Posts tagged South African
CU research propels “Blade Runner” to Olympics
0July 11, 2012
University of Colorado Boulder researchers will be watching closely when South African bilateral leg amputee and sprinter Oscar Pistorius, dubbed “The Blade Runner,” makes his way to the starting block for the 400-meter sprint in the 2012 London Olympics.
Professors Rodger Kram and Alena Grabowski of the integrative physiology department have been involved in several studies analyzing the performance of amputee athletes, including Pistorius, who use blade-like, carbon fiber leg prostheses in track events. In 2007, Pistorius was barred from international competition by officials from the International Association of Athletics Federations, or IAAF, who ruled his Cheetah Flex-Foot leg prostheses conferred him an advantage over other runners.
Barred from competition, then exonerated
The decision was based in large part on a German study commissioned by the IAAF. However, data presented in April 2008 by a team that included Kram and Grabowski to the Court of Arbitration for Sport in Lausanne, Switzerland — an international group set up to settle disputes in sports — showed Pistorius gained no physiological advantage from the Cheetah prostheses over competitors. The team’s evidence and testimony played a key role in overturning the decision, allowing Pistorius to compete in able-bodied events.
The Blade Runner good to go
“The methodology of the German study that involved measuring Oscar’s oxygen consumption while running was flawed,” said Kram, who has been measuring the oxygen consumption of runners since 1983. “When we had a chance to properly measure Oscar we found that while he is quite economical in oxygen consumption compared to your average Joe, his values are well within what would be expected for a high-caliber athlete.”
At the arbitration hearings in Switzerland, Kram also argued that if a prosthetic device provides a mechanical advantage, it would very likely provide an energetic or physiological advantage. “Since there is no energetic advantage, it infers that the prostheses do not provide a mechanical advantage either,” said Kram.
Another chance
Although Pistorius subsequently failed to make the 2008 Olympic team, he was selected by South Africa’s Olympic Committee last week to run in both the individual 400 meters and a leg of the 4×400 meter relay in the 2012 Olympic Games in London, which begin on July 27. “I was delighted that Oscar was selected,” said Kram. “I was sure he’d be named to the 4×400 meter relay, but being named to the 400-meter individual event was a surprise.”
Since 2008, the research team involving CU-Boulder has continued its studies. In a 2010 study led by Grabowski, researchers used force-measuring treadmills to analyze the biomechanics of unilateral amputees — those with one amputated leg — over a wide range of running speeds. The team found the force produced by the prosthetic, carbon fiber leg was 9 percent less than that of the unaffected leg. “Applying force to the ground is crucial in sprinting events,” said Grabowski.
“We inferred that running-specific prostheses impair force generation and likely limit top sprinting speed,” said Grabowski, who received her doctorate under Kram in 2008 and recently returned to CU-Boulder as a research faculty member after doing postdoctoral work at the Massachusetts Institute of Technology. Other authors on the 2010 paper included Kram, Craig McGowan of the University of Idaho, William McDermott of the Orthopedic Specialty Hospital in Murray, Utah, and Hugh Herr of MIT.
In a 2012 paper by the same group and led by McGowan, the leg stiffness of Paralympic sprinters with both unilateral and bilateral leg amputations was compared to non-amputee sprinters across a range of speeds. The team found leg stiffness remained constant or increased with speed in non-amputees but decreased in sprinting amputees.
“During running, the leg behaves much like a spring, and the stiffness of the leg greatly influences the overall mechanics of the runner,” said Grabowski. “The study indicates that the prosthetic device limits the ability of a sprinter to change their leg stiffness during running.” In the future, she said, researchers may be able to design a prosthetic device with “adaptive stiffness” that would more accurately emulate the mechanics of a biological ankle during sprinting.
Research fueled by veterans needs
Grabowski, whose work is funded by the Veterans Administration, is particularly interested in designing better prosthetic ankle devices for military veterans or those on active duty who have undergone amputations. In collaboration with the Denver Department of Veterans Affairs, Grabowski is beginning a research effort to further develop battery-powered ankle-foot prostheses for walking and running. Such prostheses have the potential to restore mobility to users similar to the mobility they had prior to amputation, she said.
The research team is interested in locating potential test subjects in the Denver-Boulder area with leg amputations to participate in lab studies. “CU-Boulder is actively pursuing research that aims to improve the lives of amputees, particularly veterans and current military personnel,” she said. Potential study candidates can contact Grabowski at Alena.Grabowski@colorado.edu.
Research in Kram’s Locomotion Laboratory on the CU-Boulder campus goes far beyond athletics. Collaborating faculty and students are targeting the energetic costs of walking, including uphill and downhill walking in older adults; the energetics of passive cycling to treat and prevent obesity and heart disease; and studies on animal locomotion, including kangaroos, tortoises and elephants.
For more information on the CU-Boulder Locomotion Laboratory visit http://www.colorado.edu/intphys/research/locomotion.html. For more information on CU’s integrative physiology department visithttp://www.colorado.edu/intphys/.
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ANCIENT HOMINID MALES STAYED HOME WHILE FEMALES ROAMED, SAYS CU STUDY
0June 1, 2011
by Ron Baird, news editor
in News
The males of two bipedal hominid species that roamed the South African savannah more than a million years ago were stay-at-home kind of guys when compared to the gadabout gals, says a new high-tech study led by the University of Colorado Boulder.
The team, which studied teeth from a group of extinct Australopithecus africanus and Paranthropus robustus individuals from two adjacent cave systems in South Africa, found more than half of the female teeth were from outside the local area, said CU-Boulder adjunct professor and lead study author Sandi Copeland. In contrast, only about 10 percent of the male hominid teeth were from elsewhere, suggesting they likely grew up and died in the same area.
“One of our goals was to try to find something out about early hominid landscape use,” said Copeland, who also is affiliated with the Max Plank Institute for Evolutionary Anthropology in Leipzig, Germany. “Here we have the first direct glimpse of the geographic movements of early hominids, and it appears the females preferentially moved away from their residential groups.”
A paper on the subject is being published in the June 2 issue of Nature. Co-authors included CU-Boulder anthropology Professor Matt Sponheimer, Darryl de Ruiter from Texas A&M University, Julia Lee Thorp from the University of Oxford, Daryl Codron from the University of Zurich, Petrus le Roux from the University of Cape Town, Vaughan Grimes of Memorial University-St. John’s campus in Newfoundland and Michael Richards of the University of British Columbia in Vancouver.
The new study results were somewhat surprising, said Copeland. “We assumed more of the hominids would be from non-local areas, since it is generally thought the evolution of bipedalism was due in part to allow individuals to range longer distances,” she said. “Such small home ranges could imply that bipedalism evolved for other reasons.”
The team used a high-tech analysis known as laser ablation, zapping the hominid teeth with lasers to help them measure isotope ratios of strontium found in tooth enamel in order to identify specific areas of landscape use. A naturally occurring element, strontium is found in rocks and soils and is absorbed by plants and animals.
Since unique strontium signals are tied to specific geological substrates — like granite, basalt, quartzite, sandstone and others — they can be used to reveal landscape conditions where ancient hominids grew up, said Copeland. “The strontium isotope ratios are a direct reflection of the foods these hominids ate, which in turn are a reflection of the local geology.”
The study was funded by the National Science Foundation, the Max Planck Society, a University of Colorado LEAP Associate Professor Growth Grant and the University of Colorado Dean’s Fund for Excellence.
“It is difficult enough to work out relations between the sexes today, so the challenges in investigating the ways that male and female hominids used the landscape and formed social groups over a million years ago are considerable, to say the least,” said CU-Boulder’s Sponheimer. “Disembodied skulls and teeth are notoriously poor communicators, so the real difficulty with a study like this is finding new ways to make these old bones speak.”
Strontium isotope signatures are locked into the molars of mammals by the end of tooth enamel formation — for the hominids, probably at about eight or nine years old when they were traveling with their mothers. The Sterkfontein and Swartkans cave systems that yielded the teeth are less than a mile apart and dominated by a sedimentary carbonate rock known as dolomite, which has a distinct strontium signal, she said.
The team tested 19 teeth dating from roughly 2.7 to 1.7 million years ago from both Australopithecus africanus and Paranthropus robustus individuals from the two caves, which are well known for yielding valuable scientific data on hominid evolution.
Because the male hominids, like male humans, were larger than the females, the team used the size of individual molars to determine which were most likely from males or females, said Copeland. They also compared them to teeth and jaw fossils recovered from five early hominid sites in South Africa.
Both Paranthropus robustus and Australopithecus africanus were part of a line of close human relatives known as australopithecines that included the Ethiopian fossil, Lucy, estimated to be some 3.2 million years old and regarded by many as the matriarch of modern humans. While Australopithecus africanus may be a direct ancestor of modern humans, Paranthropus robustus and its close relative, Paranthropus boisei, both dead-ended on a side branch of the hominid family tree for reasons still unknown.
The female dispersal pattern believed seen in the two hominid groups is similar to that of many modern humans, chimpanzees and bonobos, said Copeland. But it is a dispersal pattern unlike most other primates — including gorillas — where the females stay with the group they are born into and the males move elsewhere. “This study gets us closer to understanding the social structure of ancient hominids, since we now have a better idea about the dispersal patterns,” she said.
The team also used laser ablation to zap 38 fossilized teeth of baboons, antelope, and small, rodent-like creatures known as hyraxes that lived in the same area at about the same time as the two australopithecine species under study. The results showed nearly all of the mammal teeth were local, implying such groups had relatively small home ranges, much like the australopithecine males, said Copeland.
While Sponheimer said the study could be taken as support for the position that bipedalism arose for reasons other than improved locomotion, the data might also indicate that many hominids simply preferred to live on dolomite substrates where caves would have been abundant. “I’ve never thought of these early male hominids as the quintessential cavemen, but the potential use of caves at this early time period is something worth considering.”
In addition, the team analyzed more than 170 modern plants and animals within a 30- mile-radius the two cave systems, sampling 11 different geological substrates. The minimum distance from the cave systems to non-local geology areas is about two miles to the southeast, four miles to the northwest, and more than 20 miles each in northeast and southwest directions, said Copeland. It is still not clear where the roaming female australopithecines identified in the study spent their formative years, she said.
