I hopped on one at a home show where they had a stand.
I wouldn’t put anyone with a family predisposition toward detached retinas on one, but the effect they induce is very interesting.
An extremely intense isometric contraction is the closest I can come to describing it.
Whatever you’re using to stabilise against the effect of the vibration, not so much whatever you’re using as the main movers, just the stabilisers, starts producing a cramping feeling extremely quickly. The feeling persists for quite some time after getting off the machine. If you were standing on it, walking is extremely difficult.
I honestly don’t know if they have value for developing specific aspects of physical conditioning or not.
All joking aside, these machines have been shown in scientific studies to have a MODEST effect in increasing the intensity. That’s only for exercises that can be done on the machines - walking lunges for 100 meters are out! As for increasing the intensity we all know how to do that without expensive machines, don’t we? Use a more difficult exercise or use more weight. Then say out loud, “Three, two, one… Go!” Yeah, if pushups aren’t getting the job done then try them on gymnastic rings… with a weight vest. For time.