Am I correct in assuming it is near impossible for astronauts to stand still inside the ISS, even if their feet are secured under a blue IVA rail?
NASA astronauts Terry Virts' foot under a blue IVA rail
This video "Space Station Boost Proves Newton's Laws - All 3 of Them!" shows the astronauts while the station is being boosted into a higher orbit, and they are trying to remain still. While they are moving away from the camera do to the acceleration of the station, the are rotating on different axes either once they let go of something or they bring their legs up into a tuck.
Wouldn't the slightest muscle twitch or other movement would prevent them from standing vertically, unwavering, for any length of time.