The video chronicles two days leading up to a professional boxing match, as Brandon Rios tries to make his weight limit.
"I don't know why, my body wasn't cooperating with me. It was just not following what I usually do. I don't know what it was," explains Rios.
Donaire vs. Nishioka and Rios vs. Alvarado happens Sat., Oct. 13 at 10pm ET/ PT on HBO. For more, watch the video above.