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Do the Locomotion

Nov. 13, 2006
By Anita Martin

Animal locomotion sparked the curiosity of Aristotle in 350 B.C., inspiring three books on the subject of biomechanics. Leonardo da Vinci analyzed human anatomy, the gaits of horses and the flight of birds in the early 16th century.

New Professor Lecture Series continues

Steve Reilly presented "Locomotor Biomechanics and Muscle Function: Cool Things You Didn't Know about Walking, Running and Breathing"  in November. His lecture, which discussed the biomechanics and evolutionary implications of everyday movement, was the second in the College of Arts and Sciences New Professor Lecture Series.

The College of Arts and Sciences New Professor Lecture Series was developed to recognize the scholarly achievements of all eight Arts and Sciences faculty recently promoted to the rank of professor. Each lecture will take place in campus venues, followed by a reception.

Alumni can watch the lectures through a live feed via the internet, using streaming video technology. To watch lectures live, go to http://streaming.cns.ohiou.edu/CAS during each lecture. Video and audio (MP3) archive will be available on the college's Web site in the future.

The next lecture, "Fighting with Friends: the Dynamics of Coalition Warfare," will feature the research of Patricia Weitsman, professor of political science. The lecture will take place at 4:10 p.m. on Monday, Jan. 1, in Irvine Auditorium.

More recently, Professor of Biological Sciences Steve Reilly brought us up to speed, so to speak, on our understanding of the biomechanics of locomotion.

In his lecture "Locomotor Biomechanics and Muscle Function: Cool Things You Didn't Know About Walking, Running, and Breathing," Reilly said that in the field of biomechanics, "everybody goes out and studies the big, weird, wacky animals like humans, dogs, horses and kangaroos."

And that's just where his lecture started. Reilly slapped a black and white paper "marker" on his hip and demonstrated the up-and-down movement of human hips during walking. We have known for some time that this reverse pendulum-like movement appears in all upright animals and that it saves us energy.

When running, we save energy by virtue of a "spring" mechanism, concentrated mostly in our elastic Achilles' tendons. For example, Dean Ben Ogles of the College of Arts and Sciences, a self-proclaimed "social runner" saves about 30 percent of the cost of locomotion via the elasticity of his tendons.

Before Reilly, we knew that "freaky" upright walkers use pendulum and spring designs to walk and run, but we didn't know about the rest of the animal kingdom. Reilly focuses his work on the underrepresented majority of locomotors out there, those that move from the more common "sprawling" limb postures – namely: amphibians, reptiles and small mammals.

Obtaining this missing data for all tetrapods, or four-legged beasts, was an exercise in comparative evolutionary studies. According to Reilly's doctoral candidate Mike Jorgenson, biomechanics and morphology -- the study of the form and structure of organisms -- are "tools one uses to look at evolutionary inferences and relationships."

In Reilly's lab, housed in the new Life Sciences Building, lizards and small mammals run across "force plates," springy surfaces built by Reilly and his students that measure ground forces. Next, that data runs through virtual instruments, also designed by Reilly and students, which apply basic physics equations to calculate velocity, acceleration, and kinetic and potential energy profiles.

Their new data for lizards, salamanders, tuataras (an Australian reptile) and alligators showed, in fact, all of the sprawlers exhibit pendulur and spring mechanics. From this we confirm that all tetrapods can walk and run (except turtles, whose bulky shells impede their locomotor mechanics).

"That's important, because if everyone can do it now, that means that the first tetrapods that crawled onto land nearly 400 million years ago could also walk and run," Reilly said.

After that conclusion, Reilly shifted the focus of his presentation to the mechanism of breathing and its relation to running. His research looks at mammals, the only class of animals with a diaphragm to help "suck" in air during inhalation. Exhalation, despite popular medical dogma, remained unconfirmed.

"If you look it up in any medical text, or ask any doctor, you'll be told that your belly muscles contract to help you exhale," Reilly said. "But, those belly muscles are like a paint job, they're so thin. Nobody wanted to go to the trouble of measuring these muscles to get the data to prove it."

That is, until Reilly and his colleagues tackled the subject.  In their laboratory, they painstakingly attach ultra-thin wires into the superficial abdominals of possums, rats and mice. The critters then run along a treadmill as a fine wire electromyography machine detects and amplifies muscle contraction. Meanwhile video fluoroscopy records x-ray images of the rodent mini-marathons to visualize the diaphragm moving during breathing.

"We found out that large animals, like the big possums and like us, have mild tonus (contraction) in the gut at rest, meaning we're exhaling slightly and smoothly with our belly muscles," Reilly said. "When we run, our belly muscles kick in to actively exhale with each step, just as the popular medical dogma suggested."

Then they wired up very small mammals. The team was shocked to realize that, during rest, very small mammals actively breathe a rapid-fire ten breaths per second. "At first I thought: 'there must be some interference,'" Reilly said. But each time the results confirmed this swift breathing rate. This explains the scientific conundrum of why very small rodents seem to constantly vibrate in your hand, Reilly joked.

When the small mammals hit the treadmill, they run at one speed only: five steps per second. Meanwhile, their breathing never changes.  Instead of the one-to-one breath-step that we enjoy, smaller mammals like mice endure a panting two breaths per step. And because they cannot increase their oxygen input to match their level of exertion, small mammals tire quickly.

It all goes back to something called natural frequency, Reilly explained. Everything, from tuning forks to buildings to living things, has one. When we run at full speed, our breathing matches our steps to form such a natural frequency. Smaller animals, however, breathe at their natural frequency all of the time.

The conclusion, according to Reilly: "It's not cool to be small if you want to be a real killer runner."

Like their findings on walking and running, the implications of this discovery go back to the evolution of all mammals. The first mammals running around the feet of dinosaurs were roughly the size of an ordinary paper clip.

"Once we got out of the size bottleneck, mammals could become much better runners, climbers, diggers, swimmers, and all that stuff," Reilly said. "When the dinos left town, the mammals got bigger and changed, and here we are with all the wild and wonderful locomotor modes you see today."

After earning his Ph.D. in zoology at Southern Illinois University, Reilly completed post-doctorate research in functional morphology at the University of California, Irvine. At Ohio University, where his interests shifted to locomotion, Reilly teaches courses in comparative vertebrate anatomy, ecology and comparative biology.

Reilly will be the first director of the new Ohio Center for Ecology and Evolutionary Studies at Ohio University.  Between March and June 2007, Reilly will be conducting locomotion research in Australia, during which time, Associate Professor of Biological Sciences Willem Roosenburg will step in as the center's interim director.

The Center for Ecology and Evolutionary Studies will begin program development early in 2007. They aim to promote Ohio University's strength in ecology and evolutionary biology at with new graduate research fellowships and a new Undergraduate Research Immersion Program (UGRIP), and by formalizing a new campus science seminar series.


Anita Martin works in the College of Arts and Science Dean's Office.

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Published: Jan 3, 2007 9:35:38 AM
 
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