How did you do that??? I thought videos could not be uploaded on EL&U.

@Cascabel: It's a GIF. (Upload a GIF on Imgur and copy-paste the link.)

I don't think there's a specific name for this movement, but it's usually called flexing.

@DecapitatedSoul Hunhh...I posted a Q on meta some time ago , and this was never suggested. Is this a new "get-around"?

@DecapitatedSoul - I would call it "expectorating".

@HotLicks: Only if you're a newbie :)

@DecapitatedSoul I am (or was) a pro photographer. I know what GIF means. I even know how to pronounce it!. I was unclear on how this works on this format when I was told before that videos could not be uploaded to this site. I seriously doubt you will be able to find another post on this site that does something similar...so I wanted to know how it could be done.

@Cascabel: Oh.... then I guess that the only way to trick the system. (The pronunciation part made me giggle :P, it's pronunciation is debateable!)

@DecapitatedSoul Choosy mothers choose...

What is a 'pec bounce'? Not knowing what it is supposed to mean, it sounds like what someone might call what's in the picture.

flexing your pecs, yep. I doubt this is jargon.

He's just flexing. He can do that because in strength training, muscles can literally tear in half, resulting in muscle splitting. That's why bodybuilders seem to have muscles others don't. They actually have the same number, but some have split, like his pecs have each split twice, so where I have one solid pec, his pec is split in three. I, and anyone, can localize flexing part of the pec, but since mine's all one piece, I don't get that effect. Since his has, when he flexes, you can see the splits and he can localize flexing one part without the other to create that rippling effect.

I'd have said he was twitching his pecs.

Somewhat more seriously, it might be said that his muscles rippled.

I find this question very annoying.

@HotLicks "mucles rippled"...shades of Rocky Horror and all that.

Not visible in the video, but the rippling likely reflects repeated finger squeezes. Just opening the arms does not produce that effect by itself.