I read on http://zaazmovement.com/wp-content/uploads/2015/01/ZAAZ-20K-User-Manual1.compressed.pdf (mirror):
Standing on a ZAAZ vibration plate stimulates all parts of the body. 12 minutes on the machine engages over 90% of your muscles by causing up to 30 muscle contractions per second. Research shows that WBV can have profound impacts on circulation, weight management conditioning and pain relief.
Is it true that the using ZAAZ-20K engages over 90% of one's muscles? I couldn't find the research studies they mention.
Given that there are ~640-850 muscles in the human body, 90% of them sounds like a lot to me.