8 weeks, you'll notice stronger and more toned abs. Not bad for $100 or $150 and zero bicycle sit-ups. If you've been wearing the belt to work, you may also have been let go thanks to your constant grimacing. Use your newfound free time to take that body to the beach! 

After your abdominal success, you may be interested in refining your other problem areas too. If so, you can buy toning straps for your arms, shorts for your butt, or a creepy headset for your face muscles. (Available in the UK for 250 pounds. Anti-aging results in just 12 weeks!)

"There are two major problems with devices like these," says physiologist Steven Swoap. Or three, if you believe customer reviews about how difficult the padded shorts are to put on.

The first problem is that stimulation like this probably cannot make your muscles any stronger. "These devices tend to only activate the surface of the muscle," Swoap says. The electricity causes tingly-feeling contractions around your middle, but it doesn't reach deep. To entirely activate the abdominal muscles, "You would either need to have a massive voltage from the surface (burning skin, anyone?) or surgically implanted electrodes."

The second catch is that even if this device did make your muscles stronger, you wouldn't be able to see the results. 

A "toned" muscle, Swoap says, is really a muscle that you're flexing all the time without trying. "By doing a zillion sit-ups a day, you train your nervous system to activate your abs, even when you are not thinking about it." Once you've trained your brain well enough, it will start contracting those muscles into a washboard shape automatically. 

To make muscles grow larger, and not just more toned, takes resistance exercise such as heavy weight lifting. But even big, strong muscles will look flabby and droopy unless your brain is sending the signal to activate them. The toning belt, though, goes straight to the target muscle without talking to your head. "Muscle zappers like this don't train your brain at all," Swoap says.

Not to mention that if you're relying on the belt to trim your waist, rather than exercising and watching your diet, you'll still be saddled with whatever fat was there before. You might have abs of steel, but they'll be hidden under a cozy layer of cushioning. Maybe you can prove it to your beach buddies with a plank contest.

If you really want to make your muscles more defined, the answer—sadly enough—is that you've got to do it yourself. Whether it's your abs, arms, butt, or something else, "The only way to be 'toned' is to repeat the exercise over and over and train your brain," Swoap says. 

Facial crunches, though, might be a whole different kind of torture.

Images: Slendertone US; Slendertone UK

How to Slim Down, Manage Your Man, and Stay Tight with Your Girlfriends!

Who ever said science wasn't for us ladies? This week's research is full of tips on looking good, eating right, and taking care of your man! Plus: Don't miss a shocking true story about a girls' get-together turned deadly.


DIET
The calorie-free way to de-bland your diet

You try to eat right. But sometimes that low-sodium poached chicken breast on lettuce doesn't thrill your taste buds. What if merely looking at pictures of steak, pizza or pastries made your healthy meal taste heartier? New research from Switzerland says that just might work.

A group of Swiss scientists studied 14 healthy adults. The subjects held an electrode on their tongues while researchers flashed pictures of foods in front of them. The electrode gave off little buzzes of "electric taste," triggering subjects' taste buds with a neutral, slightly metallic taste.

People experienced a more pleasant flavor in their mouths when the electric taste was paired with a high-calorie food picture than a low-calorie one. The scientists say these images of forbidden foods light up the parts of our brains that go "Mmm!"

Could you try this trick in your own home? The researchers didn't study what happened when people ate actual food while looking at pictures. But if your gluten-free, high-fiber bread is blander than a piece of metal, staring at a picture of chocolate cake might make it seem tastier.


FITNESS
This surprising workout trick will have you handing back unwanted pounds!

If you're overweight, you might find exercise frustrating. Just a few minutes of exertion can leave you feeling overheated and sweaty. But research presented at an American Heart Association meeting may provide a solution to your problem: colder hands.

Researchers at Stanford University conducted a small study on obese women between the ages of 30 and 45. All the women participated in a 12-week exercise program that included push-ups, lunges, and using a treadmill. Half the women held their hands in cylinders of cold water while they were on the treadmill, while the other half kept their hands in body-temperature water.

Because the women who exercised with their hands in cold water stayed cool, they were less likely to get frustrated and drop out of the exercise program. (They even stuck it out through those dreaded push-ups!) These women lost more weight and got in better shape than the other group of women.

You probably don't have one of these cold-water exercise devices in your local gym. But you can still apply the findings to your own exercise routine. In the summer, why not freeze water bottles and hold them in your hands while you work out? And in colder months, get outside and ditch those gloves! After all, everyone can agree that a beach-ready body is worth a little numbness in the extremities.


MAN MANUAL
Are cheeseburgers turning your guy's swimmers into toast?

Bad news, drive-through lovers! Fertility specialist Jill Attaman says a diet high in saturated fat is bad for sperm counts.

Attaman studied the swimmers of 99 men who came to a fertility clinic. She also gathered data about the men's diets and divided them into three groups based on their fat intake. The men in the highest fat-consuming group had sperm counts 43 percent lower than men who consumed the least fat. That's news that will chill some men's hearts colder than a Shamrock Shake.

But it's not all bad news for fats. While saturated fats were tied to low sperm counts, healthy fats called omega-3's seem to be good for sperm. Men who were in the highest third for consumption of this kind of fat had healthier, better-formed swimmers. So next time you cook your burger king a thoughtful dinner, think of his own little sesame seeds and try salmon instead of steak.


TRUE LIFE READ
"I was part of a hot defensive bee ball"

Bertha,* a Japanese honeybee, was hard at work in her hive one day when she became aware of an intruder. A giant hornet, Vespa mandarinia japonica, was inside the entrance of the hive. Suddenly Bertha found herself swept up in a buzzing mass of bodies.

"I'd heard rumors about the hot defensive bee ball before," Bertha says, "but I'd never been a part of one myself." The sister honeybees clumped together in a tight swarm around the massive body of the hornet. (They don't call them giants for nothing. Check out some mug shots of these unpopular predators here.)

Vibrating their muscles to generate heat, the bees cranked the temperature in the swarm up to 46 degrees Celsius, or 115 degrees Fahrenheit. That's even hotter than your Bikram class! It was uncomfortable for Bertha--but for the hornet, it was worse.

Within an hour, the hornet was dead. The bees dispersed. And that's when they found themselves, instead of at the hive's entrance, inside a glass beaker. The attack had all been a ruse perpetrated by scientists. The hornet hadn't even been coming after the bees in earnest; researchers had shoved it inside the hive on a wire.

"I felt sort of used," Bertha says. "I was just swept up in the moment, and now I know I was manipulated into joining the bee ball. But at least it was for science." (Bertha was luckier than some of her sisters, who were forced to donate their heads to science as well.)

The researchers wanted to find out what genes were activated in bees' brains while they formed the hot defensive bee ball. They found one gene of note. But the same gene was active when bees were heated up outside of the bee ball. So it seems to be a response to the furnace-like environment the bees create, not a cause of the mysterious ball-forming impulse.

To find out what drives bees to form hot, deadly mobs in the first place, scientists--and Bertha--will have to wait.

*Some names have been changed.


Ohla, K., Toepel, U., le Coutre, J., & Hudry, J. (2012). Visual-Gustatory Interaction: Orbitofrontal and Insular Cortices Mediate the Effect of High-Calorie Visual Food Cues on Taste Pleasantness PLoS ONE, 7 (3) DOI: 10.1371/journal.pone.0032434 


Attaman, J., Toth, T., Furtado, J., Campos, H., Hauser, R., & Chavarro, J. (2012). Dietary fat and semen quality among men attending a fertility clinic Human Reproduction DOI: 10.1093/humrep/des065


Ugajin, A., Kiya, T., Kunieda, T., Ono, M., Yoshida, T., & Kubo, T. (2012). Detection of Neural Activity in the Brains of Japanese Honeybee Workers during the Formation of a “Hot Defensive Bee Ball” PLoS ONE, 7 (3) DOI: 10.1371/journal.pone.0032902 


Images: plates of food Ohla et al.; glove peanutian/Flickr; burger guy Mr. T. in DC/Flickr; bee klugi/Flickr

It's Harder to Dodge Sharks When Pregnant

Although it would be nice to hatch our babies from eggs Anne Geddes-style, or deliver them while still tiny and carry them around in a pouch, humans and other placental mammals are stuck lugging their developing fetuses inside their bodies. Luckily, most humans aren't in danger of predation. But for animals that sometimes have to run (or swim) for their lives, pregnancy can be dangerous.

In a punnily titled new study ("Pregnancy is a drag"), UC Santa Cruz researcher Shawn Noren investigates how pregnant dolphins are affected by carrying a wide load. Noren studied two captive bottlenose dolphins, each about 10 days away from giving birth, living in a lagoon in Hawaii.

Though the study only included these two dolphins, Noren collected many data points by having a scuba diver sit underwater and videotape the dolphins swimming back and forth. The dolphins were also observed and recorded periodically during the two years after they gave birth. By digitizing these videos, the researchers could quantify the dolphins' size, mass, surface area, swimming speed, and swimming mechanics.

As expected, very pregnant dolphins had a very much larger surface area. This created greater drag as the dolphins glided through the water. The dolphins also changed their swimming "gait," like a human who finds herself a little waddle-y in the final trimester. Dolphins get all their forward thrust from the up-and-down beats of their tails. The pregnant dolphins beat their tails a little more shallowly than usual, maybe because their muscles were stretched out and weakened by the fetus (or because their midsections were less flexible). Just like a human taking smaller steps, a dolphin making smaller tail-beats covers less distance. So the pregnant dolphins had to beat their tails faster to maintain a given speed.

Besides experiencing greater drag and a shortened "stride," pregnant dolphins have altered blood flow and lower lung capacity. They also store more lipid (fat) than usual in their blubber, making them extra buoyant. All these factors combine to slow a dolphin way, way down. The two pregnant dolphins in the study swam more than 60% slower, on average, before their calves were born. After recovering from pregnancy, the dolphins' average swimming speed was around 9 mph. But before giving birth, their speed was closer to 3.5 mph--similar to the pace of a walking human.

The crucial factor in avoiding predators such as sharks, though, is maximum speed. After pregnancy, the dolphins reached maximum swimming speeds of more than 14 mph. While heavily pregnant, they barely reached 8 mph. Of course, the researchers didn't introduce any sharks or killer whales into the lagoon to see how fast the dolphins could swim under real duress. But the researchers note that at the fastest swimming speeds they observed, pregnant dolphins would not have been able to out-swim most predators.

It's unknown whether pregnant dolphins are more vulnerable to predators in the wild. But among ungulates--hoofed mammals such as buffalo or wildebeest, which happen to be close relatives of whales and dolphins--pregnancy is a known risk factor for being eaten by lions. In dolphins, the greater effort needed to swim while pregnant probably means they need to take in more calories. But it also must make hunting for food more difficult. A pregnant dolphin will have a harder time chasing after quick prey or, because of her increased buoyancy, diving to hunt.

In humans, studies of how pregnancy affects walking have been inconclusive. This might be because there's a great deal of variation in how individuals' bodies adjust to pregnancy. These two dolphins, too, may not be representative of their whole species. But they demonstrate the amazing adaptability of a female mammal's body, whether she's diving for squid or just shuffling through the suburbs.

Image: Shawn Noren/JEB

Noren, S., Redfern, J., & Edwards, E. (2011). Pregnancy is a drag: hydrodynamics, kinematics and performance in pre- and post-parturition bottlenose dolphins (Tursiops truncatus) Journal of Experimental Biology, 214 (24), 4151-4159 DOI: 10.1242/jeb.059121

Exercise and Your Immune System Revisited

It's not every day I get an email from someone in Taiwan about exercise, white blood cells, and menstruation. But in response to my post How Much Exercise Harms Your Immune System?, Guan-Da Syu from National Cheng Kung University Medical College dropped me a friendly note (if you can call an email with its own bibliography a "note") a few days ago. Syu is the lead author of the paper I'd discussed in that post, and he wanted to respond to some questions I raised.

The paper reported that after out-of-shape individuals engaged in sudden and intense exercise, their white blood cells died at an accelerated rate. An increase in reactive, oxygen-containing molecules seemed to be the culprit. But when those same people got consistent and moderate exercise--five days a week for 30 minutes--their white blood cells lived for longer. Furthermore, consistent exercise buffered the harmful effects of more strenuous exercise sessions on white blood cells.

I had asked whether we could be sure that shortening or increasing the life span of white blood cells (specifically, neutrophils) had a net negative or positive effect on individuals' immune systems. Might the body compensate somehow? Syu says that it's hard to quantify a person's immunity, but his findings fit with other research that linked extreme exercise with higher infection risk. Additionally, he says that after severe exercise, it takes about a half a day for the proportion of healthy white blood cells in the body to return to normal.

The consistent exercisers, Syu says, adapt to the oxidizing molecules, and begin to produce neutrophils that live for longer. I had asked whether prolonging the lifespan of short-lived cells might be a burden on the body somehow, but Syu points out that the number of neutrophils living in the body at one time remains the same throughout subjects' exercising or sedentary weeks. We don't have more white blood cells when we're in shape; we are able to produce fewer because they live for longer.

Finally, I'd pointed out that since the study only used male subjects, it's hard to generalize the results for woman, whose bodies don't necessarily react to exercise in the same way. Syu acknowledges that it's unknown how exercise affects women's white blood cells. But it's possible that the effect might depend on the time of the month. In a previous study, the same research group looked at women's platelets (the blood cells responsible for clotting). In the first half of the menstrual cycle, extreme exercise had a notable effect on platelet function. But in the second half of the cycle (from ovulation to menstruation), women's platelets didn't respond to severe exercise in any way.

So the effect of exercise on your immune system might depend on many factors: how hard you work out; how consistently you work out; whether you're a woman and what time of the month it is. It seems that consistent exercise protects your immune system, but going from zero to 60 when you start a workout routine is harmful. And women, for now, will remain a mystery.



Syu, G., Chen, H., & Jen, C. (2011). Severe Exercise and Exercise Training Exert Opposite Effects on Human Neutrophil Apoptosis via Altering the Redox Status PLoS ONE, 6 (9) DOI: 10.1371/journal.pone.0024385

How Much Exercise Harms Your Immune System?

I'm looking at you, marathoners and triathletes. While you're out there building superhuman endurance and making the rest of us feel bad, are you also beefing up your immune systems? Or does becoming an Ironwoman actually weaken your body's defenses?

It may depend on how you're exercising. Researchers in Taiwan compared two types of exercise, the names of which might reveal the researchers' own feelings toward hitting the gym: "Acute Severe Exercise" (ASE) and "Chronic Moderate Exercise" (CME). In medicine, "acute" is something that comes on quickly and is over soon, as opposed to a chronic illness. The flu, say, as opposed to mono.

The subjects were 13 males between the ages of 20 and 24. Though young and otherwise healthy, they weren't in shape; the subjects had been getting less than one hour a week of exercise for at least the past six months. At the beginning of the study, all 13 subjects underwent "acute" exercise, cycling at increasing levels of difficulty until they reached exhaustion.

Afterward, five subjects became controls. They were told to continue not exercising for the next four months. Twice during that period, they showed up for another bout of ASE, so researchers could make sure that their bodies and their exercise abilities were staying the same. Meanwhile, the other eight subjects began two months of "chronic" exercise. They worked out five days a week for 30 minutes. The moderate intensity of their workout was defined as a percentage of the work they'd been able to do during ASE. After two months, the exercisers were also instructed to stop exercising. They spent two more months getting no exercise at all. In each month of the study, they also did an ASE test so researchers could see how their bodies' response to severe exercise was changing.

Outwardly, the effect of consistent (excuse me, chronic) exercise on the bodies of formerly sedentary people was unsurprising. After two months of training, the CME subjects had lost weight, lowered their resting heart rates, and increased their endurance. Then they stopped exercising. After the two-month "detraining" period, subjects' weights and heart rates had returned to their original levels, though the work they could do in the ASE task was still elevated, showing a lasting effect on their fitness. The control subjects did their job well, staying the same during the four months.

But what the researchers were interested in was the inner changes in their subjects; namely, changes to white blood cells called neutrophils. These are key players in the immune system, responding to the site of infection in the body and attacking any invaders they find. Neutrophils are short-lived cells, committing cell suicide (called apoptosis) after only a few days in the bloodstream. If these white blood cells are too enthusiastic about offing themselves, it can weaken the immune system.

Neutrophil death may be linked to the abundance of oxygen-containing molecules that react with everything around them, harming structures inside the cell. Since extreme exercise can increase the amount of these harmful "reactive oxygen species" in the body's tissues, the researchers wanted to know how exercise affected neutrophils. They drew blood from their subjects periodically, both at rest and after their ASE trials, and removed the neutrophils for analysis.

They found that "acute severe exercise" did, in fact, accelerate neutrophil suicide. It also increased the amount of reactive, oxygen-containing molecules in the cells.

"Chronic moderate exercise," on the other hand, appeared to slow down the death of neutrophils. After two months of regular exercise, subjects' white blood cells were showing less oxidative stress and slower apoptosis. Even after subjects spent the following two months not exercising, the effect lingered.

In a final twist, the positive effects of consistent exercise seemed to counteract the harmful effects of extreme exercise. After the acute exercise task, subjects who'd been exercising regularly did not show the same damage to their neutrophils that they had at first. But after two sedentary months, the protective effect had begun to fade.

What does all this mean for the marathoner or the Ironwoman? Unfortunately, since the subjects were all men, the study says very little about women of any kind. But for the young, previously sedentary males involved, the study suggests that sudden, exhausting exercise accelerates the death of certain immune cells. Consistent and moderate exercise, on the other hand, prolongs these cells' lives. It also buffers the damaging effect of occasional extreme exercise. And when you stop exercising, the positive effects of your old routine linger, at least for a little while.

The researchers point to other studies that have shown a connection between sudden, extreme exercise and upper respiratory tract infections. In this study, we can't see the effect that various rates of neutrophil death had on subjects' immune systems as a whole. When neutrophil death was accelerated after acute exercise, were subjects truly more vulnerable to infection, or did the immune system compensate somehow for neutrophil loss? In subjects who got regular exercise and prolonged the lives of their neutrophils, was the immune system strengthened? Does keeping these short-lived cells alive for longer necessarily help prevent infection, or could it create a burden for the body?

Overall, the authors think the evidence is in favor of consistent and moderate exercise. For patients whose immune systems are impaired by HIV or chemotherapy, regular exercise might provide a boost. This study suggested that consistent exercise counteracts the negative effects of extreme exercise--at least some of the effects. But to stay on the safe side, the authors recommend that you avoid "acute severe exercise" like, well, the plague.


Syu, G., Chen, H., & Jen, C. (2011). Severe Exercise and Exercise Training Exert Opposite Effects on Human Neutrophil Apoptosis via Altering the Redox Status PLoS ONE, 6 (9) DOI: 10.1371/journal.pone.0024385

What Marathoner Mice Can Teach Us

If someone left a treadmill in your living room, how far would you run every day just because you felt like you had some energy to burn? Five miles? Zero miles, and you'd use it as a tie rack? How about 65 miles?

Researchers at the University of Pennsylvania and elsewhere studied mutant mice that were missing a particular gene involved in cell signaling. They thought the gene had something to do with muscle development, and sure enough, they found that these mice had some pretty definite abnormalities in their muscles. For example, when an exercise wheel was put in their cages, the mice ran and ran. The wheels were rigged to devices that counted the number of spins they took, and the researchers converted that number to a distance. They found that during just one night (the active period for mice), mutant mice ran an average of 5.4 kilometers on their wheels.

(5K is a much longer haul for a mouse than a human. How much longer? A very rudimentary calculation* tells me that the distance run by the mutant mice each night is roughly proportional to 65 miles for a human. That's not to say that the effort expended would be proportional--I'm no expert on the mechanics of mouse locomotion, and having four legs probably changes things. But that's about how far the same number of strides would take us.)

Even when they weren't on their exercise wheels, the mutant mice were more active, constantly scurrying around their cages. To find out what let the mice stay so active, the researchers took muscles** out of their legs and examined them. Muscles are often described as fast-twitch, used for quick bursts of activity, or slow-twitch, better suited for aerobic exercise. When the researches contracted the cut-out muscles electrically, muscles that should have been fast-twitch fatigued more slowly than usual. Under a microscope, those same muscles contained more muscle fibers and more mitochondria (the cellular powerhouses). Overall, the fast-twitch muscles now looked like slow-twitch ones.

The mutant mice were also skinnier than normal mice, which isn't much of a surprise.

One wonders if these mice, now overly suited for marathoning, were worse at fast-twitch activities such as sprinting or bench-pressing. Sadly, the authors didn't set up any mouse decathlons to find out. But they did look for related genetic variations in humans.

You can't remove a gene from a person like you can from a mouse (at least, ethics boards would probably frown upon it), but you can look for mutations that already exist in human DNA. Conveniently, the gene that was studied in the marathoner mice exists in a few different variants in humans. The researchers looked at DNA from 209 elite athletes in 11 different sports. When broken down by sport, some of the groups displayed distinct genetic profiles. Cyclists, for example, were more likely than usual to have a certain variant of the gene--while triathletes and elite rowers were more likely to have another variant.

In humans, as in mice, the gene in question seems to be involved in how muscles develop. The authors speculate that further research on this gene could help people with muscular diseases, or the obese or elderly. Increasing a person's muscular endurance could help them to lose weight or to keep active in old age. (It could also help professional cyclists cheat, as if they needed any help in that area.)

It's still not clear how a mutant muscle type affects a mouse's or human's motivation to move. The mice in the study weren't put on wheels and forced to run until they collapsed; they voluntarily got up and ran a 5K every night because they felt like it. Maybe this, too, will be a key insight into obesity--the condition of your muscles may not be independent from your desire to exercise. Something at a cellular level told the mice to just keep moving. If we could tap into that force in our own bodies, we might all be able get ourselves off the couch and onto the exercise wheel.

*I converted the distance into strides using this site's measurement of mouse stride length (moving at average speed) and this site's reported stride length for a female marathoner. Better calculations, or ideas about how to compare distances between small four-legged animals and tall bipeds, are welcome.


**Linguistic point of interest: "Muscle" comes from the Latin for "little mouse."

Pistilli, E., Bogdanovich, S., Garton, F., Yang, N., Gulbin, J., Conner, J., Anderson, B., Quinn, L., North, K., Ahima, R., & Khurana, T. (2011). Loss of IL-15 receptor α alters the endurance, fatigability, and metabolic characteristics of mouse fast skeletal muscles Journal of Clinical Investigation DOI: 10.1172/JCI44945