The Space Cycle: New Way to Exercise in Orbit

"It's like hanging a little set of barbells on every molecule in your body."
-- Vincent Caiozzo, project leader on the Space Cycle

For most space travelers, the first effect of weightlessness they feel is nausea. But over the next few days and weeks, the lack of gravity takes its toll on the rest of the body, leading to muscle and bone mass depletion and troubles regulating blood pressure.

To counter these losses, astronauts on the International Space Station spend hours exercising everyday. But even this can't compare to a workout with gravity. When they return to Earth after a long mission, astronauts spend weeks rebuilding muscle and repair bone.

Now, researchers at UC Irvine and the National Space Biomedical Research Institute (NSBRI) have developed a two-person, centrifuge-like, one-stop workout machine that makes its own gravity.

They call it the Space Cycle.

How it works

Imagine a two-person, hanging merry-go-round. A spinning wheel sits on top of a thick steel pole. On one side of the wheel hangs a recumbent bicycle. Opposite the bike is a cage-like platform. One person sits on the bicycle while the other stands on the platform.

As the bicycle rider pedals, the merry-go-round begins to spin, causing both the bicycle and the platform to spin around the pole. As the merry-go-round spins faster and faster, both the bicycle rider and the person on the platform begin to feel the effects of artificial gravity caused by the momentum of the device.

The person on the platform can now perform squat exercises at gravity equal or greater – the researchers have produced artificial gravity seven times that of Earth – to what they would experience on Earth.

"If you go to a gym and do squat resistance training, you have this concentration of weight in the form of a barbell across your shoulders, which is quite uncomfortable," project leader Vincent Caiozzo of UC Irvine and NSBRI told "With hypergravity, the distribution is equal throughout the body. It's like hanging a little set of barbells on every molecule in your body."

Squats – an exercise where a person stands upright with a load on their shoulders, lowers themselves to a crouch, and stands back up - strengthen the calf, thigh, and back muscles, which are also the muscles where up to 25 percent loss occurs. But Caiozzo doesn't want to stop there.

"The way I envision the platform now is to use it as a hypergravity exercise gym," Caiozzo said. "Imagine you have a bar above your head, you could do pull ups. Or, we could put a treadmill on the platform and it would be like running on Earth."

And the biker gets a good workout too - while the person on the platform is doing the heavy lifting, the biker is in charge of keeping the whole thing spinning and experiences a gravity increase as well. If the biker needs to work out their upper body, they can switch to a hand pedal attachment for the 10-speed bike.

Not just a muscle builder

Muscle loss may be the most glaring effect of time spent in microgravity, but bone loss is just as big a problem, especially since once bone is lost, it's very difficult to regain.

"Bone mass is lost at different rates in different parts of the skeleton. In the hip, the rate is between 1 percent and 3 percent per month," said Joyce Keyak of UC Irvine. "Over a 6month mission, the loss of bone mass in the hip averages about 15 percent. Loss of bone in the hip is particularly important because the hip supports the body when we walk."

For now, scientists don't know whether this process can be reversed once the astronaut returns to Earth. Ongoing studies show some recovery of bone mass and strength, but the bone is never as good as it was pre-flight.

However, Keyak believes that the Space Cycle could act as a preventative measure.

"The Space Cycle may help astronauts retain their bone mass and bone strength by creating forces on the body that resemble those due to gravity," Keyak said. "Not only is force applied to the skeleton, but fluids tend to be shifted toward the feet, just like on Earth. By applying these conditions for a period of time, we hope that the bone will respond as if it were in a gravitational field."

Spending a little time exercising in artificial gravity may also help astronauts regulate their blood pressure better. After being in microgravity for an extended period, coming back to Earth's gravity causes all the blood in your body to pool in your legs and away from your brain – like when you stand up first thing in the morning and see spots in front of your eyes.

However, when you stand up from bed, the muscles in your legs help pump blood back up towards your brain, but you don't have that luxury when you leg muscles have lost their strength after weeks in microgravity and it takes a few days to get your blood pressure right.

"While they're up there, they're also losing aerobic capacity and conditioning," Hicks said. "Through the work and the artificial gravity effects, this could be a one stop exercise center for these guys."

Time saver

Astronauts on long space missions currently spend about two hours of their extremely busy day exercising to combat the effects of microgravity. But by using the Space Cycle and the artificial gravity it produces, astronauts may be able to make better use of their time.

"Anything that would help reduce the time of exercise would be beneficial," Caiozzo said. "If we can narrow that time down to half an hour, that would be great."

Caiozzo and his team are still testing the Space Cycle to determine how much good it might do in space. One problem with evaluating its effects, though, is that prolonged exposure to microgravity is still not fully understood.

"It could be that 24 hours in a microgravity environment is such a stimulus that you can't overcome it," Caiozzo said. "Even in you're on the bike for 4 hours a day, it might not be enough to overcome the other 20 hours in microgravity."

The next step in this research will to be to test the effects of exercise on bed-ridden subjects, who show muscle and bone atrophy similar to people returning from space.

Scientists are hopeful that the Space Cycle will prove to be effective at preventing bone and muscle loss, and say it may help astronauts' minds as much as their bodies. 

"One of the common things that individuals want to have is a place where they can do exercise," said Caiozzo. "There's a behavioral component to it – many of us feel better when we exercise and worse when we don't."

Currently, the Space Cycle's diameter is about 12 feet and the whole thing is made of steel, so it weighs a lot. Caiozzo says that its weight could be brought down to 50 to 100 pounds total by using carbon composite materials, and its diameter could be reduced by about a foot.

"That puts it in the dimensions for the International Space Station, and we've been told to think of a 12 to 13 foot diameter for crew exploration vehicles," Caiozzo said.