We all know about rattlesnakes, and most of us have heard the sound
they make--or at least a recording of that sound. The frequency of the
sound we hear can be as high as 90 hertz, which means that the snake is
shaking the tip of its tail 90 times per second. By comparison, the
wings of a hummingbird are moved only about 40 times per second, and if
you have heard hummingbirds around a feeder you know that sound has a
very low pitch. The most rapid speed humans can move their muscles is
about eight times per second--over ten times slower than the
rattlesnake. Not only is the frequency an issue, but the snake can keep
up his rattle for a very long period of time, where human muscles
fatigue very quickly. Studies of how the rattlesnake does this have led
to some interesting possibilities as far as exercise equipment for
A rattlesnake rattle is dead tissue. The snake makes the sound by twitching sets of small muscles on either side of its tail. It had been thought that muscle contractions pulled the tail tip first one way and then the other, but research has shown that the muscles extend or lengthen rather than contract or shorten. The muscle on one side lengthens and pushes the rattle one way. The muscle on the other side is contracting and absorbing that energy. When it lengthens it pushes the tail tip the other way and the energy and forces are reversed.
It takes less energy to extend a muscle than to contract it. Going down into the Grand Canyon requires less energy than coming out. The muscles exert more force however because of the inertia requirements of stopping the weight that is being lowered. Even though we are supporting the same weight, the lengthening of a muscle produces about twice as much force as shortening it.
Most human exercise programs are designed to make muscles stronger. Researchers at Northern Arizona State University have taken the rattlesnake rattle, and designed exercise equipment that uses this principle. Physiologist Stan Lindstedt built an exercise bike with electrically powered pedals that run backwards so the patients muscles must resist the force. When elderly patients tried this device, their muscle mass increased as did their balance. Members of a high school basketball team extended their jumping ability a couple of inches (8 percent) by using the same equipment.
In our day of fancy exercise equipment, it is interesting to know that the most modern exercise machine is designed by copying the engineering of the ancient reptile--the rattlesnake. The original engineer must have been infinitely brilliant.
Reference: National Wildlife, February/March 2008, page 14.
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