[mb6606]

The Speedchain is effective in building golf speed/muscles. Although Swing speed is worthless without lag. You need ample space and preferably use over a tightly woven carpet.

Speedchain's is a tremendous tool to protect and or rehab rotator cuff injuries. Figure eights, circles, tennis backhands, overhead throws are terrific exercises. The range of motion is unlimited (unlike bands).

Chain(s) is the only device I have found that can replicate exact sport motions while building strength.
If you are serious about speed training it is a good purchase.