Sustained low-intensity exercise does not completely counteract the effects of weightlessness on the heart muscle, which will atrophy over time in a gravity-free environment. Short bursts of repeated high-intensity activity during shorter space missions may be more successful in keeping the heart healthy.
Each time a person sits or stands, gravity draws blood into the legs. The work the heart does to keep blood flowing as it counters Earth’s gravity helps it maintain its size and function. Removing gravitational effects causes the heart to shrink.
Researchers examined data from retired astronaut Scott Kelly’s stint aboard the International Space Station from 2015 to 2016 and elite endurance swimmer Benoit Lecomte’s swim across the Pacific Ocean in 2018.
In this new study, researchers evaluated the effects of long-term weightlessness on the structure of the heart and to help understand whether extensive periods of low-intensity exercise can prevent the effects of weightlessness.
«The heart is remarkably plastic and especially responsive to gravity or its absence. Both the impact of gravity as well as the adaptive response to exercise play a role, and we were surprised that even extremely long periods of low-intensity exercise did not keep the heart muscle from shrinking,» said Benjamin D. Levine, M.D., the study’s senior author and a professor of internal medicine at UT Southwestern Medical Center and director of Texas Health Presbyterian’s Institute for Exercise and Environmental Medicine, both in Dallas.
The research team examined the health data of Kelly’s year in space aboard the International Space Station and Lecomte’s swim across the Pacific Ocean to investigate the impact of long-term weightlessness on the heart. Water immersion is an excellent model for weightlessness since water offsets gravity’s effects, especially in a prone swimmer, a specific swimming technique used by long-distance endurance swimmers.
Story Source: Materials provided by American Heart Association. Note: Content may be edited for style and length.