A Simon Fraser University study on how kangaroos use their tails as a 'fifth' leg is providing new insight into the diversity of biological movement, and specific insight into why we walk the way we do.
Published today in the Royal Society journal Biology Letters, the study, led by professor Max Donelan of SFU's Locomotion Laboratory, found kangaroos, commonly viewed as hoppers, move with a "pentapedal" gait, planting their tails on the ground in combination with their front and hind legs.
"We measured the forces the tail exerts on the ground and calculated the mechanical power it generates, and found that the tail is responsible for more propulsive force than the front and hind legs combined," explains Donelan, an associate professor in the Department of Biomedical Physiology and Kinesiology (BPK).
"It also generates almost exclusively positive mechanical power, performing as much mechanical work as a human leg when walking at the same speed. Their muscular tail is used to propel and power their motionjust like a leg."
Measurements were carried out at the University of New South Wales in Sydney Australia back in 2001, but the researchers were only just recently able to analyze them properly, thanks to innovations by Donelan's collaborator, Dr. Shawn O'Connor.
"One of the central findings of our human walking research is that it is very important to time the push-off of your back leg to make walking less effortful," says Donelan, founder and scientific advisor to Bionic Power. The university spin-off company develops energy harvesting technology for those who depend on portable power.
"People recovering from strokes or spinal cord injury can't do this as well because their legs are partially immobilized, making walking more effortful."
Kangaroos, meanwhile, have very short front legs that can't be used to push off. "The timing and position of the tail, on the other hand, is perfect," h
|Contact: Max Donelan|
Simon Fraser University