During the seminars I used to help out with, we did muscle testing using many different methods, on hundreds (I kid you not) of participants.
Using the word 'try' vs. 'do' - most of the times 'try' makes people weak while 'do' makes them strong.
Heavy metal music vs. classical - this was fun, heavy metal makes people weak while classical makes them strong too.
Fruits vs. a can of coke - fruits also make you stronger while coke (instant coffee too) makes you weak.
The caveat here is that these tests didn't always work, there'd always be people on whom it didn't work on but in my experience it worked on the majority of our participants.
What was more interesting were the ones on which it did work, but refused to believe it; they'd come up with a hundred and one crazy reasons why something that was happening to them couldn't be possible
