I don't get it. If a swing is suppose to be free of muscle it should of one speed. so the feet matches up with the swing speed of the bowler. But, this article from USBC states differently.
"You may have heard in the past, “Raise the ball to throw it faster.†Today, it's actually the opposite and what’s left out is that you need to match the swing with the footwork for consistency."
http://www.bowl.com/Source/Source_Home/Adjusting_Ball_Speed/ Here's the whole article without videos.
Adjusting Ball Speed
If you drop an object from different heights, it falls at different speeds, in theory. Gravity works the same way until it’s effected by wind resistance or terminal velocity. Your bowling swing and ball speed are the results of gravity but should be seen slightly different in terms of consistency.
You may have heard in the past, “Raise the ball to throw it faster.†Today, it's actually the opposite and what’s left out is that you need to match the swing with the footwork for consistency. Most would raise the ball and, without realizing, increase their ball speed by throwing it faster with their arm muscles. In bowling we should learn to speed up or slow down our ball speed by speeding up or slowing down our footwork. In this same lesson you’ve probably heard, “Keep a loose, free arm swing.†By raising or lowering the arm swing and not addressing the footwork, you’re doing it all wrong.
Balancing the arm swing and footwork tempos are essential to elite performance and ball speed adjustments are necessary in today’s game. By raising or lowering the ball in the stance and repositioning the feet, we’re only doing half the work.
By raising the ball and not changing the footwork, the arm swing has to pull the ball down from the top of the backswing to accelerate. You’re simply lengthening the distance the ball travels and not adjusting the footwork to match. A bowler gets out of time when this happens.
By lowering the ball and moving back on the approach the swing distance is shortened and the feet have room to accelerate. Try this: Take a few steps. Go back where you started and take the same number of steps faster, you end up further away. Using this combination of lower ball position and further stance from the foul line keeps the swing and feet in time. Now we can have a loose arm swing and faster ball speed because our feet did all the work.
Lowering the ball in the stance and moving back on the approach increases ball speed
Now let’s throw the ball slower. Raise the ball in the stance and move up on the approach. The longer swing path matches the slower foot tempo.
Learn to adjust tempo by balancing the swing and footwork and by using the larger muscles in the legs you’ll be sure to keep a nice free swing.
Raise the ball and move up on the approach to decrease ball speed.