Researchers have found a way that can help astronauts spend a long time in space returning to Earth with a more stable footing.
"One of the biggest problems since the start of the manned space program was that astronauts fainted when they descended to Earth. The longer the time in space is free of gravity, the greater the risk arises," said Benjamin Levine, a professor at the University of Texas Southwest Medical Center ( UT) in the US.
"This problem has long disrupted the space program, but this condition is something ordinary people often experience too," said Levine, director of the Institute for Exercise and Environment Medicine at Texas Health Presbyterian Hospital. Orthostatic hypotension is a technical term for a temporary decrease in blood pressure when a person is standing after sitting or lying down because blood flows rapidly to the feet, away from the brain.
Dizziness or fainting due to changes in blood flow can occur after a long bed rest, among people with certain health problems or, in the case of astronauts, in a low gravity environment.
The study, published in the journal Circulation, included 12 astronauts (eight men and four women aged 43-56) who spent about six months in space.
All do endurance exercises and individual resistance training for up to two hours every day during space flight to prevent cardiovascular, bone and muscle deconditions. They also received saline infusions on landing.
The blood pressure of astronauts is recorded with each heartbeat every 24 hours before, during and after their time in space.
The researchers found that there was a minimal impact on their blood pressure during all phases of measurement and no astronauts in the study experienced dizziness or fainting during routine activities 24 hours after landing.
This is the first study to show that astronauts do not experience dizziness or fainting during routine activities after landing, as long as they participate in certain types of exercise while on flight and receive IV fluids when they return to earth, Levine said.
"What surprised me most was how well astronauts did after spending six months in space. I thought it would often faint when they returned to Earth, but they did not have it. This is strong evidence of the effectiveness of astronauts." "exercise and fluid filling regimens," he said.
The researchers noted that the sample size was small. Also, they cannot clearly distinguish whether special blood pressure readings on flights occur when astronauts wake up or fall asleep, so that data is combined and examined over a 24-hour period.
Because all astronauts participated in the exercise regimen and received an infusion of saline fluid at landing, the researchers did not know that blood pressure stabilization would occur without those steps.