Astronauts in space live in a whole different world. And one of the biggest differences, besides probably the lack of oxygen, is the lack of gravity. Thanks to this we have some pretty cool images of suspended water bubbles and astronauts walking on the ceilings of space shuttles. But, the microgravity present in space also poses some challenges - namely, the impact it has on an astronaut's body. We don’t really notice, because we’ve habituated, but on planet earth, our body is constantly working out.
Gravity pulls us down and our muscles and bones must resist that tension to keep us upright and moving - sorta like mini workouts. But, in space, this tension virtually disappears. Which is really bad, because muscles can atrophy and bones can lose density. Just like muscles, bones are living tissues that need exercise to stay healthy. This is why on average NASA astronauts spend 2.5hrs per day working out in space.
But it looks a bit different from what we see here on earth. Pushups, jumping jacks, running, or anything really that doesn’t involve equipment, just doesn’t work for them. They use special exercise machines. The three main ones at the International Space Station are the Colbert, Cevis, and Ared.
The Colbert is actually short for Combined Operational Load Bearing External Resistance Treadmill. It is basically a treadmill but astronauts must be harnessed in place. The Cevis or Cycle Ergometer with Vibration Isolations and Stabilization System is like a bicycle, but because without gravity you can’t sit down, astronauts stand and strap their feet to pedals. Lastly, the ARED or Advanced Resistive Exercise Device resembles a weight training machine which can be used for things like deadlifts, calf raises and squats through a piston-driven vacuum cylinder and flywheel system.
All of these modifications are necessary because objects lack any weight and regular lifting would be way too easy. So does this mean all regular exercise is easier in space? Not, exactly. Zero gravity does mean that the lack of resistance might make it easier for astronauts to lift things that would weigh hundreds of pounds on earth.
But here’s the thing. While in space your body fluids, sort of just floating all around your body. Without gravity, there is nothing to pull blood down below the heart to your legs and toes. The vast majority of blood just hangs out around the heart and head.
So astronauts have less plasma and red blood cells to carry oxygen to their muscles. This is a problem for things like running or burpees because the lack of oxygen can cause dizziness, and therefore impede performance. Still, despite the hours spent working out every day with specialized equipment, astronauts bodies take a toll. On average, NASA reports that they suffer decreases of 11 to 17% of their muscular strength and about 10% of their muscle endurance.
Their bone density also tends to decrease about 2 to 7%. And according to an International Space Station scientist, about 80% report feeling lightheaded shortly after returning to earth. This is largely why scientists have multiple studies underway to figure out how to improve exercise in space and diminish the negative health effects of spaceflight.
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