It's the Star Trek TV shows' simplest, but most effective effect — have the actors throw their bodies in one direction while shaking the camera. Redditors took the time to stabilize these shots — i.e., show what they would look like if the cameras were actually still — and the results are ridiculous.
It should be noted that the inspiration for this video, and still the finest representation of how ludicrous these scenes must have been to film, comes from this gif by Mr_ Weller:
Who do you feel worst for? Uhura, who doesn't even get to fall down with dignity? Or that poor redshirt in the back-right who has to hurl himself across the deck?
[Via Gamma Squad]