New Study Shows Space Travel Can Shrink The Human Heart

Mar 31, 2021

It turns that out that spending a year in space can shrink your heart. A new study published this week examines the effects of weightlessness on the human cardiovascular system. KNAU’s Ryan Heinsius reports.

Astronaut Scott Kelly takes a photo of himself inside the International Space Station in 2015.
Credit Scott Kelly/NASA via AP

Astronaut Scott Kelly, twin brother of Arizona Democratic Senator Mark Kelly, spent nearly a year on the International Space Station between 2015 and 2016. Despite a rigorous six-day-a-week workout routine that included cycling, treadmill and resistive exercise, researchers say the largest chamber of his heart, the left ventricle, shrank by more than a quarter during his 340 days in zero gravity.

According to the study published in the journal Circulation, a lack of gravity and weight-bearing activities can result in the type of cardiac atrophy experienced by Scott Kelly.

But it’s not just spaceflight that can cause shrinkage. Researchers observed a similar effect on the heart of elite French endurance swimmer Benoît Lecomte. He spent 159 days attempting to swim across the Pacific Ocean in 2018, logging nearly six hours a day buoyant in the water.

As CNN reports, no short or long-term negative impacts were observed in Lecomte or Kelly as a result of losing mass in their hearts.