Saturday, 13 February 2010

Barefoot Running - avoids heel strike.

  "All you need to run is a pair of shoes."
Not so!

Scientists have found that those who run barefoot, or in minimal footwear, tend to avoid "heel-striking," and instead land on the ball of the foot or the middle of the foot. In so doing, these runners use the architecture of the foot and leg and some clever Newtonian physics to avoid hurtful and potentially damaging impacts, equivalent to two to three times body weight, that shod heel-strikers repeatedly experience.
"People who don't wear shoes when they run have an astonishingly different strike," says Daniel E. Lieberman, professor of human evolutionary biology at Harvard University and co-author of a paper appearing this week in the journal Nature.

"By landing on the middle or front of the foot, barefoot runners have almost no impact collision, much less than most shod runners generate when they heel-strike. Most people today think barefoot running is dangerous and hurts, but actually you can run barefoot on the world's hardest surfaces without the slightest discomfort and pain. All you need is a few calluses to avoid roughing up the skin of the foot. Further, it might be less injurious than the way some people run in shoes."

Working with populations of runners in the United States and Kenya, Lieberman and his colleagues at Harvard, the University of Glasgow, and Moi University looked at the running gaits of three groups: those who had always run barefoot, those who had always worn shoes, and those who had converted to barefoot running from shod running. The researchers found a striking pattern.

Most shod runners -- more than 75 percent of Americans -- heel-strike, experiencing a very large and sudden collision force about 1,000 times per mile run. People who run barefoot, however, tend to land with a springy step towards the middle or front of the foot.
"Heel-striking is painful when barefoot or in minimal shoes because it causes a large collisional force each time a foot lands on the ground," says co-author Madhusudhan Venkadesan, a postdoctoral researcher in applied mathematics and human evolutionary biology at Harvard. "Barefoot runners point their toes more at landing, avoiding this collision by decreasing the effective mass of the foot that comes to a sudden stop when you land, and by having a more compliant, or springy, leg."

The differences between shod and unshod running have evolutionary underpinnings. For example, says Lieberman, our early Australopith ancestors had less developed arches in their feet. Homo sapiens, by contrast, has evolved a strong, large arch that we use as a spring when running.

"Our feet were made in part for running," Lieberman says. But as he and his co-authors write in Nature: "Humans have engaged in endurance running for millions of years, but the modern running shoe was not invented until the 1970s. For most of human evolutionary history, runners were either barefoot or wore minimal footwear such as sandals or moccasins with smaller heels and little cushioning."

For modern humans who have grown up wearing shoes, barefoot or minimal shoe running is something to be eased into, warns Lieberman. Modern running shoes are designed to make heel-striking easy and comfortable. The padded heel cushions the force of the impact, making heel-striking less punishing.

"Running barefoot or in minimal shoes is fun but uses different muscles," says Lieberman. "If you've been a heel-striker all your life you have to transition slowly to build strength in your calf and foot muscles."
In the future, he hopes, the kind of work done in this paper can not only investigate barefoot running, but can provide insight into how to better prevent the repetitive stress injuries that afflict a high percentage of runners today.

"Our hope is that an evolutionary medicine approach to running and sports injury can help people run better for longer and feel better while they do it," says Lieberman, who has created a web site, www.barefootrunning.fas.harvard.edu, to educate runners about the respective merits of shod and barefoot running.

Source:Science Daily 2010

Human Gait Adapted for Efficient Walking at the Cost of Efficient Running

Humans, other great apes and bears are among the few animals that step first on the heel when walking, and then roll onto the ball of the foot and toes. Now, a University of Utah study shows the advantage: Compared with heel-first walking, it takes 53 percent more energy to walk on the balls of your feet, and 83 percent more energy to walk on your toes."Our heel touches the ground at the start of each step. In most mammals, the heel remains elevated during walking and running," says biology Professor David Carrier.

"Most mammals -- dogs, cats, raccoons -- walk and run around on the balls of their feet. Ungulates like horses and deer run and walk on their tiptoes," he adds. "Few species land on their heel: bears and humans and other great apes -- chimps, gorillas, orangutans."

"Our study shows that the heel-down posture increases the economy of walking but not the economy of running," says Carrier. "You consume more energy when you walk on the balls of your feet or your toes than when you walk heels first."
Economical walking would have helped early human hunter-gatherers find food, he says. Yet, because other great apes also are heel-first walkers, it means the trait evolved before our common ancestors descended from the trees, he adds.
"We [human ancestors] had this foot posture when we were up in the trees," Carrier says. "Heel-first walking was there in the great apes, but great apes don't walk long distances. So economy of walking probably doesn't explain this foot posture [and why it evolved], even though it helps us to walk economically."
Carrier speculates that a heel-first foot posture "may be advantageous during fighting by increasing stability and applying more torque to the ground to twist, push and shove. And it increases agility in rapid turning maneuvers during aggressive encounters."
The study concludes: "Relative to other mammals, humans are economical walkers but not economical runners. Given the great distances hunter-gatherers travel, it is not surprising that humans retained a foot posture, inherited from our more arboreal [tree-dwelling] great ape ancestors, that facilitates economical walking."

Measuring the Costs of Different Modes of Walking and Running

Carrier conducted the study with Christopher Cunningham, a doctoral student in biology at the University of Utah; Nadja Schilling, a zoologist at Friedrich Schiller University of Jena, Germany; and Christoph Anders, a physician at University Hospital Jena. The study was funded by the National Science Foundation, Friedrich Schiller University of Jena and a German food industry insurance group interested in back pain.
The study involved 27 volunteers, mostly athletes in their 20s, 30s and 40s. Each subject walked or ran three different ways, with each step either heel-first, ball-of-foot first with the heel a bit elevated or toes first with the heel even more elevated.
In his lab, Carrier and colleagues measured oxygen consumption -- and thus energy use -- as 11 volunteers wore face masks while walking or running on a treadmill. They also walked on a "force plate" to measure forces exerted on the ground.
Part of the study was conducted at Anders' lab in Germany, where 16 people walked or ran on a treadmill as scientists monitored activity of muscles that help the ankles, knees, hips and back do work during walking and running.
Findings of the experiments included:
  • "You consume more energy when you walk on the balls of your feet or your toes than when you walk heels-first," Carrier says. Compared with heels-first walkers, those stepping first on the balls of their feet used 53 percent more energy, and those stepping toes-first expended 83 percent more energy.
  • "The activity of the major muscles of the ankle, knee, hip and back all increase if you walk on the balls of your feet or your toes as opposed to landing on your heels," says Carrier. "That tells us the muscles increase the amount of work they are producing if you walk on the balls of your feet."
  • "When we walk on the balls of our feet, we take shorter, more frequent strides," Carrier says. "But this did not make walking less economical." Putting the heel down first and pivoting onto the ball of the foot makes the stride longer because the full length of the foot is added to the length of the step. But that has no effect on energy use.
  • The researchers wondered if stepping first on the balls of the feet took more energy than walking heel-first because people are less stable on their toes or balls of the feet. But increased stability did not explain why heel-first walking uses less energy.
  • Stepping heel-first reduced the up-and-down motion of the body's center of mass during walking and required less work by the hips, knees and ankles. Stepping first onto the balls of the feet slows the body more and requires more re-acceleration.
  • Heels-first steps also made walking more economical by increasing the transfer of movement or "kinetic" energy to stored or "potential" energy and back again. As a person starts to step forward and downward, stored energy is changed to motion or kinetic energy. Then, as weight shifts onto the foot and the person moved forward and upward, their speed slows down, so the kinetic energy of motion is converted back into stored or potential energy. The study found that stepping first onto the balls of the feet made this energy exchange less efficient that walking heels-first.
  • Heel-first walking also reduced the "ground reaction force moment" at the ankle. That means stepping first onto the ball of the foot "decreases the leverage, decreases the mechanical advantage" compared with walking heel-first, Carrier says.
In sum, walking heel-first is not more economical because it is more stable or involves fewer, longer strides, but because when we land on our heels, less energy is lost to the ground, we have more leverage, and kinetic and potential energy are converted more efficiently.

Form and Function of the Foot

If heel-first walking is so economical, why do so many animals walk other ways?
"They are adapted for running," Carrier says. "They've compromised their economy of walking for the economy of running."
"Humans are very good at running long distances. We are physiologically and anatomically specialized for running long distances. But the anatomy of our feet is not consistent with economical running. Think of all the animals that are the best runners -- gazelles, deer, horses, dogs -- they all run on the ball of their feet or the tips of their toes."
When people run, why is there no difference in the amount of energy they expend when stepping first onto their heels versus the balls of their feet or toes?
The answer is unknown, but "if you land on your heel when you run, the force underneath the foot shoots very quickly to the ball of your foot," Carrier says. "Even when we run with a heel plant, most of the step our weight is supported by the ball of our foot. Lots of elite athletes, whether sprinters or distance runners, don't land on their heel. Many of them run on the balls of their feet," as do people who run barefoot. That appears to be the natural ancestral condition for early human runners, he adds.
"The important thing is we are remarkable economical walkers," Carrier says. "We are not efficient runners. In fact, we consume more energy to run than the typical mammal our size. But we are exceptionally economical walkers."
"This study suggests that one of the things that may explain such economy is the unusual structure of our foot," he adds. "The whole foot contacts the ground when we walk. We have a big heel. Our big toe is as long as our other toes and is much more robust. Our big toe also is parallel to and right next to the second toe."
"These features are distinct among apes, and provide the mechanical basis for economical walking. No other primate or mammal could fit into human shoes."


Reference:
  1. Cunningham, C. B., Schilling, N., Anders, C. and Carrier, D. R. The influence of foot posture on the cost of transport in humans. J. Exp. Biol., 213, 790-797
ScienceDaily (Feb. 12, 2010) 





Wednesday, 3 February 2010

Neolithic Amputation...anaesthetic and aseptic.


Scientists unearthed evidence of surgery carried out in ancient times during work on an Early Neolithic tomb discovered at Buthiers-Boulancourt, about 65km south of Paris. They found that a remarkable degree of medical knowledge had been used to remove the left forearm of an elderly man about 6,900 years ago. The patient seems to have been anaesthetised, the conditions were aseptic, the cut was clean and the wound was treated, according to the French National Institute for Preventive Archaeological Research .

The revelation could force a reassessment of the history of surgery, especially because researchers have recently reported signs of two other Neolithic amputations in Germany and the Czech Republic. It was known that Stone Age doctors performed trephinations, cutting through the skull, but not amputations. "The first European farmers were therefore capable of quite sophisticated surgical acts."

The discovery was made by C├ęcile Buquet-Marcon and Anaick Samzun, both archaeologists, and Philippe Charlier, a forensic scientist. It followed research on the tomb of an elderly man who lived in the Linearbandkeramik period, when European hunter-gatherers settled down to agriculture, stock-breeding and pottery. The patient was important: his grave was 2m long - bigger than most - and contained a schist axe, a flint pick and the remains of a young animal, which are evidence of high status. The most intriguing aspect, however, was the absence of forearm and hand bones. A battery of biological, radiological and other tests showed that the humerus bone had been cut above the trochlea indent at the end 'in an intentional and successful amputation'.

Mrs Buquet-Marcon said that the patient, who is likely to have been a warrior, might have damaged his arm in a fall, animal attack or battle, she said "I don't think you could say that those who carried out the operation were doctors in the modern sense that they did only that, but they obviously had medical knowledge," 

A flintstone almost certainly served as a scalpel. Mrs Buquet-Marcon said that pain-killing plants were likely to have been used, perhaps the hallucinogenic Datura. "We don't know for sure, but they would have had to find some way of keeping him still during the operation," she said. Other plants, possibly sage, were probably used to clean the wound. "The macroscopic examination has not revealed any infection in contact with this amputation, suggesting that it was conducted in relatively aseptic conditions," said the scientists in an article for the journal Antiquity.

The patient survived the operation and, although he suffered from osteoarthritis, he certainly lived for months, perhaps years, afterwards. Despite the loss of his forearm, the contents of his grave showed that he remained part of the community. "His disability did not exclude him from the group," the researchers said. The discovery demonstrates that advanced medical knowledge and complex social rules were present in Europe in about 4900 BCE, and that major surgery was likely to have been more common than we realised, stated Mrs Buquet-Marcon.

Image credit: Hulton