OREGON STATE UNIVERSITY

A scientific look at the tortoise and the hare

12/28/1998

CORVALLIS - Humans who want to run more effortlessly ought to stride like a turkey.

High jumpers who want to clear the bar with room to spare should definitely be training with frogs, who get far more length on their jump than their musculature should allow.

But for those of us who seem to spend all our time running hard and getting nowhere, take heart. We use our locomotor energy much more efficiently than mice.

Those findings and a number of others are the result of groundbreaking, published research on the comparative physiology and locomotor function of different animal species - including humans - by Thomas Roberts, an assistant professor of zoology at Oregon State University. Although animals of all types have been running, jumping and scurrying since the dawn of time, scientists are only now determining with any scientific accuracy just how they get from point A to B.

"We're trying to understand how locomotor function works from the cellular level on up," Roberts said. "Information such as this will be of value for some human health issues, such as gait dysfunction or athletic training. But right now there's still a great deal we don't understand about how animals move and why they function the way they do."

In that quest, Roberts has studied everything from the scurrying of mice to the respiration of African elephants, fitted out with masks and other instruments over their huge trunks to help analyze oxygen consumption and metabolic rate.

Scientists have known for some time that large animals such as an elephant can move their body mass far more efficiently than small animals such as an ant or mouse, using such comparisons as the amount of energy used to move a gram of mass one meter. But now the subtleties of movement are also starting to become more clear. Such techniques as the surgical implantation of sensors in the legs of a turkey running on a treadmill help reveal their secrets of motion.

Roberts and his colleagues, for instance, discovered that turkeys have a passive force mechanism in their stiff, calcified tendons - those stringy things in a turkey leg that often make it one of the less desirable cuts on a Thanksgiving dinner table. These tendons work sort of like a pogo stick snapping back after a jump, so the muscle itself doesn't have to provide all the work needed in locomotion.

"This is a very economical way to move," Roberts said. "Similar mechanisms probably work in humans and other bipedal animals. It may well be that some of the most energy-efficient human runners have tendon 'springs' that operate more effectively."

Some researchers in the past, in fact, thought that because of mechanisms such as this that two-legged animals should use less energy to move a given amount of body mass than four-legged animals.

"There's some logic to that theory," Roberts said. "Generally, large bipedal animals have longer legs with slower steps, and slow muscle fibers use less energy compared to the rapid scurrying of a smaller animal such as a mouse. But we found that bipeds have longer muscle fibers in their longer legs and must use more muscle, and we confirmed there's no inherent energy advantage to having two legs."

And then there are some of the real mysteries of nature, Roberts said, such as frogs, which some of his colleagues at Northeastern University have analyzed.

"If you look at the power available in the muscle of a frog and the length they can jump, they simply don't match," Roberts said. "Without other mechanisms at work a frog should not be able to jump as far as it does. In some the power generated is seven times the amount of muscle energy available."

What's actually happening, he said, is that some type of a "catch mechanism" appears to be at work in a frog's legs, allowing the muscles to stretch the leg tendons before any actual movement. Then, like a compound bow being released, the muscles and contracted tendons release all their energy at once.

"Frogs are designed for super acceleration more so than most other animals," Roberts said. "It's very remarkable the way their hind limbs have been optimized for this purpose."

Research such as this, Roberts said, will continue to help explain how animals move, what forces and mechanisms are at work and perhaps how they can be improved upon.

But efficiency of movement is not all there is to survival and prosperity, he said. And unlike the fable of the tortoise and the hare, plodders don't always win the race in the end.

"It seems likely that dinosaurs were the fuel economy champions of all time," Roberts and other researchers wrote in one study. "An ant may have a cost of locomotion 1,300 times greater than that of a large dinosaur. But ants are one of the most successful living animals groups in the world, and dinosaurs are extinct."