This is an archived article.

September 4, 1996

MR technique for analyzing rattlesnake tail muscles can also be used to study muscle tone and function in the elderly

When a rattlesnake shakes its rattle ominously to frighten off its enemies, its tail muscles accomplish a feat that few other muscle groups in the animal kingdom — including human muscle — can achieve.

While almost all muscle tissue is either fast-twitch (like the sprinter’s) or slow- twitch (like the endurance runner’s), magnetic resonance studies at University of Washington Medical Center show that the rattlesnake’s tail muscles can sustain rapid firing over a long period of time, with great economy of energy.

If the best marathon runners could contract their muscles at the rate the rattlesnake does, and expend as little energy, they could run an entire 26-mile race in just eight and a half minutes.

So estimates UW researcher Dr. Kevin E. Conley who, with co-author Dr. Stan L. Lindstedt of Northern Arizona University, reports on their study of rattlesnake muscle function in the Sept. 5 issue of the journal Nature.

“We use the rattlesnake as a model for understanding muscle function,” said Conley, who is associate professor of radiology and adjunct associate professor of bioengineering at the UW. “It’s a very simple muscle system, with properties that are uniform throughout the muscle, unlike human muscle, which is very heterogenous. It’s getting us a long way toward understanding human muscle systems.”

To measure the compounds involved in energy supply and demand while the muscles are actually working, the researchers employed non-invasive magnetic resonance spectroscopy on a total of 10 live rattlesnakes, prompting the reptiles to rattle merely by walking into the room, or by administering mild electrical stimulation similar to that used to make human muscles contract. Producing sound is generally one of the most costly activities in animals, in terms of energy expenditure.

But Conley notes that, in the rattlesnake, energy expenditure is kept to a minimum because the muscle tissue of the snake’s tail has a much lower percentage of actual contracting muscle fiber compared to almost all other muscle tissue throughout the animal kingdom.

“It’s a good model for sustained muscle performance,” said Conley, who has used similar MR analysis to help develop training protocols for older adults who lose muscle strength, and thus functional performance, as they age.

In earlier studies, Conley and colleagues showed how magnetic resonance imaging and magnetic resonance spectroscopy can be used to analyze muscle function in humans, especially in the elderly who lose muscle mass and function. The non-invasive techniques determine the capacity of the muscle and its contribution to the performance of the whole body.

The studies involved elderly women who participated in stair-step training wearing weighted backpacks, three times a week for a year. They were compared to a similar group of women who did not receive such training. The studies showed that a moderate training program that integrates a variety of muscle activities results in increased muscle strength and physical performance of the lower body, improving balance and function, and decreasing the chance of falls.

Contacts: Dr. Kevin Conley, (206) 543-3763 or kconley@u.washington.edu
Laurie McHale, (206) 543-3620 or lmchale@u.washington.edu
C301 Health Sciences Center
Box 356345
Seattle, Washington 98195
(206) 543-3620
Fax (206) 685-3333