I've seen some guitarists put their hand above the bridge, or somewhere around there, and press their hand down when they are bending, why do they do this? Is it effective to the technique? If you need a vid I'll try to find one.
on a trem thats not set to the body, or blocked off, it will increase tension on the strings , raising their pitch.
You can do it easier by just pulling back on the neck while keeping the head in place. Can get some cool effects.
Look up Jeff Beck on youtube. He does it alot.
If you meant the technique like Marty Friedman, then its simply because of string muting. Doesnt want to accidentally touch the low strings when doing violent bends.
Thanks alot guys, you really helped.