>>13260502stomach vacuums.
It's a yoga/bodybuilder thing (Schwarzy did it often)
Strenghtens your transverse abdominis.
What the guy does is separating out your abdominal muscles (you have two strips, left&right, and some tendoms or whatever other shit straps it to your torso, hence the ab squares), which with some practice anyone can do, but it's more visible if you don't have gallons of fat in the front.
Stand shoulder with, a bit bent forward, breathe out as much as you can, and imagine pulling your stomach in (maybe even with some of your back, I personally feel it the most in my solar plexus area). It's easier to do this when yo are deflated (no air in lungs), sou you might need to practice some breathing before, to have enough oxygen in your blood so you can do his for more than 3 seconds.
