could you please explain how this 'pulley' system works?? i dont quite get the drawing...lol...you also said that once you understood the mechanics of the deadlift it improved your form...is there something i can read to understand the mechanics behind it?
Basically, when lifters who don't understand the deadlift view it as simply standing up they put too much emphasis on the front of their feet and wind up shifting their centre of balance forwards. It's as though they're trying to make it a quad-dominant lift like a squat. This is often why lifters round their back; they're not lifting with the proper muscle contraction.
The pulley system is just a name I came up with to explain the proper mechanics of a deadlift. Your posterior chain acts as a pulley system, with the origin of exertion being the hams/glutes.
Imagine a ski chair lift. They start at the bottom of the mountain where there's usually the heaviest, strongest gears and equipment. This would be the hamstrings/glutes -- the dominant muscles in a deadlift. The cable continues up the slope of the mountain (i.e. the back), and usually bends over the top of the slope and flatens out where it drops the skiiers off (i.e. traps).
When a deadlift commences, (ideally) the hamstrings and glutes contract and begin to pull on the entire posterior chain. As this happens, the elongated hams/glutes increasingly shorten from their stretched position and bring the back and shoulders up back to a parallel. The back does no actual pulling; it's simply a carrier for that cable.
While you'll certainly feel the back a great deal in deadlifts, you shouldn't be lifting with it. Let your hams/glutes pull the weight, and take your back out of the equation. It will get its work through isometric tension.
When I fixed my deadlift form last fall it was after reading a book on bodybuilding psychology. It taught me a lot about focussing on target muscles to better understand what you're really doing with your body. If you can visualize all the muscles involved, and how they're assisting each other, you gain a better understand of the muscular system, and it seems to make all lifts flow much better.