A recently released study claims when astronauts spend a long periods of time in space, their hearts start to become spherical, which could mean trouble for future missions.

The findings were carried out by NASA and based on analysis of 12 astronauts who worked at the International Space Station.

The study was presented at the American College of Cardiology's 63rd Annual Scientific Session in Washington, D.C., according to RedOrbit.

"The heart doesn't work as hard in space, which can cause a loss of muscle mass," senior study author James Thomas, MD, Moore Chair of Cardiovascular Imaging and Lead Scientist for Ultrasound at NASA, said in a statement. "That can have serious consequences after the return to Earth, so we're looking into whether there are measures that can be taken to prevent or counteract that loss."

Astronauts on the ISS used ultrasound machines to get data and take pictures of their hearts before, during and after missions, according to the study.

Results indicated that the heart became more spherical by 9.4 percent, which could mean in locations of low gravity the organ doesn't perform as efficiently, according to RedOrbit.

Previous studies have shown astronauts have been exposed to a number of health related issues when taking long space trips, like bone density loss and visions anomalies.

Researchers are hoping results will help them see how an 18 month or longer spaceflight would impact the health of astronauts.

The heart's spherical shape reportedly returns back to normal once astronauts return to Earth however.

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