do this, since he works at the gym he should be there to answer any questions of yours right?
ask him if your doing shrugs right, go pick up the 150's and then make sure he is kinda close, then drop one and then probably the other one too, but by his foot, then when he just realized that he almost lost his foot, say, boy, that juice that you told those girls I was on must not be working anymore.
good for a laugh, and almost positive it will shut him up
good luck