Hypersole: Foot sole sensitivity affects astronaut balance

Health Science

The Canadian Hypersole experiment studied astronauts to learn how their balance may be linked to foot sole sensitivity.

Background

Balance problems in astronauts returning from space are well documented. Some astronauts noticed that their foot soles tingled both during and after their time away from Earth's gravity.

These anecdotal reports piqued the curiosity of Canadian scientists, who wanted to learn more about microgravity's effects on the sensory system. The Hypersole research team investigated whether these reported sensations could be associated with changes in balance control in astronauts.

Researchers wanted to understand how foot skin sensors contribute to coordination and stability so they could eventually develop pre-flight training exercises and countermeasures to reduce recovery time upon return to Earth.

Simulation of a data collection session with Canadian Space Agency Astronaut, Dr. Dave Williams. (Credit: Canadian Space Agency)

Objectives

Hypersole aimed to:

 Impacts on Earth

As we age, the information sent to the brain from the soles of our feet becomes less reliable, which can lead to a loss of balance control and a higher risk of falls.

According to a Seniors' Falls in Canada report, falls are the leading cause of injury among Canadians age 65 and older. Nearly 1 in 3 seniors experience one fall per year. Research suggests that these accidents are the direct cause of 95% of hip fractures.

The findings from Hypersole add to the knowledge that could eventually be used to develop aids and corrective devices for older adults on Earth experiencing balance problems.

How it worked

Eleven astronauts participated in this study. Data for Hypersole was collected in three sessions: once before the astronauts' flight, once on the day they returned to Earth, and again three days after they landed.

  1. Researchers created a mould of each astronaut's right foot.
  2. During each testing session, researchers applied a vibration device through holes in the mould to measure the sensitivity of the skin on different areas of astronauts' foot soles.
  3. They also used filaments designed to apply different amounts of pressure to these areas.
  4. During each test, participants pressed a handheld trigger whenever they felt a sensation on their foot.
  5. Astronauts also took part in functional balance testing to reveal how foot sole sensitivity related to balance control.

 Results

The Hypersole experiment found:

  • Upon returning to Earth, some astronauts exhibited less sensitivity in their feet, while others showed increased sensitivity, particularly in their heels.
  • The astronauts with increased sensitivity had more problems balancing their weight correctly.

The researchers believe that this change reflects a weakened vestibular system, which controls balance from inside the ear. As an adaptation to microgravity, the nerves in astronauts' feet became more sensitive to maintain balance despite reduced inner ear information.

The balance system usually relies on vestibular, self-sensing, and visual information to maintain steady balance. To compensate for the lack of gravity in space, the body draws more information from the nerves in the feet.

Hypersole was developed after Canadian astronaut Dave Williams described a tingling sensation in his feet during and just after his mission aboard NASA's Space Shuttle Columbia. Dr. Leah Bent, Hypersole's principal investigator, was fascinated and decided to research the topic further in a science experiment.

Timeline

Hypersole's data was collected during four Space Shuttle missions between and .

Research team

Principal investigator

Co-investigator

Research team members

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