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January 3, 2011

Running A Fowl

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  Energetics of Walking and Running

Slo-motion video of the running guinea fowl

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For those who take a daily jog, running is second nature. But for one scientist, it's not so simple. In this ScienCentral News video, running is for the birds.


With the summer Olympics in Athens fast approaching, track athletes around the world are hitting the treadmill to get their legs in top shape. But in a small room on the fourth floor of a building on the Northeastern University campus, a team of helmeted guinea fowl are hitting the treadmill for a different reason.

Richard Marsh, biology professor at Northeastern University, is using them to discover precisely where every last bit of energy is being used when they run. Implications down the road range from helping people with walking or running abnormalities to enhancing the performance of competitive runners.

For the past ten years biologists have been going on the assumption called the "force hypothesis" put forth 14 years ago by Dick Taylor. The theory stated that almost all of the energy used while running is expended while the foot is on the ground, and that bringing the other leg forward requires very little energy.

“The estimates coming out of Dick Taylor’s lab…essentially suggested that it was insignificant, that it was so small that it didn’t show up in the measurements that he was making,” says Marsh. "So our study was designed to test that by trying to divide the cost of when the foot’s on the ground from the cost when the leg is off the ground and the limb is swinging through the air.”

guinea fowl on treadmill 2
He used helmeted guinea fowl, which are actually good models when it comes to studying human running. "I picked birds to work on to study this problem because they run on two legs, like humans do, and they’re the only other group of animals across the animal kingdom that really has been successful at that kind of two-legged locomotion," Marsh says. "It is true that the leg of a bird does have a somewhat different design than the human leg. However, the basic mechanisms of the way the walk works and the way running works are actually quite similar despite the differences in design.”

Marsh injected tiny colored microspheres into the fowl's circulatory systems, and had them run on a treadmill. The microspheres showed him which leg muscles required the most blood flow during the run, which indicates how much energy each muscle used up. "The way blood flow is distributed is according to demand," he says. "So, if a particular muscle increases the amount of energy it’s using, then more blood is sent to that muscle."

Marsh reported in the journal Science that swinging the leg forward actually takes about 25 percent of the total energy needed to run, much more than previously thought. He says this new knowledge can lead to better understanding of how to rehabilitate people with compromised leg function.

“If you don’t have a good idea of the way the normal locomotion works and what the function of all the muscles are, it’s difficult to sort of model that and figure out how to fix the abnormal problem.”

legs of guinea fowl
Marsh can use the same technique to target individual muscles in the leg and get more specific information on all the important muscles involved in running.

"So we can pick a muscle, say a big muscle that’s consuming fifteen percent of the energy, and say, 'Okay, that’s obviously one of the most important muscles in running'," he says. "And we can target that muscle for further studies to figure out what it’s doing mechanically in the stride that makes it consume so much energy.”

Eventually such information could lead to insights that benefit athletes. But for now Marsh is happy to continue his basic research, and maybe run a-fowl of a few more laws of nature.

Marsh's work, which appeared in the January 2. 2004 issue of Science, was funded by the National Institutes of Health.

       email to a friend by Brad Kloza

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