Astronauts in space might have a tougher time exercising due to decreased blood vessel function.

According to a new study conducted by researchers from Kansas State University, astronauts aboard the International Space Station (ISS) have a 30 to 50 percent exercise capacity decreases in long-duration spaceflight because the heart and small blood vessels are not as effective at transporting oxygen to the working muscle.

“It is a dramatic decrease,” Carl Ade, assistant professor of exercise physiology at Kansas State University, said in a statement. “When your cardiovascular function decreases, your aerobic exercise capacity goes down.

“You can't perform physically challenging activities anymore,” he added. “While earlier studies suggest that this happens because of changes in heart function, our data suggests that there are some things happening at the level of the heart but also at the level of the microcirculation within capillaries.”

The new research is expected to be used to help Earth-bound clinical patients with heart failure, as well as helping to improve astronaut health and provide information for future long-duration spaceflights, according to Ade.

During the study, nine astronauts established an exercise capacity by performing a stationary bike exercise test several months before they were launched to the ISS for about six months.

The researchers measured a variety of statistics including oxygen uptake, cardiac output, hemoglobin concentration and arterial saturation to show how effectively the body transports oxygen to the muscle mitochondria. The astronauts were then asked to perform the same bike test within a few days of returning to Earth.

Astronauts aboard the ISS are tasked with a variety of physical duties including opening the capsule door to helping a fallen crew member.  Other tasks include performing emergency landings on Earth or performing extravehicular activities on the surface of Mars.

According to Ade, more research is needed on the way microgravity changes the interaction between blood vessel capillaries and red blood cells.

“This decrease is related to not only health but performance,” Ade said. “If we can understand why maximal oxygen uptake is going down, that allows us to come up with targeted interventions, whether that be exercise or pharmacological interventions.

“This important new information can help these astronauts and prevent any adverse performance changes in their job,” he added.

While the research benefits astronauts in preparing for long-duration trips to space, it may also shed light on the blood vessel functions in older patients or patients with heart failure.

“We have seen similar situations happen with heart failure and with aging,” Ade said. “If we can better understand what is happening in the astronaut and how to prevent it, then we might be able to do the exact same thing in a patient who is older or who has heart failure.”

The study was published in the Journal of Applied Physiology.