Secret of Usain Bolt's speed unveiled

Scientists say they can explain Usain Bolt's extraordinary speed with a mathematical model.
His 100m time of 9.58 seconds during the 2009 World Championships in Berlin is the current world record.
They say their model explains the power and energy he had to expend to overcome drag caused by air resistance, made stronger by his frame of 6ft 5in.
Writing in the European Journal of Physics, the team hope to discover what makes extraordinary athletes so fast.
According to the mathematical model proposed, Bolt's time of 9.58 seconds in Berlin was achieved by reaching a speed of 12.2 metres per second, equivalent to about 27mph.
Less dynamic
The team calculated that Bolt's maximum power occurred when he was less than one second into the race and was only at half his maximum speed. This demonstrates the near immediate effect of drag, which is where air resistance slows moving objects.
They also discovered less than 8% of the energy his muscles produced was used for motion, with the rest absorbed by drag.
When comparing Bolt's body mass, the altitude of the track and the air temperature, they found out that his drag coefficient - which is a measure of the drag per unit area of mass - was actually less aerodynamic than that of the average man.
Effects of drag
Jorge Hernandez of the the National Autonomous University of Mexico said: "Our calculated drag coefficient highlights the outstanding ability of Bolt. He has been able to break several records despite not being as aerodynamic as a human can be.
"The enormous amount of work that Bolt developed in 2009, and the amount that was absorbed by drag, is truly extraordinary.
"It is so hard to break records nowadays, even by hundredths of a second, as the runners must act very powerfully against a tremendous force which increases massively with each bit of additional speed they are able to develop.
"This is all because of the 'physical barrier' imposed by the conditions on Earth. Of course, if Bolt were to run on a planet with a much less dense atmosphere, he could achieve records of fantastic proportions.
"The accurate recording of Bolt's position and speed during the race provided a splendid opportunity for us to study the effects of drag on a sprinter.
"If more data become available in the future, it would be interesting to see what distinguishes one athlete from another," added Mr Hernandez.
Bolt's time in Berlin was the biggest increase in the record since electronic timing was introduced in 1968.
Large stride
John Barrow at Cambridge University who has previously analysed how Bolt could become even faster, explained that his speed came in part due his "extraordinary large stride length", despite having such an initial slow reaction time to the starting gun.
"He has lots of fast twitch muscle fibres that can respond quickly, coupled with his fast stride is what gives him such an extraordinary fast time."
He said Bolt has lots of scope to break his record if he responded faster at the start, ran with a slightly stronger tail-wind and at a higher altitude, where there was less drag.
Bolt's Berlin record was won with a tail wind of only 0.9m per second, which didn't give him "the advantage of helpful wind assistance", he added.
"You're allowed to have a wind no greater than 2m per second to count for record purposes, so without becoming any faster he has huge scope to improve," Prof Barrow told BBC News.

HPV Vaccine Might Shield Women Against Throat Cancer: Study

Vaccination already recommended for boys and girls to guard against sexually transmitted infections

FRIDAY, July 19 (HealthDay News) -- Young women who are vaccinated against the human papillomavirus (HPV) not only protect themselves from cervical cancer, but from throat cancer as well, a new study suggests.

Many of the increasing number of throat cancers, seen mostly in developed countries, are caused by HPV infection and the HPV vaccine might prevent many of these cancers, the researchers say.

"We found the women who had the HPV vaccine had much less infection than the women who hadn't," said lead researcher Dr. Rolando Herrero, at the International Agency for Research on Cancer in Lyon, France.

"In fact, there was a 90 percent reduction in the prevalence of HPV infection in the women who received the vaccine compared to the women who had not," he said.

HPV infection is strongly associated with cancer of the oral cavity, Herrero noted. "We think that it is possible that the prevention of the infection will also lead to the prevention of these cancers," he explained.

The HPV vaccine has enormous benefit, said Herrero, "because of the cervical cancer prevention and the anal cancer prevention, and it can even prevent infections in their sexual partners."

Herrero said boys, too, should be vaccinated to protect them from oral cancers. Oral cancer is much more prevalent among men than in women, he pointed out.

A 2011 study in the Journal of Clinical Oncology showed that in the United States, HPV-positive oral cancers increased from 16 percent of all oral cancers in the 1980s to 70 percent in the early 2000s.

And according to the Oral Cancer Foundation, nearly 42,000 Americans will be diagnosed with oral and throat cancer in 2013, and more than 8,000 people will die from these conditions.

HPV-linked throat cancer recently came to the public's attention when the British newspaper The Guardian reported that actor Michael Douglas' recent bout with the disease might have been caused by oral sex.

For the new study, Herrero's team randomly assigned more than 7,400 women aged 18 to 25 to either receive the HPV vaccine or a vaccine against hepatitis A, as a comparison.

Women in the HPV vaccine group were given Cervarix, one of two vaccines available for HPV prevention. (The other is Gardasil.)

Four years later, the researchers found the HPV vaccine was 93 percent effective in preventing throat cancer. Among women who received the HPV vaccine, only one patient showed an oral HPV infection, compared with 15 in the hepatitis A vaccine group, the researchers found.

The HPV vaccine costs $130 a dose and because three shots are required, the total cost is about $390, according to the U.S. Centers for Disease Control and Prevention. There are government programs that can help offset these costs for some patients, the agency noted.

Because HPV is a sexually transmitted infection, the vaccine is most effective when given before someone is sexually active. Eighty percent of people will test positive for HPV infection within five years of becoming sexually active, said Dr. Marc Siegel, an associate professor of medicine at NYU Langone Medical Center, in New York City.

That's why the CDC recommends the vaccine for adolescent girls and boys starting at age 11.

The new report was published in the July issue of the online journal PLoS One.

"The study is really preliminary information," said Dr. Elizabeth Poynor, a gynecologic oncologist and pelvic surgeon at Lenox Hill Hospital, in New York City. "It will provide a basis to begin to study how the vaccine will help to protect against throat cancer," she noted.

"It's going to take a while to study those who have been vaccinated to determine that they are protected against throat cancer. This is just the beginning," she said.

"It also really highlights that we need to vaccinate young boys," Poynor added.

Overweight? Maybe You Really Can Blame Your Genes

The mice were eating their usual chow and exercising normally, but they were getting fat anyway. The reason: researchers had deleted a gene that acts in the brain and controls how quickly calories are burned. Even though they were consuming exactly the same number of calories as lean mice, they were gaining weight.

So far, only one person — a severely obese child — has been found to have a disabling mutation in the same gene. But the discovery of the same effect in mice and in the child — a finding published Wednesday in the journal Science — may help explain why some people put on weight easily while others eat all they want and seem never to gain an ounce. It may also offer clues to a puzzle in the field of obesity: Why do studies find that people gain different amounts of weight while overeating by the same amount?

Scientists have long thought explanations for why some people get fat might lie in their genes. They knew body weight was strongly inherited. Years ago, for example, they found that twins reared apart tended to have similar weights and adoptees tended to have weights like their biological parents, not the ones who reared them. As researchers developed tools to look for the actual genes, they found evidence that many — maybe even hundreds — of genes may be involved, stoking appetites, making people voraciously hungry.

This rare gene-disabling mutation, though, is intriguing because it seems to explain something different, a propensity to pile on pounds even while eating what should be a normal amount of food. Investigators are now searching for other mutations of the same gene in fat people that may have a similar, but less extreme effect. The hope is that in the long term, understanding how this gene affects weight gain might lead to treatments for obesity that alter the rate at which calories are burned.

“The history of obesity for many many years has been one of blaming people for lack of self control,” said Dr. Joseph Majzoub, chief of endocrinology at Boston Children’s Hospital and lead author of the new paper. “If some of it is due to a slow metabolism, that would completely change the perspectives of parents and patients. It really would change the way we think of the disease.”

In their paper, Dr. Majzoub and his colleagues describe figuring out how the gene they deleted, known as MRAP2, acts in the brain to control weight. They discovered that it is a helper gene. It normally acts in the brain to signal another gene already known to be involved in controlling appetite. So they developed a hypothesis. If the helper gene was deleted, the brakes should come off the gene that controls appetite. Animals should eat voraciously.

The first thing they noticed was that the mice got fat, ending up weighing twice as much as their normal siblings, with most of that extra weight due to fat accumulation.

“During the mouse equivalent of childhood and adolescence they were becoming rapidly obese,” Dr. Majzoub said.

The surprise came when the researchers figured out why. When the mice were young, they had normal appetites. The researchers measured what they and their normal siblings ate and determined they were eating the same amount of food. Yet the mice with the deleted gene still gained weight. The only way the obesity-prone mice could be kept slim was to be fed 10 to 15 percent less than their siblings.

But as adults, the mice with the missing gene developed monstrous appetites. Given a chance, they ate much more than their siblings, exacerbating the effects of their tendency to turn food into fat.

That led the researchers to ask if the same genetic phenomenon could be making people obese. They contacted Dr. Sadaf Farooqui of the University of Cambridge, whose group has been mapping the genes of massively obese children, and studied the data on 500 of the children, searching for mutations that disabled the same gene they had deleted in mice.

One child clearly had a gene-disabling mutation and three others had mutations that the investigators suspect might render the gene nonfunctional. None of the normal-weight children who served as controls had a mutation in the helper gene.

“From a basic science point of view, this is really interesting and exciting,” said David Allison, an obesity researcher at the University of Alabama in Birmingham who was not involved in the study. Any discovery that helps fill in the details of how the brain controls eating and weight gain is important, he added.

Jeffrey Friedman, an obesity researcher at Rockefeller University, who also was not involved in the study, said, “It is another piece in a very important puzzle.”

The work fascinates Claude Bouchard, a genetics researcher at the Pennington Biomedical Research Center in Baton Rouge, La., because it might offer insight into an intriguing finding: there are genetic controls not just of how much people want to eat but also how much of what they eat turns into fat or is burned off and not used by the body. Although the common mantra is that a calorie is a calorie and 3,500 extra calories eaten equals a pound of fat on the body, that is not what happens in real life, he found.

For example, in one of his studies, Dr. Bouchard enlisted 12 pairs of lean identical twins to live in an enclosed area for 120 days so their food and exercise could be monitored while they ate 1,000 calories a day more than needed to maintain their weight. The twins in each pair gained about the same amount of weight, but the amount gained varied threefold among the pairs. Those who gained the most put on as much as 29 pounds while those who gained the least put on 9 ½ pounds.

“It is not a freak finding,” Dr. Bouchard said, adding that about 20 studies found the same threefold range in weight gain in response to excess calories. But it also is not clear why this occurs. The intriguing possibility, he said, is that the newly discovered gene might be among those involved. The level of its activity might help determine how quickly calories are burned.

Dr. Majzoub and his colleagues are now trying to determine whether additional mutations in the gene they discovered — ones that hinder its function but do not completely disable it — might explain why some people gain weight.

“All we can do is hope,” Dr. Majzoub said.

1

Man Officially Cured of HIV

For the first time, a man has been declared officially cured of HIV. The remedy may nearly have killed him, but it opens a door—just a crack—to hope that we may someday kill off the scourge for good.

Strangely enough, the diagnosis that most concerned Timothy Ray Brown in 2007 was acute myeloid leukemia. HIV has been increasingly thought of as a manageable disease, though certainly a terribly burdensome one. What brought the 42-year old Brown under the care of Germany's Charite Universitatsmedizin Berlin hospital was the more immediate threat his cancer posed.

The treatment Brown underwent was aggressive: chemotherapy that destroyed the majority of his immune cells. Total body irradiation. Finally, a risky stem-cell transplant that nearly a third of patients don't survive—but that appears to have completely cured Brown of HIV.

Doctors were savvy when they chose a stem cell donor for Brown. The man whose bone marrow they used has a particular genetic mutation, present in an incredibly small percentage of people, that makes him almost invulnerable to HIV. With Brown's own defenses decimated by treatments, the healthy, HIV-resistant donor cells repopulated his immune system. The initial indications that the virus had abated were promising. But only just now, having taken no antiretroviral drugs since the transplant, and following extensive testing shows no signs whatsoever of HIV, have his doctors given the official word:

He's cured.

What does this mean for the future of treatment? It's not as though every HIV patient can or would want to go through the tremendous suffering that was prelude to Brown's recovery, or be able to afford the procedure if they could or did. But for the first time, we know that HIV can be cured, not just managed. It opens new avenues of research—gene therapy, stem cell treatments—that may otherwise have been thought dead ends. [AIDS Map]

High-carb meals pique cravings for more, study says

By Melissa Healy
12:00 PM PDT, June 27, 2013

advertisement

Tucking into a breakfast of buttermilk pancakes and maple syrup, or a great bowl of white pasta for lunch, not only sends your blood sugar soaring--and then, suddenly, plummeting. Four hours after you've put down your fork, such a meal makes you hungrier than if you'd eaten one with more protein and fiber and fewer carbohydrates, a new study finds.
The study also demonstrates that four hours later, the echo of that meal activates regions of the brain associated with craving and reward seeking more powerfully than does a meal with a lower "glycemic load."
The result: At your next opportunity to eat, you'll not only be hungrier; you'll be looking for more of the same.
The study, conducted by researchers from Harvard Medical School and Boston Children's Hospital, was published this week in the American Journal of Clinical Nutrition. The team was led by Dr. David S. Ludwig, director of Boston Children's Hospital Obesity Prevention Center and author of Ending the Food Fight: Guide Your Child to a Healthy Weight in a Fast Food/Fake Food World.
And what's the result of repeating this cycle meal after meal? The Harvard researchers surmise that the striatum, a key node in the brain's reward circuitry, may lose its sensitivity to the neurotransmitter dopamine, increasing a person's drive to eat high-carb foods and disrupting his or her ability to control that impulse.
The team saw many of those processes at work in a lab where on two separate occasions, 12 overweight or obese young men were offered one of two meals: one high in glycemic load (including refined sugars or carbohydrates) and the other, a meal with a low-glycemic load. The meals were equal in calories, as well in their relative protein, carbohydrate and fat content, and were rated equally tasty by subjects. But while the high-glycemic load meal contained such ingredients as corn syrup and Lactaid milk, the low-glycemic load meal contained corn syrup and regular low-fat milk.
Over the next several hours, the men not only had their blood drawn to gauge their metabolic response to the meals; they also assessed their perceived degree of hunger, and underwent a scan focusing on several nodes of their brain's reward circuitry in a functional Magnetic Resonance Imager.
While the two meals elicited very similar reactions from subjects--they found both meals appealing--their brains and blood revealed dramatically contrasting responses. Four hours later, those who'd consumed the high-glycemic meal had lower blood glucose levels and said they felt hungrier than those who'd had the low-glycemic meal. Activity in the right nucleus accumbens and related reward circuitry, as well as in the region of the cortex that processes smell and taste, was significantly higher in those who'd consumed the high glycemic load meal than in subjects who'd consumed the low glycemic-load meal.
The combination of plummeting blood sugar levels, a greater sensation of hunger, and a memory of a meal high on the glycemic index led to the researchers' conclusion: "This combination of physiological events may foster food cravings with a special preference for high [glycemic load] carbohydrates, thereby propagating cycles of overeating." 
Want to understand the difference between high-glycemic load foods and those lower in glycemic load? Here's a good explanation. And here's a helpful list.

Worried about type 2 diabetes? Walk after every meal

A new study shows the benefits of walking for 15 minutes after every meal.

(Photo: Bob Riha Jr., USA TODAY)

STORY HIGHLIGHTS

• Walking after every meal is as beneficial for blood sugar as a 45-minute walk
• Taking a 15-minute walk after dinner helps control post-meal blood sugar
• The timing of exercise is important, study shows

If you're at risk for developing type 2 diabetes, then take a 15-minute walk after every meal.

A study, out today, shows that moderately-paced walks after meals work as well at regulating overall blood sugar in adults with pre-diabetes as a 45-minute walk once a day.

And there's an added benefit of walking after every meal, especially dinner: It helps lower post-meal blood sugar for three hours or more, the research found.

Walking after a meal "really blunts the rise in blood sugar," says the study's lead author Loretta DiPietro, professor and chair of the department of exercise science at the George Washington University School of Public Health and Health Services.

"You eat a meal. You wait a half-hour and then you go for a 15-minute walk, and it has proven effective in controlling blood sugar levels, but you have to do it every day after every meal. This amount of walking is not a prescription for weight loss or cardiovascular fitness — it's a prescription for controlling blood sugar," she says.

The Italians call the walk after dinner a passeggiata and know it aids in digestion, DiPietro says. "Now we know it also helps the clearance of blood sugar."

Currently, almost 26 million children and adults (8.3% of the population) in the USA have diabetes, and about 79 million Americans have pre-diabetes. In diabetes, the body does not make enough of the hormone insulin, or it doesn't use it properly. Insulin helps glucose (sugar) get into cells, where it is used for energy. If there's an insulin problem, sugar builds up in the blood, damaging nerves and blood vessels.

DiPietro and colleagues worked with 10 overweight, sedentary volunteers, who were an average age of 71. All had higher than normal blood sugar levels and were considered pre-diabetic, which means they were at risk for developing type 2 diabetes, the most common type.

Each participant stayed in a metabolic chamber, a special room that helps researchers track the calories burned by the volunteers, for two days on three separate occasions.The first day on each occasion was considered a control day, and participants did no physical activity.

On the second day, the participants did one of three things: They walked at an easy to moderate pace (about 3 mph) on a treadmill for 15 minutes — about a half hour after each meal.

On the other days the participants either walked for 45 minutes at 10:30 a.m. or they walked the same amount of time at 4:30 p.m. Their blood sugar levels were measured continuously throughout the two-day period.

The research, published in the June issue of Diabetes Care, shows that the timing of walks is important for providing health benefits, DiPietro says. Walking is beneficial because the muscle contractions "help to clear blood sugar," she says.

After dinner is a good time to get up and walk with your partner, a neighbor or your dog, she says. If you can't go outside, then march in place for 15 minutes, she says.

After lunch, many employees go and sit down for another four hours, but based on these findings, companies and businesses should make it easier for employees to go out and take a walk after lunch, says Tim Church, director of preventive medicine research at the Pennington Biomedical Research Center in Baton Rouge.

John Anderson, president of medicine and science for the American Diabetes Association, says it makes sense that a short walk would lower post-meal blood sugar. "What we don't know is if it is going to make a big difference over time in people's progression from prediabetes to diabetes — any more than the standard exercise advice of walking 30 minutes a day five days a week."

Other research shows that amount of exercise and a weight loss of 5% to 7% helps reduce the risk of developing the disease, Anderson says.

DiPietro says the results of this study may also apply to pregnant women who are at risk for gestational diabetes, and the findings may also be helpful to people who aren't able to walk for 45 minutes at a time but are able to do 15 minutes.

The study was sponsored by the National Institute on Aging, part of the National Institutes of Health.

The government's exercise guidelines recommend that:

• Adults get at least 2½ hours of moderate-intensity physical activity each week, such as brisk walking, or 1¼ hours of a vigorous-intensity activity, such as jogging or swimming laps, or a combination of the two types, to get the most health benefits from exercise. These aerobic activities should be done in at least 10-minute bouts.

• To get even more health benefits, people should do five hours of moderate-intensity physical activity each week or 2½ hours of vigorous activity.

• Adults should do muscle-strengthening (resistance) activities at a moderate- or high-intensity level for all major muscle groups two or more days a week. This should include exercises for the chest, back, shoulders, upper legs, hips, abdomen and lower legs. The exercises can be done with free weights or machines, resistance bands, calisthenics that use body weight for resistance (push-ups, pull-ups, sit-ups), or carrying heavy loads or doing heavy gardening such as digging or hoeing.

Short walks 'could cut diabetes risk in older people'

A 15-minute walk after each meal could prevent older people developing type-2 diabetes, a study has found.

The post-meal walks control blood sugar as well as one long walk, research by George Washington University suggested.

Elevated blood sugar after meals could increase the risk of type-2 diabetes, so resting after eating "is the worst thing you can do", the study said.

Diabetes UK said there were "small differences" between exercise routines - but any activity was beneficial.

The US study was the first to test short bouts of exercise in the "risky period" following meals, when blood sugar can rise rapidly, lead author Loretta DiPietro said.

'Blunting effect'

She said high blood sugar after meals was a key risk factor in the progression from impaired glucose tolerance - what the study called "pre-diabetes" - to type-2 diabetes and cardiovascular disease.

The study found three 15-minute walks were as effective at reducing blood sugar over a 24-hour period as one 45-minute walk of the same "easy-to-moderate" pace.

But walking after food was "significantly more effective" at "blunting the potentially damaging elevations in post-meal blood sugar commonly observed in older people".

Older people may be "particularly susceptible" to poor blood sugar control after meals due to insulin resistance in the muscles and slow or low insulin secretion from the pancreas, the researchers said.

They found the best time to walk was after the evening meal, which is often the largest of the day and therefore causes the greatest rise in blood sugar.

More research needed

This increase often lasted "well into the night and early morning", the study found, but it was "curbed significantly" as soon as people started to walk.

Researchers studied 10 people aged 60 and over who were at risk of developing type-2 diabetes due to higher-than-normal levels of fasting blood sugar and insufficient physical activity.

Dr DiPietro said the findings could lead to an "inexpensive strategy" for preventing type-2 diabetes, but said the results must be confirmed by larger trials.

Weight loss and exercise are widely accepted as key ways to prevent type-2 diabetes, which occurs when the body does not produce enough insulin to function properly, or the body's cells do not react to insulin.

Diabetes UK estimates there are up to seven million UK people at "high risk" of developing type-2 diabetes.

Dr Matthew Hobbs, the charity's head of research, said the study reinforced the message that exercise was "extremely important" to reduce the risk.

Talking about the comparison between one 45-minute walk and three 15-minute walks after meals, he added: "Although there were some small differences, the important take-home message is that doing any physical activity, even at a low intensity, is good for you."