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Miracle Muscles : UCI Researchers Seek a Pill to Manipulate Growth and Stimulate Brawn Without Exercise


Pump iron for a month and, presto, your muscles get stronger.

Take to your La-Z-Boy for a month and your muscles go soft.

Everyone knows this happens, but no one knows exactly why. Why should you have to work to keep your muscles in shape? Why can't you relax and take a pill that duplicates two hours at the gym?

The surprising answer is: One may be on the way. Depending on which scientist you ask, it's just around the corner or it's 40 years away. But researchers agree they are closing in on the most basic, biological processes by which muscles decide whether to become stronger or weaker, quicker or slower.

Researchers are already beginning to manipulate the process. One chemical administered to laboratory rats duplicates some effects of daily workouts.

Does this mean that someday couch potatoes can look like Arnold Schwarzenegger? Probably not, says Kenneth M. Baldwin, professor of physiology and biophysics at UC Irvine and a leading researcher in the field.

But it does mean that the muscles of people with cancer and AIDS may not become so debilitated. And it might mean that ordinary people, who typically become sedentary and start weakening around age 60, can enjoy a stronger, less accident-prone old age.

But first in line to benefit are the people who have paid for so much of the research: the National Aeronautics and Space Administration.

Since the early days of space flight, they and their Russian colleagues have been trying to prevent the weakened muscles caused by the zero gravity of space. Early Soviet cosmonauts, the first to be aloft for long periods, sometimes could not even stand up after returning to Earth.

Trial-and-error experiments with muscle-taxing space suits and exercise equipment have yielded only slight gains. Baldwin--who has a 10-year NASA research grant and serves on three NASA science advisory committees--and other researchers have taken a different approach. They are studying how muscles work at their most basic level in hopes of isolating the process that keeps human muscles strong so they can duplicate it with safe drugs.

They say they are closing in.

They have discovered that muscles react not only to the amount of stress placed on them but to the type of stress, rapid or slow. Somehow these distinctions are transmitted to the genes in muscle cells, which then produce the appropriate kinds of muscle fibers.

The muscles become not only stronger or weaker but can change their very character. They may switch, say, from muscles with stamina and efficiency to muscles that provide short bursts of power and speed. Muscle research today is concentrating on just what signals make these changes take place, and, to find the answers, researchers are looking down to the level of the muscles' molecules.

You know what your muscles look like if you have ever examined a beefsteak. They are not a solid mass but a dense package of thin, fleshy layers.

View one of these layers through a very high-powered microscope and you can see the actual engines of the muscle--the millions upon millions of muscle filaments. Each is composed of short chains of protein molecules called myosin and actin, which together provide all of the muscle's movement and force.

The actin chain lies atop the myosin chain like a sliding hatch. When the muscle fiber is relaxed, the hatch lies "open," and the two chains are at their greatest combined length. But when the myosin receives the power command, it pulls the hatch "closed." That shortens the combined length of the two chains and provides the filament's tiny share of the muscle's contraction.

This filament's force is all or nothing, Baldwin says. It always applies the same amount at the same speed. Equivalent types of filaments are identical in Michael Jordan and Mother Theresa. But there the resemblance ends.

The filaments are bundled into muscle fibers about the size and shape of a thin hair a few millimeters to a few centimeters long. Jordan's fibers are perhaps twice as thick as Mother Theresa's, because physical conditioning and the male hormone testosterone have added more filaments for additional strength.

About 100 to 500 fibers are wrapped together like a package of spaghetti to form a "motor unit," the smallest muscle unit that can be controlled individually. When Jordan shoots a basketball, his brain calculates just how many and which motor units are required in various muscles and activates only them. If the calculation is correct, Jordan scores.

Your genes may not have endowed you with a professional athlete's muscle makeup, but you make similar calculations every time you lift a box or open a door.

The brain's orders reach the muscles because a nerve from each motor unit is plugged into the spinal cord like a telephone plugged into a wall socket. But unlike the telephone, if you unplug the muscle, it still works.

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