After collecting cardiovascular data from an astronaut and a long-distance swimmer after their respective activities, scientists have concluded that low-intensity exercise is not sufficient to prevent the heart from weakening under low-gravity conditions. Researchers from UT Southwestern Medical Center created this project in order to assess the physiological changes that space travelers experience when they leave earth’s gravitational field and become weightless, with the ultimate goal of optimizing the health of astronauts and increasing the feasibility of space travel. On the surface of earth, gravity plays a direct role in strengthening the heart by forcing it to work hard to counteract the gravitational force that drives blood towards the lower body. When gravity is removed and blood can be circulated through the body with less effort, the heart can shrink and weaken, also known as atrophy of the heart. One way that weightlessness is simulated on Earth is via submersion in water, which can mimic the effects of being in space. While aboard the International Space Station (ISS) for one year, Scott Kelly exercised six days a week for a couple hours at a time, while Benoit Lecomte swam for six hours a day for five months while completing his journey across the Pacific Ocean. Despite the consistent exercise, both participants experience a decrease in left ventricle mass and left ventricle diastolic diameter, meaning that their hearts both shrunk and did not fill with as much blood on each heartbeat. Despite the failure of low-intensity exercise to prevent the deterioration of cardiovascular strength for people experiencing weightlessness, the effects of high-intensity exercise at less frequent intervals remain to be tested and offer a strategy for astronauts to remain healthy on missions as mankind prepares for the age of space exploration. To learn more, click here.