CNN  — 

The lack of gravity astronauts encounter during spaceflight makes returning to the force of Earth’s gravity a little disorienting. And when they return to Earth, they faint.

A new study published Friday in Circulation, the American Heart Association’s journal, has identified a way to avoid that.

Surgeons assigned to some of the first astronauts to go into space during NASA’s Mercury program noticed very few changes when they monitored heart rate, blood pressure and body temperature.

“But what changed was when they returned to Earth,” said Bill Carpentier, Apollo 11 flight surgeon. “The heart rate was increased post-flight and blood pressure was seen to be lower. And on the last Mercury flight, which was 34 hours, when Gordon Cooper got out of the spacecraft and stood up, his heart rate went really high, 170, 180. And his blood pressure dropped, he felt like he was going to faint. But once he started moving, things got better and he was able to walk across the deck.”

There was concern that this could become progressive with longer missions in the Apollo program that could last up to 14 days.

Orthostatic hypotension occurs when the blood rushes to the feet and away from the brain as someone stands up after sitting or lying down. This causes a temporary drop in blood pressure, which