Isegoria

Are humans born to run long distances or short sprints?

One of the most intriguing genes discovered, ACTN3 encodes a protein that governs metabolism in “fast twitch” muscle fibres, which generate force at high speed.

Around 18 percent of the world’s population has a truncated variant of the gene which blocks this protein. The stubby variant, called R577X, is common among successful endurance athletes, previous research has found.

On the other hand, elite sprinters, who need explosive speed, are likelier to have the reverse — a functioning variant of ACTN3.
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The apparent reason for this: the loss of ACNT3′s protein was compensated by a different protein, called alpha-actinin-2, which shifted muscle metabolism towards a smoother, more efficient, aerobic pathway.
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North’s team also looked through genetic profiles from individuals of European and East Asian descent and found that there was remarkably little sign of mutation in the wider stretch of genetic code in the vicinity of R577X.

Such similarity is a telltale sign of what evolutionary experts call positive selection. Genes which help the fight for survival get lastingly incorporated in the human genome, whereas those that encumber it get weeded out.
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According to North’s calculations, R577X took root among populations in central Europe around 15,000 years ago and in East Asia around 33,000 years ago.

Tour de France cyclists have big hearts — literally:

Researchers who examined the hearts of former Tour bikers found that the athletes’ hearts were from 20 to 40 percent larger than average, said Dr. Francois Carre of the Centre Hospitalier Universitaire de Rennes, France, speaking at a meeting of the European Society of Cardiology.
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Carre found that the athletes’ hearts shrank nearly a quarter in size after they finished riding professionally. Still, the cyclists remained in excellent physical condition.

This still leaves some questions: How big were the cyclists hearts before they started training? Did they start with larger hearts, or did they possess hearts that adapted more to training than others’? Or did their hearts grow as a result of performance-enhancing drugs?

Body Mass Index, or BMI, may be a flawed measure of health and fitness, but if you look at the interactive map from The Obesity Fight, you immediately realize that all those people aren’t creeping over 30 kg/m² by lifting weights and putting on muscle.

Mark Sisson notes that Training is no guarantee of health:

The problem with many, if not most, age group endurance athletes is that the low-level training gets out of hand. They overtrain in their exuberance to excel at racing, and they over consume carbohydrates in an effort to stay fueled. The result is that over the years, their muscle mass, immune function, and testosterone decrease, while their cortisol, insulin and oxidative output increase (unless you work so hard that you actually exhaust the adrenals, introducing an even more disconcerting scenario). Any anti-aging doc will tell you that if you do this long enough, you will hasten, rather than retard, the aging process. Studies have shown an increase in mortality when weekly caloric expenditure exceeds 4,000.

That’s why I stopped racing and training ten years ago and why I prefer hiking, sprinting and weight-training today. But what’s a competitive type-A to do if s/he wants to kick age-group butt in Kona and NOT fade away prematurely?

Given carte blanche to take advantage of all that medicine has to offer, I would aggressively consume antioxidants during my training (10-20,000 ORAC units per day), I would increase the amount of healthy fats (omega 3-rich) in my diet to 50% of total calories and I would only consume quality complex carbohydrates during my training. In fact, I would calculate my carbohydrate requirements on a daily basis and not exceed them. I would use simple sugars (e.g., gels) during long rides and races only to the extent they are necessary. That means I would do most of my training without them, saving them for races. I would work closely with a trained anti-aging doctor to monitor my fasting glucose, fasting insulin, free and bound testosterone, liver enzymes, cortisol, DHEA, hematocrit, ferritin and other parameters.

Read the whole article.

We shouldn’t be surprised that Obesity is ‘socially contagious’:

The [NEJM] study — the first to examine this phenomenon — finds that if one person becomes obese, those closely connected to them have a greater chance of becoming obese themselves. Surprisingly, the greatest effect is seen not among people sharing the same genes or the same household but among friends.

An odd stat:

If a person you consider a friend becomes obese, the researchers found, your own chances of becoming obese go up 57 percent. Among mutual friends, the effect is even stronger, with chances increasing 171 percent.

Aren’t most friends mutual friends?

More:

Christakis and Fowler also looked at the influence of siblings, spouses and neighbors. Among siblings, if one becomes obese, the likelihood for the other to become obese increases 40 percent; among spouses, 37 percent. There was no effect among neighbors, unless they were also friends.

The researchers analyzed data over a period of 32 years for 12,067 adults, who underwent repeated medical assessments as part of the Framingham Heart Study. They were able to map a densely interconnected social network of the study’s subjects by using the tracking sheets (which had previously been archived in a basement) that recorded not only the subjects’ family members but also unrelated friends who could be expected to find them in a few years.

The network map took two years to assemble and includes information on the participants’ body-mass index. Among the first things the researchers noticed was that, consistent with other studies finding an obesity epidemic in the U.S., the whole network grew heavier over time.

Also immediately apparent were distinct clusters of thin and heavy individuals. Statistical analysis revealed that this clustering could not be attributed solely to the selective formation of ties among people of comparable weights.

“It’s not that obese or non-obese people simply find other similar people to hang out with,” said Christakis, a physician and a professor in Harvard Medical School’s department of health care policy. “Rather, there is a direct, causal relationship.”

Further analysis also suggested that people’s influence on each other’s obesity status could not be put down just to similarities in lifestyle and environment, to, for example, people eating the same foods together or engaging in the same physical activities. Not only do siblings and spouses have less influence than friends, but also geography doesn’t play a role. The striking impact of friends seems to be independent of whether or not the friends live in the same region.

“When we looked at the effect of distance, we found that your friend who’s 500 miles away has just as much impact on your obesity as [one] next door,” said Fowler, an associate professor of political science at UC San Diego and an expert in social networks.

In part because the study also identifies a larger effect among people of the same sex, the researchers believe that people affect not only each other’s behaviors but also, more subtly, norms.

“What appears to be happening is that a person becoming obese most likely causes a change of norms about what counts as an appropriate body size. People come to think that it is okay to be bigger since those around them are bigger, and this sensibility spreads,” said Christakis.

The truth about why we walk on two legs: it saves energy:

Scientists compared the amount of energy expended by humans and chimps when walking on a treadmill and found that a two-legged gait is about 75 per cent less costly compared with walking on all fours.

The results provide powerful evidence in support of the idea that the bipedal gait of humans became established because it was more energy efficient and so required less food.

Rival Theories:

• Tree walking: A recent theory suggests that our tree-living ancestors walked upright on branches, using their arms for balance. The idea is based on observing modern-day orang-utans, which often move around in trees by walking on two legs, gripping the branches with their hands.
• A cooling effect: Another idea is that it was cooler to walk upright in savannah grasslands because by doing so there was less surface area of the body exposed to the Sun.
• Wading in water: If our ancestors had to wade through water, they would have learned to walk on two legs. Modern-day chimps often adopt a two-legged gait when walking through water.