I got a shake weight for Christmas because I really wanted to try it, and it wasn't that expensive either.  They say on TV that 6 minutes is like a 1/2 hour using the shake weight.  Anyway, thought it would be easy.  I was SO wrong.  I can do 50 SECONDS before I have to stop because my body cant physically do so much.  My cousin who is (into sports and) well-known , tried it and agreed it was harder than appeared.  I was also thinking that on the commercials for it, the people demonstrating it aren't the average person....they are well fit.  If anyone out there can do a full 6 minutes in a row please post/comment on it! 

The quality of it is less than it seems, IMO< ---the ends are 2.5 pounds each, and the bar inbetween is a type of plastic.  I thought the quality could be better but overall it works, just not able to do even a minute yet.  Much harder than it looks.

Melissa.