Washington: Technologies developed for and aboard the International Space Station have benefited people on the ground, from improving workouts to helping us get a good night's sleep, NASA said as the orbiting laboratory marked 20 years of continuous habitation on Monday.

For example, NASA research has shown that exercise is the best way to reduce harm caused by extended stays in microgravity.

But this is not so easy, since barbells do not do much good without gravity.

Inventor Paul Francis worked with NASA's Johnson Space Center in Houston to perfect Spiraflex, springs that simulate the tension of lifting a weight without needing a physically heavy object.

The springs soon became the basis of an exercise machine that was used on the space station for over a decade.

Down on Earth, the same technology also powers exercise machines like the Bowflex Revolution and the OYO fitness portable gym.

But the effects of weightlessness do not disappear as soon as astronauts are back on solid ground.

After they return to Earth, NASA tests astronauts' sense of balance using a phonebooth-sized system. Making these measurements on the Moon or Mars requires something more portable.

Research into miniaturising this technology eventually resulted in a specialised scale that can help train people to improve their balance and predict when falls are likely, NASA said.

Lack of gravity is not the only difference that takes getting used to in space: the lack of a normal day-and-night cycle inside the space station disrupts important biorhythms.

NASA has performed extensive research into how different wavelengths of light affect humans and plants.

For example, plants on Earth take various cues from sunlight.

On the space station, the Advanced Plant Habitat uses an array of light-emitting diodes (LEDs) to simulate sunlight and optimise plant growth.

The plant habitat was designed in part by a company called OSRAM, whose Phytofy RL system uses a similar network of lights for plant research on Earth and is now commercially available for researchers.

Astronauts aboard the space station need special light of their own to maintain a regular sleep schedule.

Orbiting Earth every 90 minutes, the space station experiences 16 sunrises and sunsets every day, so its occupants' circadian rhythms get thrown off.

By installing LEDs that can vary the amount of blue light astronauts receive, a 24-hour day can be simulated.

After these LEDs proved useful on the station, Florida-based Lighting Science was interested in bringing these innovations to the market.

The company's "Awake and Alert" and "Goodnight" bulbs use the same principles as the station's lights to help people work through the day and then prepare for bed.

Space station testing is also helpful in other aspects of human health. For example, in 2011, biotechnology company Amgen teamed up with NASA to study a treatment for osteoporosis which causes bones to become weak and brittle.

Mice injected with an antibody to inhibit production of the protein sclerostin spent two weeks on the space station. Upon their return, the mice were found to have increased bone formation and improved bone structure.

In 2019, a sclerostin antibody treatment for fragile bones was approved by the US Food and Drug Administration.