June 24, 2009
Research Team Explores Acceleration Of Four-Legged Animals
Researchers have shown that the acceleration of four-legged animals appears to be limited by their need to avoid tipping upward, thus losing traction as their legs miss the ground, BBC News reported.
In the past, it was assumed that acceleration was only limited by the animals' muscle power.This "wheelie" avoidance is the limit at low speeds, according to the research published in Biology Letters.
The research team showed that higher speed acceleration is capped by the amount of power in the muscles.
Team member Sarah Williams of the University of Liverpool explained that if your front end comes up - if you 'wheelie' - you then lose purchase with your front limbs on the ground.
Therefore, if you then continue to accelerate, you've got nothing preventing you from flipping over backwards, she added.
Williams told BBC News that her co-workers working in a similar area had noted that when lizards accelerate they actually run bipedally (on two legs), and that brought around the theory that perhaps this 'wheelie-ing' might be limiting whether they could accelerate any further.
Williams decided to lead a team at the Royal Veterinary College in London to explore if the acceleration of animals like polo ponies and greyhounds were limited because of their avoidance of this wheelie-ing phenomenon.
They recorded measurements of leg length and the distance from hip or shoulder to the center of mass from ponies and greyhounds in order to develop a mathematical model to match the "pitch avoidance" that they would undertake to keep them from wheelie-ing.
High-speed camera footage of the animals was employed to determine their speeds and accelerations. The team found that the animals did not reach the theoretically possible accelerations when running.
Williams explained that at those early stages of the acceleration, this pitch limit or wheelie-ing prevented them from reaching such speeds.
But they noted that this constraint did not operate once the animals got up to a reasonable speed.
The pitch limit appears to be overridden by an additional limit at higher speeds.
She explained this as the amount of power an animal can produce with its muscles, or the power its engine can produce.
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