The “kinetic link” refers to the process by which speed or power is created in the golf swing. The golf-specific kinetic link can be visualized as a system composed of four segments and three links. The segments are the hips segments, the shoulders segment, the arms segment and the club shaft. The links are the muscles that connect each segment.
Before the backswing is completed efficient golfers are already starting the downswing from the ground up. As their feet push into the ground, forces are created which initiate hips segment acceleration toward the target. This should not be interpreted as a big, wild leg drive. In fact quite the opposite is happening. It is a very stable, controlled motion.
Once the hips segment reaches maximum speed, deceleration begins to occur. This “braking” action transfers speed to the shoulders segment, which accelerates to a maximum value usually twice that of the hips. As the shoulders segment reaches peak speed, deceleration occurs again. Speed is now transferred to the arms segment, which accelerate even faster. As the arms segment approaches impact, deceleration occurs rapidly transferring a huge amount of speed or momentum to the club. The club releases or uncocks into impact with maximum velocity.
reference — Chris Welch, welch-e technologies