The way one lifts weights for bodybuilding purposes is quite different than from weightlifting, or any other sport out there. For bodybuilding, the goal is to isolate the individual muscles one wants to promote growth in. This is done by contracting a muscle, and the weight then moves as a result of the contraction.

The mind sets the intention for the muscle to contract, the brain tells it to contract. The synergist muscles connect the contraction to the weight/resistance being used. Thus, the contraction is the first step, and as a result the full motion happens and the force is exerted against the resistance.

Powerlifting form is about efficiency, the exact opposite of bodybuilding. Generally, we want to create the most structurally sound positions before moving the barbell, and maintain them until the lift is completed. Tightness plays a huge role; we want to use everything we can (the barbell, the floor, a belt, wraps, whatever we have) to create more tension in the body before the lift begins, and then release it all at the time of the lift. Minimal bar movement and maximal force production.