Short Heels Make Elite Sprinters Super Speedy: Longer Toes, Unique Ankle Structure Aid Sprinters

Longer toes and a unique ankle structure provide sprinters with the burst of acceleration that separates them from other runners, according to biomechanists.

"At the start of a sprint the only way a runner can speed up is through the reaction force that results from the action of leg muscles pushing on the ground," said Stephen Piazza, associate professor of kinesiology, Penn State. "Long toes provide sprinters the advantage of maintaining maximum contact with the ground just a little bit longer than other runners."

Piazza and his colleague Sabrina S. M. Lee, former Penn State graduate student now a post-doctoral fellow at Simon Fraser University, Vancouver, Canada, studied the muscle architecture of the foot and ankle to look at the differences between sprinters and non-sprinters.

They matched 12 collegiate sprinters with 12 non-athletes of the same height. They measured the distance between the heel and the end of the toes and used ultrasound imaging to measure the sliding of the Achilles tendon during ankle motion, from which the leverage of the tendon can be calculated.

"What we found was that the lever arms (distance between the tendon and center of rotation of the ankle) were significantly shorter -- about 25 percent shorter -- in sprinters," said Piazza, whose findings appeared recently in the Journal of Experimental Biology. "This difference might be explained by a tradeoff between leverage and muscle force-generating capacity."

Because the lever arms are shorter, the muscles shorten less for the same joint rotation. If muscles shorten less, they shorten more slowly, which helps them to produce greater force that more than compensates for the reduced leverage.

While there is little published work on foot shapes and sprinting, previous work on animals suggests that ostriches, greyhounds and cheetahs have feet built for sprinting.

To understand the kind of human foot that would produce a similar sprinting advantage, the researchers developed a simple computer model that could analyze the physiological data they had collected earlier.

"We wanted to see how much acceleration we could get out of the model when we changed the tendon lever arm and the length of the toes," said Piazza. "What we found is that when the Achilles tendon lever arm is the shortest and the toes are longest, we get the greatest acceleration."

Piazza cites other recent research suggesting that shorter toes in modern humans could be an evolutionary adaptation for efficient distance running.

"Maybe our ancestors with longer toes were better sprinters. Or maybe longer toes were selected for at a time when navigating in trees was more important and our toes became shorter as endurance running became more important for our survival," he added.

The Penn State researcher cautions that while the study could be a piece of the puzzle in determining who could potentially be a good sprinter, other physiological components such as body type, cardiovascular physiology and muscle fiber types should also be taken into account.

It is also unclear whether sprinting ability is congenital or whether training can influence the shape of bones in the foot.

"It is not too far-fetched to think that training can help accentuate the shape of the bone," said Piazza. "But if sprinters' skeletal characteristics were shown to be immutable, it would support the coaches' adage that sprinters are born and not made."

The National Science Foundation funded this work.

NASA's Fermi Telescope Detects Gamma Rays From 'Star Factories' In Other Galaxies

Nearby galaxies undergoing a furious pace of star formation also emit lots of gamma rays, say astronomers using NASA's Fermi Gamma-ray Space Telescope. Two so-called "starburst" galaxies, plus a satellite of our own Milky Way galaxy, represent a new category of gamma-ray-emitting objects detected both by Fermi and ground-based observatories.

"Starburst galaxies have not been accessible in gamma rays before," said Fermi team member Seth Digel, a physicist at SLAC National Accelerator Laboratory in Menlo Park, Calif. "Most of the galaxies Fermi sees are exotic and distant blazars, which produce jets powered by matter falling into enormous black holes. But these new galaxies are much closer to us and much more like our own."

Gamma rays are the most energetic form of light. Fermi has detected more than a thousand point sources and hundreds of gamma-ray bursts, but the satellite also detects a broad glow that roughly follows the plane of our galaxy. This diffuse gamma-ray emission results when fast-moving particles called cosmic rays strike galactic gas or even starlight.

Cosmic rays are hyperfast electrons, positrons, and atomic nuclei moving at nearly the speed of light. But, although Earth is constantly bombarded by these particles, their origin remains a mystery nearly a century after their discovery. Astronomers suspect that the rapidly expanding shells of exploded stars somehow accelerate cosmic ray particles to their fantastic energy.

"For the first time, we're seeing diffuse emission from star-forming regions in galaxies other than our own," noted Jürgen Knödlseder, a Fermi collaborator at the Center for the Study of Space Radiation in Toulouse, France. He spoke to reporters today at the 2009 Fermi Symposium, a Washington gathering of hundreds of astrophysicists involved in the Fermi mission and related studies. The meeting continues through Nov. 5.

Knödlseder revealed an image captured by Fermi's Large Area Telescope (LAT) of a star-forming region known as 30 Doradus within the Large Magellanic Cloud (LMC). Located 170,000 light-years away in the southern constellation Dorado, the LMC is the largest of several small satellite galaxies that orbit our own.

More stars form in the 30 Doradus "star factory" than in any similar location in the Milky Way. "The region is an intense source of gamma rays, and the diffuse emission we see with Fermi follows the glowing gas we see in visible light," Knödlseder explained.

The region lights up in gamma rays for the same reason the Milky Way does -- because cosmic rays strike gas clouds and starlight. But Fermi shows that the LMC's brightest diffuse emission remains close to 30 Doradus and doesn't extend across the galaxy. This implies that the stellar factory itself is the source of the cosmic rays producing the glow.

"Star-forming regions produce lots of massive, short-lived stars, which explode when they die," Digel said. "The connection makes sense."

"The tangled magnetic fields near 30 Doradus probably confine the cosmic rays to their acceleration sites," Knödlseder said.

Fermi's LAT sees diffuse emission from the starburst galaxies M82 and NGC 253, both of which were also seen this year by ground-based observatories sensitive to gamma rays hundreds of times more energetic than the LAT can detect. They do this by imaging faint flashes in the upper atmosphere caused by the absorption of gamma rays carrying trillions of times the energy of visible light.

"The core of M82 forms stars at a rate ten times greater than the entire Milky Way galaxy," said Niklas Karlsson, a postdoctoral fellow at Adler Planetarium in Chicago. He is also a member of the science team for VERITAS, an array of gamma-ray telescopes in Arizona that detected M82, which lies 12 million light-years away in the constellation Ursa Major.

"These very-high-energy gamma rays probe physical processes in other galaxies that will help us understand how and where cosmic rays become accelerated," Karlsson explained.

"Our sensitivity to gamma-rays -- both in space and on the ground -- has increased enormously thanks to Fermi and observatories like VERITAS," Digel said. "This is opening up the detailed study of high-energy processes in galaxies very close to home." NASA's Fermi Gamma Ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

Newly Discovered Ankylosaur Dinosaur Is 'Biological Version Of An Army Tank'

A husband and wife team of American paleontologists has discovered a new species of dinosaur that lived 112 million years ago during the early Cretaceous of central Montana.

The new dinosaur, a species of ankylosaur, is documented in the October issue of the Canadian Journal of Earth Sciences. Ankylosaurs are the biological version of an army tank. They are protected by a plate-like armour with two sets of sharp spikes on each side of the head, and a skull so thick that even 'raptors' such as Deinonychus could leave barely more than a scratch.

Bill and Kris Parsons, Research associates of the Buffalo Museum of Science, found much of the skull of the newly described Tatankacephalus cooneyorum resting on the surface of a hillside in 1997. Because the skull was 90% complete, it was possible to justify this fossil as a new species.

"This is the first member of Ankylosauridae to be found within the Early Cretaceous Cloverly Geologic Formation," said Bill Parsons, who characterized the fossil as a transitional evolutionary form between the earlier Jurassic ankylosaurs and the better known Late Cretaceous ankylosaurs.

The skull is heavily protected by two sets of lateral horns, two thick domes at the back, and smaller thickenings around the nasal region. "Heavy ornamentation and horn-like plates would have covered most of the dorsal surface of this dinosaur" said Bill Parsons.

"For years, Bill and Kris have been collecting fossils from a critical time in Earth's history, and their hard work has paid off," said Lawrence Witmer, professor of paleontology at Ohio University who was not involved with this study. "This is a really important find and gives us a clearer view of the evolution of armored dinosaurs. But this is just the first; I'm sure, of what will be a series of important discoveries from this team."

Parsons also illustrated the dermal armour of this new species based on the theory by Museum of the Rockies paleontologist John R. Horner that there was an outer keratinous sheathing on it as found in modern turtle shells and bird beaks. In his new reconstruction, Parsons suggests that Tatankacephalus exhibited complex and colorful patterns rather than the dull appearance suggested in earlier ankylosaur portraits. "According to Horner's theory, many other dinosaurs also had this kind of sheathing and also may have been diversely colored," said Parsons.

As to its name, the broad, short horns on the back of its skull resemble the horns found on a modern buffalo skull and Tatankacephalus loosely translates as 'Buffalo head.' Parsons also noted, "of course any further allusions to the city of Buffalo are completely intentional as well."