Space Fitness Research May Aid Invalids : Health: Astronauts lose bone and muscle mass while in orbit. Efforts to halt that could provide new ways for Earth-bound people to exercise.

Astronauts and invalids have something in common.

Being off their feet--either in space or in bed--leaves muscles and bones weakened. So studies aimed at keeping astronauts strong when they don’t even have the pull of gravity to fight may pay off for people on Earth, researchers say.

“What we are learning from bed rest and from actual space flight is what sorts of procedures are best for recovery of function after disuse,” said Frank Sulzman, chief of the National Aeronautics and Space Administration’s research branch. He spoke in a teleconference after an Indianapolis meeting hosted by the American College of Sports Medicine in conjunction with NASA.

NASA’s goal is to keep space travelers as strong at the end of a long trip as they were when they started. It’s vital for astronauts on a space station or a trip to Mars, but no one yet knows how to do it.

The Russians, who leave cosmonauts on the space station Mir for months at a time, have an extensive in-orbit exercise program, Sulzman said. The cosmonauts work out two hours a day, three times a week in the early going, and double the number of hours toward the end, he said. Cosmonauts use exercise bikes and rowing machines to fortify their endurance; they also pull against elastic cords to simulate weight training in an attempt to preserve strength, he said.

Even this, however, doesn’t prevent some loss, Sulzman said. Cosmonauts lose about 1% of their bone density per month in such areas as the hip and lower spine, he said.

Astronauts, whose time in orbit is far shorter than the cosmonauts’, take aerobic equipment on space shuttle trips but are only experimenting with resistance equipment. Elastic cords were tried in the 1960s, but they were not good enough, Sulzman said. So NASA is looking at whole-body resistance equipment that could be used on an international space station, the first element of which is to be launched in 1998, he said.

Prototypes have been tested by people who lie in a horizontal position, as if they were in bed, Sulzman said. One version is to be tested on an upcoming shuttle flight, he said.

The space program also wants to cram as much exercise into the least time, said conference co-chairman Timothy P. White of the University of California, Berkeley. “The most valuable commodity is an astronaut’s time,” and time spent exercising can’t be used for other parts of the mission, he said.

The other co-chairman, Kenneth Baldwin of the University of California, Irvine, has been experimenting on lab animals, using computers to add electrical stimulation to muscle. The goal is “maximal or near-maximal force output,” Baldwin said.

This could pay off for Earth-bound exercisers. Stimulating more muscle cells to contract could result in doing as much work in two to five exercise repetitions as is done normally in 10-15 repetitions, Baldwin said.

This would take electrical stimulation beyond its current use in some therapies, such as strengthening knees after surgery, Baldwin said.

Some elite athletes hook themselves up to electrodes, hoping for additional training while they sleep, but there’s no good evidence this works, White said.

And there are risks to playing with electricity, Baldwin said. “In animals, if one stimulates just for the sake of zapping, you induce muscle atrophy,” he said.

Also, electrical stimulation devices may not be all they are touted to be, Baldwin said. Quacks have often come up with electrical muscle-builders that just don’t work, he said.