“Exercise is pretty powerful under these conditions,” said Lori L. Ploutz-Snyder, dean of the University of Michigan’s School of Kinesiology, who was formerly a senior exercise scientist at the Johnson Space Center in Washington. NASA in Houston and co-author of the new research.
But there is a catch. To faithfully recreate low-gravity workouts, we’d need to run straight up against a wall, like the cartoon Roadrunner, and train in bed. With a few tweaks, however, astronauts’ daily exercise routines can work on Earth and help us develop our own unique physical fitness.
Why Astronauts Need Exercise
Space travel is hot right now, as NASA’s new Orion spacecraft circles the moon, the International Space Station continues its long-term Earth orbit and private rocket companies offer tourist getaways at exorbitant prices to the stars.
Unfortunately, our bodies are not well adapted to space. In microgravity, muscles and bones do not support weight and quickly shrivel up, and cardiovascular fitness plummets.
“Without regular exercise, we would lose significant muscle mass and bone density,” said Jessica Meir, a scientist and astronaut who served as a flight engineer on the International Space Station.
Hoping to stem such declines, NASA added exercise equipment to the space station in the 1990s, and astronauts began to train slowly and painstakingly for several hours a day, doing their pace to avoid injury and fatigue. But their muscles and physical condition declined further.
So, in the early 2010s, Ploutz-Snyder and his fellow NASA scientists started thinking about intensity. At that time, exercise science showed that short bursts of intense, all-around exercise build strength and endurance.
Could this kind of short, intense exercise be effective and safe in space, the scientists wondered? To find out, they asked 34 Earthlings to go to bed and stay there, non-stop, for 70 days.
Trying out HIIT workouts in bed
The head-down tilting bed is the best, and most mind-bending, science simulation of space travel. In head-down bed-rest studies, people lie, day and night, in beds that are angled six degrees so that their head is pointing down and their feet are angled up. Fluids go to their heads, as if in weightlessness, and muscles and endurance atrophy.
At the start of head-down bed rest, the once-healthy volunteers’ physiques quickly turned to goo – their muscles softening and shrinking, like what you would have seen if they had spent months in space.
But Ploutz-Snyder and his colleagues hoped the right exercise program could keep bedridden volunteers fit and, if so, could be used in space. So their engineers mounted treadmills on the side to replicate zero-gravity running, brought in bikes and weight machines that can be used in bed, and had some of their volunteers train almost every day, on your back, for a few minutes to an hour.
Others remained completely sedentary as a control. (All volunteers, ages 24 to 55, had undergone medical and psychological screenings before the study began and were paid for their participation. None dropped out.)
The six-times-a-week exercise routine centered on what the researchers called “undulating periodization,” meaning some days they did high-intensity intervals of varying duration and others they lifted weights and were doing aerobic training.
In more detail, the volunteers sprinted on the lateral treadmill three times a week through high-intensity intervals (lying on their sides, in the air, hitched to the ceiling). Once a week, the intervals consisted of eight full 30-second sprints; another day of six two-minute intervals; and on day three, four four-minute intervals, all with brief rests between sprints.
Every other day, volunteers rode stationary bikes and lay in bed at a brisk pace for about 30 minutes.
Later that day, they got up in bed, grunt through squats, leg presses, heel raises and leg curls, using weights heavy enough that they could barely complete eight to 12 repetitions.
The program has been calibrated to emphasize and strengthen multiple aspects of the cardiovascular system and large lower body muscles in as little time as possible, Ploutz-Snyder said.
The results indicate that the recumbent workouts were successful. Practitioners retained most of their muscles and nearly all of their stamina, and suffered almost no injuries except for ear infections caused by sweat leaking into their ear canals while they practiced in bed.
But day after day, throughout the 70 days of the study, inactive controls became less fit and more punished. The scientists enrolled them in a separate 11-day exercise and rehabilitation program after the study ended.
“The most compelling part of this story, to me, is that an average of one hour of exercise per day protected people against 23 hours per day of lying in bed,” Ploutz-Snyder said. “No medicine can do that.”
Data in hand, she and her colleagues then persuaded NASA to try the program in space. At the time, in the mid-2010s, astronauts were training up to 2.5 hours a day, almost all at a moderate pace. Now some of them have started the new routine, running or cycling for a few minutes of short, precise intervals three times a week and lifting hard but quickly on other days, while jogging or space biking for about 30 minutes. Their weekly exercise time more than halved. (Since the study ended, astronauts on the International Space Station have continued to mix intense and moderate exercise, albeit in different combinations.)
Meir, who was in space for 205 days during the International Space Station missions in 2019 and 2020, praises the effects of his training there. “Exercising on the International Space Station is an extremely important part of our routine,” she said.
Lessons for exercising on Earth
The astronauts in the study returned to Earth with much, but not all, of their stamina and strength intact.
There’s a lesson in their losses and their gains for the rest of us, Ploutz-Snyder said. Long hours spent sitting are no different, physiologically, from floating in space. Our muscles, heart and lungs are inactive when we sit, and if this inactivity continues, they lose their function.
So get up and get moving, Ploutz-Snyder said. Any activity will be better than none. But for an effective and efficient exercise routine, she said, try scientifically tested space training, but not from bed. Use a bicycle or treadmill (located on the floor, not on the wall) or walk at high speed up a hill. If that sounds daunting, chain interval sessions over a few weeks.
The full program can easily fit into most of our schedules, she said, and has insinuating appeal.
“It’s effective,” she said, and effective, and as an added endorsement, “many astronauts have continued the program after their missions have ended.”
Do you have a fitness question? E-mail YourMove@washpost.com and we may answer your question in a future column.
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