When NASA astronauts Suni Williams and Butch Wilmore returned to Earth last year after an unexpectedly long nine-month stay on the International Space Station, they had to be carried from their capsule on stretchers. It was a vivid reminder that even the fittest humans can be left physically wrecked by extended time in space.
What happens to the body in microgravity is, in many ways, a sped-up version of aging. Bones lose up to 2 percent of their mass per month. Muscle strength can drop by 10 percent in weeks and 20 percent within three to six months. The spine destabilizes. Balance falters. According to New Scientist, this accelerated decline mirrors what many people on Earth experience after long hospital stays, injuries, or simply years of sedentary life.
Astronauts aboard the ISS now spend roughly two hours a day exercising — running on a special treadmill, cycling, and using resistance equipment designed for low gravity. Yet for many crew members, even that regimen isn't enough to fully counteract the damage. The shortfall has pushed researchers to look more carefully at which muscles matter most and how best to protect them.
One of the key insights from space medicine concerns the deep stabilizer muscles most people never think about. The multifidus, which runs along each side of the spinal column, and the transversus abdominis, which wraps around the trunk like a corset, are critical for keeping the lumbar spine steady. In microgravity, these muscles weaken rapidly because they no longer need to fight gravity's pull. The same deterioration happens on Earth when people sit for long stretches without engaging their core.
The takeaway for the rest of us is straightforward but often overlooked: conventional gym workouts that target visible muscles like the abdominals may not be enough. Exercises that activate the deep core — movements that challenge balance and require the spine to stabilize itself against gravity — may be more important for preventing back pain and maintaining mobility as we age. In other words, training like an astronaut doesn't require a spacecraft. It requires rethinking which muscles actually keep us upright.
