A workout that's out of this world
Updated 1:42 am, Wednesday, August 7, 2013
HOUSTON — How do you lift weights in microgravity?
Exercising on a satellite floating 200 miles above the surface of the planet presents some unique challenges. But working out is so essential to counter the adverse effects of weightlessness on the body that astronauts aboard the International Space Station devote about 2 to 21/2 hours to exercise every day.
“I'm a little less disciplined here on Earth,” said NASA astronaut Doug Wheelock, whose first spacewalk was in 2007. “Up there, I just stayed to my schedule because I was so distressed about being able to get back to the Earth and not being able to walk. I lost like 12 pounds and like 10 percent body fat. Of course I let that go when I got back to Earth.”
Last month, NASA invited reporters and social media experts to a daylong event at Johnson Space Center to learn how astronauts stay fit during missions. Astronaut Mike Hopkins, who will be heading to the space station in September, has launched a new social media fitness program, Train Like Mike. Viewers can follow his in-space workouts at twitter.com/TrainAstronaut and Facebook.com/Train Astronaut.
In microgravity, astronauts don't exert as much force on their muscles, which affects their fitness levels. Without exercising, astronauts can lose an average of 1 to 2 percent of bone density per month in space; on Earth, an elderly person loses about 1 to 2 percent per year. Astronauts could lose up to 15 percent of their muscle volume without strength training. Cardiovascular function also diminishes.
Crew members in orbit use a treadmill, stationary bike and a resistance machine for strength training. Working out in microgravity takes some adjustment (not to mention they can't shower or do laundry afterward).
“It's not intuitive. You just don't have the gravity cues,” said astronaut Tracy Caldwell Dyson, who lived aboard the International Space Station as a flight engineer in 2010. “You have to overcome some instincts.”
The most obvious problem with exercising in space? How to keep from floating away from the equipment. On the treadmill, astronauts wear a harness with bungee cords that tether them to the machine.
Running in microgravity felt “really, really weird” for the first few weeks, Wheelock said. “You feel really clumsy and you're kind of running quite flat-footed.”
When crew members pedal the bike, which has no seat, they clip their shoes to the pedals to stay connected to the machine.
“It's really hard to ride a bike in weightlessness because you have no leverage,” said Bob Tweedy, NASA countermeasures system instructor. “Down here, you can stand up and mash down on the pedals with your body weight. You can't do that (in space). Plus you're (floating) around.”
Probably the most high-tech piece of equipment is the Advanced Resistive Exercise Device, or ARED, which resembles a weight machine without the weights. The contraption uses piston-driven vacuum cylinders to provide resistance. The astronauts use dials to adjust resistance, up to 600 pounds.
Astronauts can lift a lot more weight in orbit than they can on Earth, because they aren't lifting their own body weight.
The squat and the deadlift, very high-load exercises, are two of the main exercises they do, Tweedy said, because they work some of the most common areas of bone loss, including the hips.
There's one way in which exercise is easier in space: The astronauts recover a lot faster, Tweedy said, because they're not carrying the load of their own body weight post-workout.
“Crew members have told me they felt fine the next day,” Tweedy said. “Not as sore, not as fatigued, more rested.”
In the past, astronauts underwent fitness testing before and after flight. But in the last couple of years, scientists have designed ways for astronauts to perform fitness assessments on the space station. Ultrasounds can measure muscle mass, while VO2 max testing measures cardiovascular function.
Now NASA researchers are experimenting to refine the astronauts' exercise protocol, using regular testing to measure fitness and adjust the workout accordingly. The research study, called SPRINT, is evaluating an exercise program that includes high-intensity interval training alternating with resistance training.
“Our dream goal is to come up with an hour or two a day of exercise you could do that would completely protect your cardiovascular, your muscle and your bone systems against 23 hours a day of lying around,” said Lori Ploutz-Snyder, an exercise physiologist at NASA. “So we have a big task ahead of us.”
The goal is to determine how astronauts can maintain their fitness levels on missions longer than six months, the typical length of missions now. In 2015, two astronauts will undertake a 12-month mission. Missions to Mars are expected to last two to three years.
The findings can benefit those of us on Earth, too. Ploutz-Snyder said researchers could figure out how to design exercise to help people on bed rest to maintain their fitness levels.