What Causes the Hips to Rotate in a HL Swing?

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Jul 29, 2013
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QUOTE="rdbass, post: 529072, member: 2269"]
Do you think both rear and front side weren't 'engage' during this drill?
LittleLakerDrill.gif

Drill gives the hitter the feel of the rear leg/hip usage.
[/QUOTE]
The rear leg is engaged with the ground while the front leg is not. Closed chain vs open chain movements.

Notice how his rear leg externally rotates and the closed chain result is that the pelvis turns in the opposite direction.
Now imagine if he shift his weight from the back to the front leg. The rear leg would recoil back to a neutral position once it is disengaged from the ground...open chain action.
it's important to distinguish between actions that move limbs and torso in relation to each other, and actions that move limbs and torso in relation to the ground. I'd say engagement with the ground would be the difference....closed vs open chain.
 
Jul 29, 2013
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Taken from: Fortenbaugh, David. "The biomechanics of the baseball swing." (2011).
GRFz would be the scale measurement and BW=bodyweight

For the stride portion phase:

"Throughout the stride, the trail foot pushed with a constant GRFx of 21% BW
while the GRFz gradually rose from 86% BW to a peak value of 92% BW around −500
59 ms and then began to fall back down to 83% BW.

For swing initiation phase (not sure how he defined this but lets just assume it is close to what we call launch):

"This phase was marked by major movements in the lower body and moderate
movements in the upper body. The lead foot GRFx increased rapidly from 11% BW to
its maximum value of 50% BW while GRFy peaked at 28% BW around −123 ms. By
definition, the lead foot GRFz rose quickly during the swing initiation phase from 50%
BW to its maximum value of 130% BW. The trail foot GRFy also peaked during this
phase (24% BW) around −127 ms, while the trail foot GRFz waned from 47% BW to
34% BW."

For swing acceleration phase (after initiation until contact):
"The lower body was still very active during the beginning of the swing
acceleration phases, while very rapid movements in the upper body occurred just before
BC at the end of phase. All of the GRF dissipated during this phase, both in the lead foot
(Fx: −50% BW to −13% BW; Fy: 24% BW to −5% BW; Fz: 130% BW to 64% BW) and
the trail foot (Fx: 10% BW to −3% BW; Fy: 20% BW to 1% BW; Fz: 34% BW to 15%
BW). "
Very interesting. Especially when comparing max ground force rear vs front leg.
Does anyone still believe the rear leg is the driver?
 
Jul 29, 2013
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"Why not move in such a way that the large muscles get involved? "
Tell me more please.
During the stride, turn the pelvis perpendicular to the pitch while keeping the shoulders parallel to the pitch. At the same time point the front foot toward the pitcher. Stride against a bent front knee. From this position, the front hip is aligned over the knee which is aligned over the toes. Classic squat position. Now push against the front leg using the big muscles. Since the leg can't move the ground, the extension moves the front hip rearward creating greater core torque.

Turning in the hip joints-
whether in contact with the ground (closed chain) during the stride and internally rotating to "coil the hips" or externally rotating to turn the hips open, or externally rotating the front leg while off the ground (open chain), or releasing the rear leg from the ground and having it return to a neutral position (also open chain) ,
- is a small muscle movement and can't generate the power of the glute max and ham strings.
 
Last edited:
Jun 10, 2010
554
28
midwest
Meant to add to this thread but I got busy!
BobbyS... you left out some very important info on hip rotators.

With a flexed (hinged) hip...the glutes become internal femur rotators (moment arms).

So if a leg is stabilizing..such as the front leg when it catches the weight...they will become external pelvis on femur rotators on same side as the stabilizing leg.... as they go to hip extension. I believe at 90 degrees hip flexion... those glutes are considered a major internal rotator.. There are variations with the various degrees...but this is very important when looking at the hips in a swing. Also why teaching active glutes, hip hinging and extension is important imo.

The torque move mentioned...where the leg torquing into the ground and the pelvis moving in opposite direction....isn't part of the swing. Not saying you were saying that.... I say that because one twitter guru early in the year was touting that as if he had found the holy grail of hitting. That move is great for fielding and cutting but not part of the swing.

If you look closely at the two videos of TM and the boy...the weight bearing knee begins to internally rotate before that move. It gives up the internal rotation because the weight stays on the one leg...then externally rotates. That initial knee movement would of continued to go down and in with the rear hip still loaded. Thats my definition of rear leg driver. Really could care less if someone calls it forward fall though. What ever works for the girl.

To Julray...as far as the original question in this thread.... consider how the knee goes down and in... with a stable/loaded rear hip.....and how the hips move in the opposite direction of lateral spinal flexion (tilt, scrunch, ect)....and how that opens the hips, clears the hips ect. Easy to feel standing on one leg and tilting rearward.

From there with glutes activated...hip extension will take care of the rest of rotation. I don't even mention hip rotation with most of the girls.
 
Jul 29, 2013
1,199
63
Meant to add to this thread but I got busy!
BobbyS... you left out some very important info on hip rotators.

With a flexed (hinged) hip...the glutes become internal femur rotators (moment arms).

So if a leg is stabilizing..such as the front leg when it catches the weight...they will become external pelvis on femur rotators on same side as the stabilizing leg.... as they go to hip extension. I believe at 90 degrees hip flexion... those glutes are considered a major internal rotator.. There are variations with the various degrees...but this is very important when looking at the hips in a swing. Also why teaching active glutes, hip hinging and extension is important imo.

The torque move mentioned...where the leg torquing into the ground and the pelvis moving in opposite direction....isn't part of the swing. Not saying you were saying that.... I say that because one twitter guru early in the year was touting that as if he had found the holy grail of hitting. That move is great for fielding and cutting but not part of the swing.

If you look closely at the two videos of TM and the boy...the weight bearing knee begins to internally rotate before that move. It gives up the internal rotation because the weight stays on the one leg...then externally rotates. That initial knee movement would of continued to go down and in with the rear hip still loaded. Thats my definition of rear leg driver. Really could care less if someone calls it forward fall though. What ever works for the girl.

To Julray...as far as the original question in this thread.... consider how the knee goes down and in... with a stable/loaded rear hip.....and how the hips move in the opposite direction of lateral spinal flexion (tilt, scrunch, ect)....and how that opens the hips, clears the hips ect. Easy to feel standing on one leg and tilting rearward.

From there with glutes activated...hip extension will take care of the rest of rotation. I don't even mention hip rotation with most of the girls.
I think the torque move, the rear leg externally rotating while bearing weight and moving the pelvis in the opposite, is a part of the swing. It sets up the hip to shoulder separation and torque the torso.

The way the kid is swinging on one leg is entirely hip external rotation of the rear leg. I think two legged people could swing like this but I can't get past the fact that the explosive move to the ball doesn't start until the front leg is down and the rear leg becomes unweighted.
Add to that the extension of the front leg and you would get a resistance to pelvis turn..... unless.... the pelvis is turned via externally rotating the rear leg while the front leg is unweighted so the pelvis is perpendicular to the pitch direction. Now the extension of the front leg can be utilized to apply even greater torque to the pelvis and by moving it rearward from one side, assist in creating a more powerful swing.

Someone mentioned an offset car crash with a light pole and the torque and resulting spin. What if the pole was a car coming the other way and could not just resist like the light pole, but actually create counter force....?
The light pole could be seen as your stabilizing leg theory.
I'm promoting actively extending the front leg and it becoming that car coming the other way. The core is torqued, the muscles are stretched, then a force is applied to create more torque and everything moves instantaneously because all of the slack is removed from the system.
Stretch the rubber band to its max and then pull it a little more....

The whole load back side, coil in, or compress, and then unload, uncoil, or release the compression has its benefits but I think it leaves out the forward momentum. It starts from a stand still. I like the idea that the forward momentum can be loaded into the front leg and, via stretch shortening cycle, load that leg greater than just musculature, for a greater reaction by actually extending the leg against a properly oriented pelvis to create more rotational power to the shoulders....

I also spent time watching the one leg kid and Teacherman's one legged swing. I even tried is myself. What I see and feel is momentum created by throwing/rotating my torso and the resulting momentum can then be applied to the bat but only after it comes to a stop at the end of the movement. I dont thinkntheres a great deal of torque applied to the torso because I can't resist the turn very much. It feels and looks completely different than a 2 legged swing and there's no way to control timing or adjust. The front leg load allows adjustability.
I Iike how it turns the pelvis completely but then there's the whole thing where I'm still standing on one leg.
 
Last edited:
Jun 10, 2010
554
28
midwest
We will have to disagree on that torque move. Watching Knee movement/patterns... is an indication of whats happening in the hips. Watching knee movement with a pelvic marker... is an indication of whats happening with the relationship of the pelvic and knee...and you just don't see that.

If I may, I would suggest not getting too hung up on the metaphor one legged/two legged. Its a metaphor and nothing more. Its more confusing than useful. imo

Trying to figure it out using a one legged drill swing isn't going to help. In the one legged drill your feeling the rear side rotational axis, backside pivot points, creating a corner on the back side, earlier bat acceleration...as 4girlsdad said..the power of from the backside. Along with some of the other things you mentioned.

Having a stride and forward momentum...doesn't negate the ability to have those things.

We have a different perspective on the hips. I am not worried about hip torque. The pelvis (both sides) have to stabilize so the torso-core can torque.

Adjustability. Work on explosiveness-quickness with the various go drills for a while....then go to some live hitting. Did you loss the ability to adjust?

This is one argument I don't get. If I was training for a karate fight...and for 2 months I spared someone of average speed/quickness. Then went to a tournament and fought someone that was really quick. My visual mental perception and neuro-muscular circuit firing probably would not be up to snuff.
If I spared someone that was super quick for 2 months...then went to a tournament and fought the same person. My quickness and visual-mental perception and neuro-muscular circuits would be functioning at a higher level. Would I not be able to adjust in the fight?

I think both sides of the fence miss some important things about the body and its ability to adapt. JMO OMV
 
Jul 29, 2013
1,199
63
By adjustability I don't mean the ability to hit fast pitches. What I'm referring to is the ability to adjust mid swing to a ball that's not what the batter expected. In a swing that launches without a preload there's little adjustability. The swing takes too long and commitment needs to be made too early.
So by loading into the front leg I've created power from my rear leg and transfered is via momentum to my bent front leg. The front leg absorbs the momentum and converts it into potential energy via stretch shortening cycle. The SSC allows adjustabilty because there's a time over which the energy can be stored of around 1/2 second.
So what you see is hitters bending their front knee more (squatting) to delay the swing if the pitch is off speed.

I like the idea of the bent/loaded front leg because of the muscles involved. And I can build the muscles via Olympic style lifts. What are the high level weight training moves to build the hip rotators? And don't tell me they're the same Olympic moves because then you're training for the low speed karate fight....... They're not the same actions.
 

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