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TOPLINE
In astronauts who spent about 6 months in space and followed an in-flight exercise program, heart volumes and cardiac output initially decreased during microgravity but recovered toward preflight levels later in the spaceflight. After landing, heart volumes and function under simulated Martian gravity remained similar to those measured in flight 15 days before landing.
METHODOLOGY
- Researchers conducted a prospective, within‑subject observational study to track cardiac changes during long‑duration spaceflight and after exposure to simulated Martian gravity.
- They included 13 astronauts (mean age, 49 years; nine men) who flew for a median of 164 days.
- Echocardiographic data were acquired before flight during supine rest and upright tilt at specific gravitational loads (including simulated Martian gravity), during spaceflight at multiple timepoints, upon landing on Earth, and after landing during exposure to simulated Martian gravity.
- All astronauts followed a daily countermeasure program during spaceflight, combining endurance work (30-45 minutes) with resistance training (60-75 minutes), for a total of up to 2 hours per day.
TAKEAWAY
- At 14 days in microgravity, stroke volume decreased from 78 mL to 54.2 mL, and cardiac output decreased from 4.34 to 3.16 L/min compared with preflight supine values (P < .001 for both).
- Compared with preflight upright values, most in-flight measures were broadly similar at about 14 days in flight, but longitudinal strain increased from -14.5% to -17.03%, whereas circumferential strain decreased from -25.97% to -22.13% (P < .05 for both).
- Over the duration of spaceflight, left ventricular end-diastolic volume and stroke volume showed an increasing trend toward preflight supine values. No significant changes were observed in left ventricular mass or wall thickness and measures of strain.
- After landing, supine cardiac output and longitudinal strain both rose compared with in-flight measurements 15 days before landing (P < .05 for both). Chamber volumes and function under simulated Mars gravity after landing did not differ significantly from in-flight measurements taken 15 days before landing.
IN PRACTICE
"[O]ur practical findings demonstrate the importance of current countermeasure exercises in preserving cardiac structure and function throughout prolonged spaceflight, which in this study was ≈ 6 months, consistent with the estimated duration of interplanetary spaceflight travel to Mars," the researchers wrote.
SOURCE
The study was led by Vinesh Appadurai of Northwestern University in Chicago. It was published online on September 15 in Circulation.
LIMITATIONS
The study had a small sample size. Participants were healthy astronauts who followed relevant exercise routines, which may have limited the applicability of the results to other groups.
DISCLOSURES
The study received funding from the National Space Biomedical Research Institute and directly from the National Aeronautics and Space Administration. One author reported receiving support from the Irene D. Pritzker Foundation and the Sandra Helton Foundation. Another author reported receiving support from the National Heart Foundation of Australia.
This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
