Saw this guy doing it today..and tried it for myself, and haven't felt that kind of strain in my abs in such a short excercise than today.
Basically you get on the decline bench, with a dumbbell or plate of some kind. I was using a plate of 25 and then 35..and basically you just do bench presses with the plate while keeping your back as parellel to the ground as possible. Basically then, the movement of the weight changes the direction that gravity pushes you down, and you're forced to hold that position while it changes.
If you've never tried it before, give it a shot
Basically you get on the decline bench, with a dumbbell or plate of some kind. I was using a plate of 25 and then 35..and basically you just do bench presses with the plate while keeping your back as parellel to the ground as possible. Basically then, the movement of the weight changes the direction that gravity pushes you down, and you're forced to hold that position while it changes.
If you've never tried it before, give it a shot