Posted by: Jack Mankin (MrBatspeed@aol.com) on Thu Jun 22 07:12:47 2006

>>> You and ny man both have info very good info, But whAt is the difrence between two? WHaT generWtes more power, why? Where does rotation start? Up in the hips,down to thefeet, or from down to the feet upinto in the Hipps?? <<<

Hi Grand Slam Man

On this and many other sites, coaches have presented varying views on what powers hip rotation as well as the axis they rotate around. I have not read all of Nyman's views, but from what you posted here, I would have to say I am in more agreement with his position than Yeager.

Yeager's model emphasizes using the momentum attained during the stride to rotate the back-hip around a blocked front-hip. This places the axis of rotation at the front hip (like a gate swinging on hinges). In the Nyman post you presented, he does not even mention linear momentum as a factor in hip rotation (I agree). It appears from this post that he believes that contraction of muscles in the pelvic region is solely responsible (I disagree).

Nyman goes on to state, "the foot and leg are in support of the actions of the muscles in the pelvic area give the appearance/impression of bracing up on the front side." For hip rotation to straighten a flexed lead-leg it must rotate rearward to straighten the leg. In other words, the lead-hip could not remain stationary (or blocked). This places the axis of rotation at the base of the spine - not at the lead-hip (as Yeager suggests). With the hips rotating more evenly about the spine, it would closer resemble a "revolving door" than a "gate swinging on hinges."

My main disagreement with Nyman's post is his contention that the legs' role is to support the hips but not aid in their rotation. Based on tests I have conducted, it is the combination of pelvic muscles and torque supplied from leg drive that induces hip rotation.

In the original 'Final Arc' video, we had a batter swing a bat while sitting in a swivel chair to show that a forward weight shift is not necessary to generate rotation and bat speed. Sitting in the chair prevented any forward transfer of weight (no linear momentum) and placed the axis of rotation at the spine (of course, some linear theorists might say he was "spinning"). A number of my students that performed the test were surprised that they could generate bat speeds about equal to their swings with a stride.

Try the basic test yourself. While sitting in a swivel chair, let your legs remain relaxed and use only the pelvic muscles to generate hip rotation. Then use the drive of the legs to aid in rotating the hips. I think you will find the legs add substantially to rotation.

Jack Mankin