Treatments used to help mend broken legs on horses may reduce bone-mass loss in astronauts and in osteoporosis patients, Colorado researchers say.

Veterinarians are using electrical stimulation on injured animals to work muscles and promote bone activity. That same principle is being applied to laboratory animals whose hind legs are suspended to simulate inactivity experienced in space, said Marvin Luttges, director of the University of Colorado's Bioserve Space Technologies, a NASA center for commercial development of space.Astronauts returning to earth and people whose illnesses keep them in bed both experience bone-mass loss, Luttges told science writers at the Council for the Advancement of Science Writing annual workshop.

It's the old use-it-or-lose it principle: Inactivity hastens bone-mass loss. For women who suffer from osteoporosis, a loss of bone mass that makes the joints less dense, not using the bones accelerates the loss of calcium and collagen that make up bones.

"This problem is rapidly simulated (for astronauts) in returning from a microgravity environment" such as space, said Luttges. Bones can restore their strength, but the loss is permanent.

When muscles move, an electrical current is created within the muscle that stimulates bones. No charge goes to the bones without muscular movement.

After four days in microgravity where bones and muscles don't work the same as on earth, 15-17 percent of bone mass deteriorates, Luttges said. The loss from lying in bed is about one-third the amount experienced in space.

"The very first thing you see in microgravity and bed rest is a loss of calcium," the researcher said. Even people who spend a couple of days in bed are a little wobbly when they get back on their feet. "It really is use it or lose it."

His experiments used 30 mice who were suspended by their tails, preventing them from using their hind legs, for 12 hours a day. A significant loss of bone mass occurs by the tail suspension similar to that experienced in microgravity. The animals quickly adapted to walking and working using only their front legs, Luttges said.

Straps containing oscillating magnetic currents relay electrical charges, similar to the zap experienced when walking across carpet and touching a television set, to the back legs for the other half of the day.

Animals that did not receive the stimulation experienced more bone-mass loss than the mice with the charged cages and straps. And that charging could be used in leg wraps for astronauts and bed coils for bedridden osteoporosis patients, said Luttges.

Osteoporosis is irreversible but the bone loss can be stopped, said Dr. Stanley Gould, a gynecologist and instructor at the University of Colorado Health Sciences Center in Denver, who studies the disease that affects women over the age of 45.

Women lose the hormone estrogen after menopause, and the average person loses 1 percent of calcium in the bones each year after the age of 35 to 40, Gould said.

Once the researchers establish that the magnetic charges work, the next step is reducing the amount of time the stimulation is required to offset bone-mass loss.

"We'd like to see if we could get away with six hours a day" of wearing the coils for astronauts, and administering the charge "through something like a mattress coil" for bed-ridden patients, Luttges said.