February 24, 2015

Catherine (Cady) Coleman, Expedition 26 flight engineer, performs calibrations on the VO2max Portable Pulmonary Function System (PPFS). The PPFS is located next to the Cycle Ergometer with Vibration Isolation System (CEVIS) so astronauts can measure their oxygen consumption while riding the CEVIS. (Credit: NASA)

Provided by Laura Niles, NASA/Johnson Space Center

In February, our attention turns to romantic matters of the heart. As American Heart Month, this month is also a time to focus on heart health and a perfect excuse to start working out to improve your physical fitness. Astronauts on the International Space Station are working to keep their hearts healthy too, and at the same time they are generating data to advance knowledge of health and fitness in space and on Earth.

Astronauts exercise regularly while in space to maintain muscle, bone, and cardiovascular health and fitness and to remain fit and strong enough to perform physically demanding tasks such as extravehicular activity. Scientists have frequently measured the effectiveness of that exercise during short spaceflights.

Now, researchers have assessed exercise on longer spaceflights with the help of astronauts on the space station, measuring their VO2 peak before, during and after missions of four to five months.

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Widely accepted as the best measure of cardiovascular fitness, VO2peak, also called VO2max, is a measure of peak oxygen uptake. That represents the highest amount of oxygen your body can use to produce energy during exercise. Oxygen is used by cells to provide the energy to perform work and a more aerobically fit persons cells take up and use more oxygen, explains Meghan Downs, senior researcher at NASAs Exercise Physiology Laboratory.

VO2peak is measured using a bicycle test, with astronauts starting at low intensity and gradually increasing pedaling resistance over a short period of time until they could no longer pedal the bike. The tests were performed three months before launch to the space station; after approximately 15 days in space; every 30 days throughout flight; and one, 10 and 30 days following return to Earth.

According to the results, published in the Journal of Applied Physiology, VO2peak decreased by an average of 17 percent by day 15 in space, but then gradually increased during flight. Most astronauts never recovered their preflight V02peak levels during the mission, but a few were able to maintain or even improve VO2peak during flight with frequent bouts of high intensity exercise.

Read more:

How astronauts exercise on the ISS