User blog comment:AYET/Let's Discuss Chapter 733/@comment-1595565-20131226053307/@comment-2226235-20131226063843

The way it was phrased "they fell down" leads me to think your second suggestion is right. If it was a shockwave type attack that was powerful enough to defeat all of them, they would have been sent flying instead of just falling over. Something else caught my interest when I was rereading that page: there is a panel in the bottom right of the page that has someone saying that they had heard rumors about that. The view isn't good but it looks like Luffy's helmet and fake beard so it might be Sabo.