This is What Microgravity Does to Your Body

U.S. astronauts Barry “Butch” Wilmore and Sunita “Suni” Williams splashed down to Earth on Tuesday after more than nine months in space.

But now, they have a new mission: recovery.

Why it matters: Muscle atrophy, bone density loss and even vision changes are expected side effects of long-duration space missions. And while some of the impacts of a layover hundreds of miles above Earth are quickly reversible, others can persist.

Wilmore and Williams splashed down Tuesday evening after undocking from the International Space Station early that morning.

Zoom in: One prominent effect of extended time in microgravity is muscle atrophy or weakening. The longer a space mission is, the more severe such atrophy would be, said Shenhav Shemer, a professor of biology at the Technion — Israel Institute of Technology who researches muscle loss.

Williams and Wilmore may experience this atrophy differently: Women — who naturally have lower baseline muscle mass and testosterone levels in addition to hormonal and metabolic changes they experience in space — are more susceptible to atrophy and bone loss, Shemer said.

Resistive exercise can help combat that loss, with crew members averaging two hours of exercise per day, according to NASA.

But even with routine training, Shemer said, astronauts will still experience atrophy in space.

As bones lose their density, the body’s mineral content increases elsewhere, which can lead to issues like increased urinary calcium and kidney stones, according to Baylor College of Medicine.

NASA has found that without Earth’s gravity, weight-bearing bones lose on average between 1% and 1.5% of bone mineral density per month.

Keep reading at axios.com.