Astronauts Grow Taller in Space

A temporary increase in height is a peculiar side effect of spending time in a microgravity environment. This phenomenon is not due to bone growth, but rather the expansion of the spinal column. On Earth, gravity constantly compresses our vertebrae, but in space, the discs between the vertebrae are free to expand, much like a spring being released. This can result in a temporary height gain of up to 3% of an astronaut's original height, which for a 6-foot-tall person could mean an increase of about two inches. This change typically occurs over the first few days in space.

This spinal elongation, while seemingly a benign curiosity, can have its downsides. Many astronauts report experiencing back pain and discomfort as their bodies adjust to the changes in their spines. Furthermore, this increase in stature is a significant consideration for mission planners and engineers, particularly when it comes to the design and fit of spacesuits and the internal dimensions of spacecraft. A suit that fits perfectly on Earth could become uncomfortably snug in space, potentially impeding an astronaut's mobility and ability to perform tasks.

The study of how the human body adapts to space began with the very first human spaceflights, with agencies monitoring the effects of microgravity since Yuri Gagarin's historic journey in 1961. Upon returning to Earth's gravitational pull, the spine gradually recompresses, and astronauts return to their pre-flight height within a few days. This rapid reversal underscores the profound and immediate impact of gravity on the human musculoskeletal system.