Question on the Bunce article, what is it with the rice?

Big Anthony Joshua should be back in the gym today throwing handfuls of rice in preparation for the day he fights a man that can move, avoid a punch and counter.
On Saturday night he would have needed a bag of rice to touch Fury, a sack of rice to get anywhere near Wladimir Klitschko
Is this some boxing term or is Buncey just talking out of his arse saying random words?