years ago, in a martial arts supply shop, I found a book on how to train yourself to snatch somebody's heart out of their chest. Of course, I bought it.
It advised filling a pail with a couple inches of sand, thrusting your hand into it- fingers extended, trying to 'grab' the bottom of the pail. When you could do it, add more sand, until the pail was full. Then start using gravel. And so on.