Isegoria

Al Fin shares an amusing cartoon. I hope I don’t ruin the joke by pointing out that the average age of paleolithic humans might have been quite low, but some early humans lived to be quite old.

Years ago, when I was taking a fairly long course of hardcore antibiotics for a sinus infection, I noticed that my Achilles tendons would pop where they attached to the bone. I wasn’t sure what to make of it until I stumbled across a study noting that tendon injuries were higher in athletes who had recently taken antibiotics. When I mentioned this to my doctor, he looked at me like I was delusional.

Now the Food and Drug Administration has ordered makers of fluoroquinolone drugs — like Cipro, Levaquin, and Floxin — to add a “black box” warning that they can cause tendon ruptures.

If we look at humans as climbers, we’re not half-bad:

A fascinating brief study published in Science (May 16 2008) shows the cost of climbing a meter per unit of body mass is essentially the same over non-human primates and humans (Hs in the figure). The data are all matched for climbing speed. Walking efficiency is also indicated in yellow.

We homo sapiens are pretty efficient climbers, though being the largest of the primates we may be a bit slower at it. On the other hand we are more efficient in walking. The reason for that is we have longer legs per unit of body mass.

This Time, He'll Be Left Breathless looks at “endurance artist” David Blaine and modern free divers:

A century ago, Houdini was celebrated for being able to hold his breath for three and a half minutes. Today even a novice can quickly learn to last longer than that, as I discovered under the tutelage of Kirk Krack, the free-diving coach who has been training Mr. Blaine for his world-record attempt.
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Researchers in the 1960s calculated, based on lung capacity and the effect of water pressure, that humans couldn’t dive deeper than 165 feet. Today free divers are going down more than 600 feet and returning in apparently fine shape. Most of the time.

The day before his attempt in the pool, Mr. Blaine was practicing in the ocean and told me he was headed down for a dive of 100 feet, so routine that he didn’t bother doing the usual preparatory ritual: a slow, steady “breathe-up,” followed by exhalations to purge carbon dioxide and then a final series of quick gulps of air called lung-packing.

I watched him disappear into the depths and then reappear about two minutes later, swimming smoothly upward next to a guide rope. But about 20 feet from the surface, he suddenly veered away from the rope and appeared to struggle upward with his arms flailing. His coach, Mr. Krack, recognized the symptoms of a blackout instantly and rushed to grab Mr. Blaine, supporting his head above the surface until he regained consciousness.

He’d succumbed, Dr. Potkin said, to one of the most common and sometimes fatal dangers of free diving — and one of the reasons you shouldn’t try any prolonged breath-holding unless someone like Mr. Krack is supervising.

“Divers rarely get into trouble at depth,” Dr. Potkin said. “But as the diver approaches the surface, the decreasing water pressure causes a drop in pressure of the oxygen in the brain. If the level in the brain gets too low, it’s like a switch: lights out.”

More:

The natural impulse to stop holding your breath (typically within 30 seconds or a minute) is not because of an oxygen shortage but because of the painful buildup of carbon dioxide. Mr. Blaine said he began trying to overcome that urge when he was a child in Brooklyn and at age 11 managed to hold his breath for three and a half minutes.

In his current training, he said, he does exercises every morning in which he breathes for no more than 12 minutes over the course of an hour, and he sleeps in a hypoxic tent in his Manhattan apartment that simulates the thin air at 15,000 feet above sea level.

He has been concentrating on lowering his oxygen consumption by slowing his metabolism, partly through diet (he fasted for 18 hours before the breath-hold in the pool) and partly through relaxation. In a test by Dr. Potkin, Mr. Blaine on command quickly lowered his heart rate by 25 percent.

“David seems to have a phenomenal ability, like Buddhist monks, to control his body,” Dr. Potkin said.

When Mr. Blaine began his breath-hold in the pool, his heart rate during the first minute fell to 46 from 81, a drop that was not entirely his own doing. Immersing the face in water produces a protective action in humans similar to that in dolphins, seals, otters and whales. Called the mammalian diving reflex, it quickly lowers the heart rate and then constricts blood vessels in the limbs so that blood is reserved for the heart and the brain.

By exploiting that reflex, free divers can remain active underwater for more than four minutes, and much longer if they remain still. The world-record holders have exceeded nine minutes after filling their lungs with ordinary air, and more than 16 minutes after inhaling pure oxygen.

According to Adam Sternbergh, You Walk Wrong — because you’re wearing shoes:

Last year, researchers at the University of the Witwatersrand in Johannesburg, South Africa, published a study titled “Shod Versus Unshod: The Emergence of Forefoot Pathology in Modern Humans?” in the podiatry journal The Foot. The study examined 180 modern humans from three different population groups (Sotho, Zulu, and European), comparing their feet to one another’s, as well as to the feet of 2,000-year-old skeletons. The researchers concluded that, prior to the invention of shoes, people had healthier feet. Among the modern subjects, the Zulu population, which often goes barefoot, had the healthiest feet while the Europeans — i.e., the habitual shoe-wearers — had the unhealthiest. One of the lead researchers, Dr. Bernhard Zipfel, when commenting on his findings, lamented that the American Podiatric Medical Association does not “actively encourage outdoor barefoot walking for healthy individuals. This flies in the face of the increasing scientific evidence, including our study, that most of the commercially available footwear is not good for the feet.”

Shoe designers are starting to design minimalist shoes with extremely thin, flexible soles:

At first glance, this seems like a sensible and obvious approach — to work with the foot, not against it. But it represents a fundamental break from the dominant philosophy of shoe design. For decades, the guiding principle of shoe design has been to compensate for the perceived deficiencies of the human foot. Since it hurts to strike your heel on the ground, nearly all shoes provide a structure to lift the heel. And because walking on hard surfaces can be painful, we wrap our feet in padding. Many people suffer from flat feet or fallen arches, so we wear shoes with built-in arch supports, to help hold our arches up.

There are, of course, a thousand other factors that have influenced shoe design through the ages; for example, people like shoes that look nice. High heels have never, ever been comfortable, but they do make the wearer feel sexy. In fact, the idea of strolling idly through urban environments has only been fashionable, or even feasible, in Western society for about 200 years. Before that, cities had few real sidewalks, the streets were swimming in sewage, and walking as a form of locomotion was associated with poverty and the working class. “Only the upper classes, and especially women, could wear shoes that clearly defined an inability to walk very far,” writes Peter McNeil and Giorgio Riello in the essay “Walking the Streets of London and Paris: Shoes in the Enlightenment.” Walking was for peasants, who were “barefoot and pregnant”; the rich, or “well-heeled,” took carriages.

Of course, more recently we’ve become interested in shoes that are promoted as being comfortable, whether they’re cushioned walking shoes or high-tech sneakers with pumps and torsion bars. Still, the basic philosophy — that shoes have to augment, or in some cases supersede, or in some cases flat-out ignore, the way your foot works naturally — has remained the same. We were not born with air bubbles in our soles, so Nike provided them for us.

Try this test: Take off your shoe, and put it on a tabletop. Chances are the toe tip on your shoes will bend slightly upward, so that it doesn’t touch the table’s surface. This is known as “toe spring,” and it’s a design feature built into nearly every shoe. Of course, your bare toes don’t curl upward; in fact, they’re built to grip the earth and help you balance. The purpose of toe spring, then, is to create a subtle rocker effect that allows your foot to roll into the next step. This is necessary because the shoe, by its nature, won’t allow your foot to work in the way it wants to. Normally your foot would roll very flexibly through each step, from the heel through the outside of your foot, then through the arch, before your toes give you a powerful propulsive push forward into the next step. But shoes aren’t designed to be very flexible. Sure, you can take a typical shoe in your hands and bend it in the middle, but that bend doesn’t fall where your foot wants to bend; in fact, if you bent your foot in that same place, your foot would snap in half. So to compensate for this lack of flexibility, shoes are built with toe springs to help rock you forward. You only need this help, of course, because you’re wearing shoes.

Here’s another example: If you wear high heels for a long time, your tendons shorten—and then it’s only comfortable for you to wear high heels. One saleswoman I spoke to at a running-shoe store described how, each summer, the store is flooded with young women complaining of a painful tingling in the soles of their feet — what she calls “flip-flop-itis,” which is the result of women’s suddenly switching from heeled winter boots to summer flip-flops. This is the shoe paradox: We’ve come to believe that shoes, not bare feet, are natural and comfortable, when in fact wearing shoes simply creates the need for wearing shoes.

Okay, but what about a good pair of athletic shoes? After all, they swaddle your foot in padding to protect you from the unforgiving concrete. But that padding? That’s no good for you either. Consider a paper titled “Athletic Footwear: Unsafe Due to Perceptual Illusions,” published in a 1991 issue of Medicine and Science in Sports and Exercise. “Wearers of expensive running shoes that are promoted as having additional features that protect (e.g., more cushioning, ‘pronation correction’) are injured significantly more frequently than runners wearing inexpensive shoes (costing less than $40).” According to another study, people in expensive cushioned running shoes were twice as likely to suffer an injury — 31.9 injuries per 1,000 kilometers, as compared with 14.3 — than were people who went running in hard-soled shoes.

Reed Albergotti, of the Wall Street Journal, is stunned — stunned! — to find out that the benefits of steroids last long after athletes quit taking them. Cheaters Do Prosper:

In the study, which was completed in October 2006 by the Department of Integrative Medical Biology at Sweden’s Umea University, researchers took muscle biopsies from 26 elite powerlifters who have competed at the sport’s highest levels. Ten of the volunteers said they were not steroid users, but the other 16 had either admitted using these drugs in the past or said they were currently using them. Not only is it unusual for scientists to study elite athletes of any kind, it’s almost impossible to study top athletes who are using steroids in competition.

When the researchers looked at the subjects’ muscles through a microscope, they made a surprising discovery: Rather than returning to their original proportions, the muscles of the steroid users who’d stopped taking the drug looked remarkably similar to those of the subjects who were still using. They also had larger muscle fibers and more growth-inducing “myonuclei” in their muscle cells than the nonsteroid users.

This is not news at all to strength athletes:

The idea that steroids may have lasting benefits comes as no surprise to Larry Maile, president of USA Powerlifting. He says former steroid-using competitors who rehabilitate themselves often become top performers. “They’re still bigger and stronger than they ever would have been,” he says. There is no way to prove that they’re still benefiting from their years of steroid use, he adds, but the question remains, “would they really have been that good had they never used?”

Charles Yesalis, a former strength coach and professor emeritus of health policy and administration at Pennsylvania State University, says athletes who continue to train can retain as much as 85% of their gains from using drugs. This isn’t based on muscle biopsies or peer-reviewed research, he says, but on 30 years of experience with athletes. He says he has talked privately with hundreds of dopers, some of them champions, and has seen the permanent benefits of performance-enhancing drugs. “These things are like rocket fuel,” he says.

I’ve long found the Paleo Diet plausible, but I can’t quite agree with its premise:

The primary tenet of evolutionary medicine is that the profound changes in the environment (e.g., in diet and other lifestyle conditions), which began with the introduction of agriculture and animal husbandry approximately 10,000 years ago, occurred too recently on an evolutionary timescale for natural selection to adjust the human genome.

Evolution doesn’t occur on a geological time scale because it’s a glacially slow (and steady) process, but because there’s rarely a need and opportunity to change in a big way.

If an omnivorous species finds that it can’t hunt prey animals and gather varied plant foods anymore, but it can eat grains, that is a huge new selection pressure. A few hundred generations is plenty of time to evolve a response to that. After all, one generation will cull the herd quite a bit, and it only takes a few generations to artificially select a new breed of dog or cow.

The issue with humans, as I see it, is that the most successful humans, for thousands of years, were those who held onto the hunter-gatherer diet and some of the hunter-gatherer lifestyle by becoming aristocrats — don’t poach the king’s deer! — and lording over the poor peasants, who had to subsist on a monotonous diet while performing monotonous labor.

Evolutionarily, it’s good to be the Khan, and that means that only some humans faced strong pressure to adapt to agriculture, while others retained the old ways and did not face that strong pressure to adapt to agriculture — they faced strong pressure to succeed at war. Then their downwardly mobile descendents ended up as farmers and tradesmen, where aristocratic traits weren’t so adaptive.

Growth hormones don't boost performance — according to scientists, who won’t study athletes using the drugs the way they really use them:

They analyzed 27 studies involving 440 participants. The results were released Monday by the Annals of Internal Medicine.

Researchers found that those who got the hormone put on about 5 pounds more of muscle, and lost about 2 pounds more of fat, although the fat loss wasn’t statistically different. The researchers said some of the extra body mass could just be fluid buildup.

There was no difference found in strength or exercise stamina between the two groups, but there were only two strength studies and eight that measured exercise. Those who got the hormone had more side effects including swelling and fatigue.

The review couldn’t consider long-term effects, since the longest study was three months, and most were much shorter.

The researchers also said the doses used in the research may be lower than those used by athletes, who may be combining growth hormone with other performance-enhancing drugs.

Scientists similarly found that anabolic steroids had no effect on muscle-building — because they refused to look at large doses combined with weight training. When they did finally look at the low end of what bodybuilders were using — 600 mg of testosterone enanthate weekly for 10 weeks — they saw tremendous gains from steroids. Hmm…