We just can't seem to escape exercise no matter how far we go.
Even if we travel to Mars, where U.S. scientists are planning a joint trip with the Soviets. Or to the moon, where scientists dream of orbiting space platforms and mining communities.
Yet, if the Lunar-Mars initiative--what these dreams are officially called--becomes reality, so will the problems of microgravity, a condition that has one-sixth the gravity of Earth. The last time a U.S. astronaut spent prolonged time in space travel, in the Skylab series in the '70s, he returned a little bit shorter because of bone loss in the heel bone. A fair amount of cardiovascular and muscle deterioration also occurred.
Scientists learned from Skylab, which orbited the earth for 84 days, and also from a one-year Soviet space mission, that astronauts have physical problems adjusting to microgravity and then readjusting to earth.
"It took about two or three weeks for our astronauts to physically come back to normal after Skylab, and reports are that it took a month or two for the Russians . . . and we don't know if the Russians regained their bone loss or not," said Dr. Bernard Harris of the Johnson Space Center in Houston.
Because bone is a living tissue, it will respond to the stress that is placed on it. In space there is little stress, so the bone actually decreases in size to make the skeleton lighter.
The problem, according to some researchers, is that after two or three years in space a human may not regain the same level of bone and bone density, which in turn could result in a loss of strength.
The prescription to this dilemma--scientists believe--is exercise.
That's why Space Station Freedom, scheduled to launch in 1996, will include an exercise facility in the spaceship.
The facility will include a treadmill, a bike rower used for cycling and rowing, and a weightlfiting machine called a tork. The tork has an electric motor to provide resistance, and different attachments to perform bicep curls, tricep extensions and leg and military presses.
Exercise in space results in other problems. Scientists are trying to make the exercise period short enough so that it does not impact the space mission.
"We have ongoing studies in simulated microgravity to see if we can cram an entire daily activity that a person would do, including the exercise, into a two-hour period, which would include the treadmill and bike rower, etc," Harris said.
To determine force, Harris doubles a person's body weight and then multiplies that figure by the number of steps the person takes during a day. A program is then prescribed on the treadmill, adjusting speed, grade and steps to equal the required amount of force expenditure.
"We put the subject in bed and get him up for any period of time you are going to cram this into," Harris said. "Actually, some health spas are taking this concept and coming up with 30 minute workouts. The body experiences the total load and force that you would have if you worked out for two hours at a lower intensity."
Exercise in space will have a different twist and produce different results. In running, for example, elastic cords, which may be the business of the future, will be used to keep a runner on the ground. Because there is little gravity, there will be no force generated from the weight of the runner's foot hitting the ground. The major force expended will be from the resistance of the runner moving against the elastic cords.
In weightlifting, force must be produced because nothing weighs anything in space.
"So if you lift five pounds down here with your biceps, you are lifting against gravity and are also holding your arm up against gravity," Harris said.
"If you take the same body and put it into microgravity, it's not lifting anything but pulling against the weight itself. So the characteristics of weightlifting will be different."
The alternative to trying to exercise in microgravity is to produce artificial gravity in space. At the NASA Ames Research Center at Moffett Field, Calif., researchers are studying the creation of artificial gravity through centrifugation--rotating the spacecraft, which is connecting to a rotating device, by a long chain. One of the Gemini missions experimented with the concept and it was deemed it feasible.
Dr. Rob Whalen, a research scientist at Ames, says scientists are also studying the relationship between exercising at a higher gravity level, even higher than the 1G on earth, for a shorter period of time. They also are studying the use of simulating the earth's gravity for intermittent exposure to astronauts in space travel.
"Right now in our technology we don't have the means to produce artificial gravity effectively, but we know that is probably the answer to space travel and life in space," Harris said.
In that case, exercise, as well as sports, could be performed in space in much the same as on earth. But it may not be as much fun.
"I was asked a couple of years ago if we could play football on the moon, " Harris said. "I said yes, but since the moon's gravity is one sixth that of the earth's, we would have to have a field about six times as large, because you could throw the ball farther. Each step you take would be a longer one. There are things unique to the moon that would make sports very interesting."
Harris also thinks the environment of space will create its own sports, whether a variance of sports as we know them on or new sports.
"Jumping may be a possibility," he said, laughing.