Months of spaceflight can leave astronauts feeling dizzy when they get back to terra firma. A new study published online in Circulation shows that up to 2 hours of daily resistance and endurance training during the mission, combined with IV fluid replacement upon return to Earth, completely eliminated dizziness and fainting during normal activity. The exercise regimen counters cardiovascular, bone, and muscular deconditioning.
The dizziness is related to low blood pressure after standing up from a sitting or lying down position. It results when blood rushes to the feet and away from the brain because of the movement. The phenomenon, known as orthostatic hypotension, has plagued the space program even before the Apollo 11 mission, which celebrates its 50th anniversary this week.
The finding is good news for astronauts, but the findings extend to full-time Earthlings as well. The same fitness program is helping patients with postural orthostatic tachycardia syndrome (POTS), which most often affects women aged 13-50 years, said senior author Benjamin Levine, MD. About 450,000 people suffer from the condition in the United States.
The program held up well against a difficult challenge. “What surprised me the most was how well the astronauts did after spending 6 months in space. I thought there would be frequent episodes of fainting when they returned to Earth, but they didn’t have any. It’s compelling evidence of the effectiveness of the countermeasures – the exercise regimen and fluid replenishment,” said Dr. Levine, who is professor of Exercise Sciences at UT Southwestern Medical Center, said in a press release.
The researchers studied 12 astronauts (8 men, 4 women) who were aboard the International Space Station for roughly 6 months. To monitor for orthostatic hypotension, the researchers used ambulatory beat-to-beat blood pressure monitoring during activities of daily living. The device was used for 24 hour periods before, during (day 15, 30, and 75, as well as 15 days before return to Earth), and immediately following space flight.
The research showed that 24-hour systolic blood pressure decreased, compared with preflight levels, during flight time (106 vs 120 mm Hg; P less than .01), but the values returned to normal after return to Earth (122 mm Hg). There was no change in diastolic BP during or after flight. Systolic and diastolic BP variability did not change before, during, and after flight.
The study was funded by NASA. Dr. Levine has no disclosures.
SOURCE: Qi Fu et al. Circulation. 2019 July 19. doi: 10.1161/CIRCULATIONAHA.119.041050.