Does the word 'ugh have some other meaning in this context?
No, it just means be heavy. I find this sentence completely mystifying. Maybe it's a quotation.
Well, I will say this for it: the mystifying nature of the sentence sure makes it memorable. I won't be mistranslating this one any time soon.
Perhaps a reference to He Ain't Heavy; He's My Brother: https://en.wikipedia.org/wiki/He_Ain%27t_Heavy,_He%27s_My_Brother