Though no personal experience doing them, its alot of weight to visualize trying to pop into the air like that, assuming that
these are the jump shrugs youre doing.
Your log ( i used to follow the one 2 years ago) always serves as motivation,so just trying to encourage you in the fact that im scared to attempt that exercise with that weight. Definately a unique excercise . never seen anyone attempt it, wish i worked out at your gym!