When working out, you should always<em> rise and lower weights with slow and controlled motions.</em> It is to maximize the benefits of lifting and to prevent injury.
<em>As for the benefits:</em> Slow lifts can build muscles much faster than regular or fast ones. Rising or lowering the lifts in a slow motion forces the muscles to hold the weight longer. The particular muscle involved in the move stays activated longer. If one goes fast on lifting for example, momentum will do a lot of work which shortens the activity of the muscles. And the more a muscles works/is activated, the bigger it grows and the more it shows on the body. The goal is to fatigue the muscles before they fail. Muscle fatigue is a very good sign in building a muscle mass as the damaged muscles instigate greater growth. Finally, lifting/lowering slowly activates the skeletal muscles, they use a lot of energy and one burns more calories while using them.
Fewer accidents happen with slow lifting/lowering as one focuses on correct form and proper execution of each move; fast, uncontrolled moves can cause many injuries.
