NASA astronaut and Expedition 46 Commander Scott Kelly and his Russian counterpart Mikhail Kornienko enjoy the cold fresh air back on Earth after their historic 340-day mission aboard the International Space Station. Nasa TV

Exercise is the best way to grow tall. Another way could be a trip to space. Astronaut Scott Kelly has added two inches to his height after a year onboard the International Space Station.

The explanation lies in the disks of the spinal column. Where on Earth, the disks are slightly compressed due to gravity, this is missing in space and allows the disks to expand.

Kelly's year-long stay on the ISS is part of a mission to study the effect of spaceflight on the human mind and body. Testing began a year before he left and will continue for a year from now, his twin Mark Kelly being the control element.

Besides the loss of bone density and muscle mass, microgravity also affects the vision by influencing the optical fluids. Motor skills, changes in the internal microbiome, etc are other aspects which will be studied. When bodily fluids move into the upper body during weightlessness, it can result in visual changes and a possible increase in intracranial pressure, which need to be tackled before humans set out on long space missions.

As they mostly float in the spacecraft, astronauts do not use their legs and the bones in the legs, hips and spine experience a significant decrease in load bearing, writes NBC News. This leads to bone breakdown and a release of calcium, leaving the bone brittle and weak.

The size of the heart also is expected to decrease as it does not have to work as hard in space as on ground. Exposure to radiation can affect the lining of blood vessels and initiate coronary heart disease. On return to Earth, even simple acts like standing and walking can take time. Remember the last scene in Gravity?

Expedition 46 Commander Scott Kelly and his Russian counterpart Mikhail Kornienko returned to Earth aboard a Soyuz craft on Tuesday after a 340-day mission aboard the International Space Station. During their year long stay, the crew on ISS conducted 400 experiments into how the human body adjusts to weightlessness, isolation, radiation and the stress of long-duration spaceflight.

Kelly travelled around 230 million kilometers during his one-year stay on the ISS.