when i trained with a power lifter he taught me to do that, but is that just a power lifting technique? is it better to keep the back more flat if trying to isolate the pecs? Pinching the back does help me get more weight up, but is it as good for pectoral developement? Pinching the back seems to involve my lats and back more.
What do you do?
Bump
In my opinion, it adds stability to your base. Your chest will be higher, so you will have less ROM on the press. This is a great advantage for a powerlifter. It really depends on what phase of your training you're in. In a strength phase (neural adaptations), use the technique to move more weight. While in a hypertrophy phase (increasing muscle fiber size) use less of an arch to isolate the pecs more.