How does gravity maintain the heart?

How does gravity maintain the heart?

A new study published Monday by the Journal of Circulation of the American Heart Association reported that astronaut Scott Kelly, who spent a year in space, had a shrinking heart despite working 6 days a week during his stay.

In addition, researchers observed the same change in the heart of French swimmer Benoit Lecomte, after he completed a 159-day swim across the Pacific Ocean in 2018.

The results also indicated that long-term weightlessness changes the heart's structure, causing contraction and atrophy, and that low-intensity exercise is not enough to prevent this from happening.

Gravity keeps the heart

According to the study published by CNN, it is gravity on the ground that helps the heart maintain its size and function, as it keeps blood pumping through the veins, even simple things such as standing and walking help draw blood to the legs.

Whereas, the response of the heart muscle decreases when the component of gravity is replaced by weightlessness.

Kelly lived in zero gravity aboard the International Space Station from March 27, 2015 to March 2016, XNUMX, and trained on a stationary bike and treadmill as well as incorporating resistance activities into his routine six days a week for two hours each day.

In contrast, from June 5 to November 11, 2018, Lecomte swam 1753 miles, averaging about six hours a day. This continuous activity may seem intense, but every day of swimming was considered a low intensity activity.

Although the French swimmer was on land, he spent hours of his day in the water, offsetting the effects of gravity. Long-distance swimmers use the prone technique, which is the horizontal face-up position for swimming.

Exercise keeps the heart fit

Also, the researchers expected that the activities carried out by both men would preserve their hearts from any contraction or weakness. Both Kelly and Lecomte experienced a loss of mass and an initial decrease in diameter in the left ventricles of the heart during their experiment.

Both long spaceflights and long dives into water led to a very specific adaptation of the heart, said lead study author Dr. Benjamin Levine, professor of internal medicine and cardiology at the University of Texas Southwestern Medical Center.

While the authors note that they only studied two men who did unusual things, more study is needed to understand how the human body reacts in extreme situations.

No negative effect

In this case, the researchers saw that the heart adapted, but the contraction did not cause any present or long-term adverse effects.

The heart gets smaller, it shrinks and atrophies, but it doesn't get weaker — it's fine," said Levine, who is also director of the Institute for Exercise and Environmental Medicine.

He added that since the body is accustomed to pumping blood upwards against gravity in a vertical position, when this gravity stimulus is removed, especially in someone who is already active and fit, the heart adjusts to this new load. He pointed to the flexibility and adaptability of the heart muscle, with nearly three-quarters of the muscle responding to physical activity.

He also explained that the heart muscle adapts to space flights, exercise, and high altitudes, as it is a remarkably adaptive organ that responds to the demands placed upon it.

He concluded by explaining that the size of the heart muscle increases as the load on it increases, and the same thing happens in the opposite direction.

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