High-intensity exercise will be vital part of healthy space lifestyle

Long periods of time spent in space will require travelers to engage in high-intensity exercise to maintain their heart health, according to a new study published by the American Heart Association's Journal. The reason, according to the scientists, is the effect low-gravity existence has on the heart and its ability to keep up its function and strength.

Earth's gravity plays an important role in human heart health; every time you stand up, for example, blood is pulled toward the legs and the heart must adjust to keep blood flowing despite gravity's impact. In a microgravity environment like the one found on the International Space Station, however, astronauts don't experience the same effect.

In the absence of Earth's gravity, the heart doesn't have to work as hard to keep blood flowing and so the heart begins to shrink. The new study reveals that low-intensity exercise isn't enough to counteract the impact of long-term weightlessness on the heart; the findings were based on data from astronaut Scott Kelly, who spent 340 days in space, as well as long-distance swimmer Benoît Lecomte.

According to the researchers, Lecomte's 159-day swim wasn't enough to prevent heart shrinkage, nor was Kelly's six-days-a-week on a treadmill, stationary bike, and performing resistance training. Both lost left ventricle mass, though the scientists note that more research will be necessary to determine how the data may be applied to the general public.

The study's senior author Benjamin D. Levine, MD, explained:

The heart is remarkably plastic and especially responsive to gravity or its absence. Both the impact of gravity as well as the adaptive response to exercise play a role, and we were surprised that even extremely long periods of low-intensity exercise did not keep the heart muscle from shrinking.