Push-off with the back leg???

There are lot of things you do not see!!!!

I don't see it either.

You don't see it because you don't do it. Same as pitching. Anyone who says you do is lacking knowledge.

The back leg push is just one other style of hitting.

The real power generation is the cantilever effect of the upper body.

This even allows a one legged batter to hit reasonably.

The last clip I believe shows a push. Watch the knee it will load. I believe that this is what is being described as a back leg push.

I don't pretend to know a lot about hitting, but I am an engineer. A body at rest does not magically start moving forward as all of these video clips show....so tell me how does this happen....

A batter in his stance is not a body at rest.

The stance establishes an amount of potential energy.

The most efficient direction of that potential energy would be downward, as affected by gravity.

The swing employs a certain amount of motion established by the hips which due to string tension causes the bat head to travel in a somewhat circular path.

quote:

Originally posted by BlueDog:
There's been alot of talk lately about MLB hitters pushing off from the ground with the back leg....

Where's the push-off from the ground with the back leg?..I don't see it...

Looks like the back foot is being dragged forward to me...

If there is a push-off with the back leg, the back toe would be dug in, not being dragged up and forward and even getting airborne........

Now, something is pushing/pulling the backside, but, I sure don't see a push-off from the ground....

I see the back toe being pulled, instead...

Blue,

I push with my back leg from the time my front foot hits the ground until my belly button gets to the direction of the blow. Once the hands start forward after the elbow slots, the back leg will be pulled forward from the power of rotation. The more the up swing or the more out front the ball is struck (either or) will dictate how far the back foot will move and in what direction. I believe Lee and Pujols both do what I do. As far as Mays goes, the combination of and upward swing, inside pitch and his big lunge or dive forward caused his foot to leave the ground that much in the clip shown, IMO. I can't tell much from the clip of Manny, since it is later in the swing before it starts. I believe you can push, pull, or turn your hips open, some even use a combination of two or all three of those.

quote:

Originally posted by Quincy:
A batter in his stance is not a body at rest.

The stance establishes an amount of potential energy.

Huh......It is obvious you do not understand physics. OK I will simplify this.

Any movement of a batter (body at rest) has to be offset by a force that must be applied through his feet.

There is no pushing with the back leg. What it does do is collapse slighly to set up support for the upper body rotation. It is similsr to pitching. The back foot is pulled fprward by the hip rotation. To try and leave it back would impede the hips.
If the back leg pushed it would make it hard to hit a ball and the upper body would lung foward instead of staying back.

I agree with BOF. The feet stay planted as much as possible to create the base for the rotation of the upper body. The lower body is a stablizer or folcrum around which the upper body is developing max force . Yes there will be some movement but no pushing.
The force applied to the feet is the counter reaction to the rotation of the upper body.

quote:

Originally posted by BobbleheadDoll:
There is no pushing with the back leg. What it does do is collapse slighly to set up support for the upper body rotation. It is similsr to pitching. The back foot is pulled fprward by the hip rotation. To try and leave it back would impede the hips.
If the back leg pushed it would make it hard to hit a ball and the upper body would lung foward instead of staying back.

I push with my back leg, it is after the hips start to open and as the front leg starts to firm up and the glute helps to pull the hips around. The front leg being on the ground and solid, keeps the body from moving forward. If you push a person on a swing, the swingset doesn't move but the swing moves around the bar to which it is attached. It is the same principal. If your hips stayed closed, you would move forward even if both feet were on the ground. This is how many young hitters start out and have to be taught to use their hips.

Tim Lincicum pushes with his back leg early and late, most just push late (if they push) to get over their front leg and to complete the hip turn. Some people characterize this as "the hips thrusting backwards". IMO, one hip does, but the other thrusts forward. Many Lefties don't complete this back hip thrust and that is why they don't usually throw as hard and why they have so much natural tail on their fastball.

OK this is getting dangerous - a pitching guy wallowing with the hitters. I am going to go with PTOF as far as explainations of what is going on. I can add some physics and see if it makes sense.

The guy who taught my son to hit always said.

1. Hit off a firm front foot.
2. Hips lead the swing and create power.

Now if all of this is true and PTOF is correct then the physics would work as follows:

Looking down from above on a right handed hitter the swing MUST be initiated with the rear foot which would drive the right front hip to accelerate, this is the only way to initiate the swing as this is the only place the force can be applied to get the hip moving. The left front hip then is rotating back against the front foot which has to be pushing back otherwise the whole body goes into forward motion. The forces would have to be equal and opposite to generate rotation and if one is less than the other then the body begins to move in the direction of the lesser force. (if you assume a symetrical body)

Obviously there is all kinds of other stuff going on but the basic physics have to be as I have described as there is no other way to get the hips moving.

The bottom up approach is great if the batter is swinging upwards.

A good swing takes advantage of the raised bat and casts it down through the zone.

A batter can apply all the movements of the swing (weight shift, swing and hip turn) while standing on one leg.

quote:

(weight shift, swing and hip turn) while standing on one leg.

Weight shift if he jumps up, back, or forward. You can certainly swing and turn your hips while standing on one leg, but weight shift??? From where to where?

On one leg, weight shift can be felt from shoulder to shoulder.

Afterall, the machinations of the swing have the sole objective of producing bat speed.

Keeping the swing simple to its most productive movements creates the quickest swing to perform as well as producing the most bat speed.

If you are pushing with your back leg, you are performing in a more linear style. Though effective quite often with adequate hip turn, it takes longer to perform the swing.

There are many styles to swing a bat, some take more time, some produce more bat speed.

quote:

Originally posted by Quincy:
On one leg, weight shift can be felt from shoulder to shoulder.

Afterall, the machinations of the swing have the sole objective of producing bat speed.

Keeping the swing simple to its most productive movements creates the quickest swing to perform as well as producing the most bat speed.

If you are pushing with your back leg, you are performing in a more linear style. Though effective quite often with adequate hip turn, it takes longer to perform the swing.

There are many styles to swing a bat, some take more time, some produce more bat speed.

So...what would you say Mays is doing?

Mays is using a linear style. His entire body is moving on a line to contact with the addition of hip turn.

quote:

If you are pushing with your back leg, you are performing in a more linear style. Though effective quite often with adequate hip turn, it takes longer to perform the swing.

Since I am reading the pitch while pushing with my back leg. How can it be taking longer? I am also creating more stretch between upper and lower body...which creates more batspeed.

quote:

Originally posted by Quincy:
Mays is using a linear style. His entire body is moving on a line to contact with the addition of hip turn.

I agree! He is creating his momentum with a push forward and then turns his hips by stopping his momentum with a bent, open, front knee and then completes the turn with a locking of the front knee.

If you are pushing with your back leg, you are apparently moving forward. If you are reading the pitch while moving forward, you have already committed your swing to a certain area that must be adjusted on the 'fly'. This leads to less than good contact, if any at all, most often when large adjustment is called for.

Creating stretch and potential energy at this point is too late in the process since the bat head is already committed by the forward movement.

It would be similar to standing upright in the stance and then dipping your hips only to raise them again.

A 'downhill' swing is far more efficient.

quote:

Originally posted by Quincy:
If you are pushing with your back leg, you are apparently moving forward. If you are reading the pitch while moving forward, you have already committed your swing to a certain area that must be adjusted on the 'fly'. This leads to less than good contact, if any at all, most often when large adjustment is called for.

Creating stretch and potential energy at this point is too late in the process since the bat head is already committed by the forward movement.

It would be similar to standing upright in the stance and then dipping your hips only to raise them again.

A 'downhill' swing is far more efficient.

No, my back hip is moving forward, but my head and body do not.

If you are not pushing with your back leg...you will be spinning on your back toe and will get only half use of your legs as a power producer.

I don't know of any power hitters that have a downward swing nor can I think of any good MLB hitters that swing down to the ball. Maybe down to the plane and then up, but that is a product of where they start their hands in their pre-swing.

The swing process is only to the 'plane' of contact.

Once the bat enters that 'plane', the control phase of the swing is over. Just holding the bat during hip turn will produce additional bat speed in the bat's circular path.

Swing the bat to just in front of your body and add hip turn. You will feel the bat speeding up in your hands. This is what is described by the term 'turning on a pitch'.

With the popular swing styles used today, batters who exercise good hip turn will hit the ball foul for a good distance.

I understand the swing that you are describing. I used that swing in stick ball to hit balls on roofs. Stick ball bats were not end heavy as bats are.

Because the weight of the bat head assists in creating bat speed, swinging up is less effective.

quote:

Originally posted by Quincy:
I understand the swing that you are describing. I used that swing in stick ball to hit balls on roofs. Stick ball bats were not end heavy as bats are.

Because the weight of the bat head assists in creating bat speed, swinging up is less effective.

It's a good thing Ted Williams and Babe Ruth and Barry Bonds didn't know that.

quote:

Originally posted by powertoallfields:

quote:

Originally posted by Quincy:
I understand the swing that you are describing. I used that swing in stick ball to hit balls on roofs. Stick ball bats were not end heavy as bats are.

Because the weight of the bat head assists in creating bat speed, swinging up is less effective.

It's a good thing Ted Williams and Babe Ruth and Barry Bonds didn't know that.

Hahahaha

Ditto.

"The only difference between the baseball swing and the golf swing is the stride."

- Babe Ruth

Nothing about the back leg.

I never played stick ball with Williams, Ruth or Bonds.

quote:

If you are not pushing with your back leg...you will be spinning on your back toe and will get only half use of your legs as a power producer.

I think a clarification is in order, here...

I'm thinking you can push with the back leg with the glutes, hams and other muscles and not push-off the ground....

What I'm talking about is a push-off with the back leg from the ground...That is what I don't see happening....

I don't see the back foot being involved in the push....I see it being pulled up and forward....And, in some cases, sideways...

quote:

....the weight of the bat head assists in creating bat speed, swinging up is less effective.

I agree.....

Another reason I don't believe the back foot pushes off the ground....

The bat barrel is dropping when the back foot would have to be pushing...

quote:

Originally posted by BlueDog:

quote:

If you are not pushing with your back leg...you will be spinning on your back toe and will get only half use of your legs as a power producer.

I think a clarification is in order, here...

I'm thinking you can push with the back leg with the glutes, hams and other muscles and not push-off the ground....

What I'm talking about is a push-off with the back leg from the ground...That is what I don't see happening....

I don't see the back foot being involved in the push....I see it being pulled up and forward....And, in some cases, sideways...

I agree that Chipper does not push with his back leg at the end of his swing, but he is riding his back leg while he closes his hips and as they start to open. He starts with closed hips and strides open, so the momentum of his hips help to pull his back leg through, but he has to be pushing against the ground to start the opening since all of his weight is on that leg. His arm action helps to keep his weight back and to keep his stretch until the last moment.

Chipper also closes his upper body more than most hitters and that momentum adds to the pulling of his back side and that is an addition to his power source. Also, it would be interesting to see a line drive swing and see where his back foot goes. It may be the same, but I would think it wouldn't come as far off the ground.

quote:

The bat barrel is dropping when the back foot would have to be pushing...

Yep! The bathead is falling while he is striding.

From the time the hips get to open until contact the bat path is up in Chippers swing. IMO, the weight and direction of the bathead (down and back, to start the swing), helps to keep the weight back and keep the stretch as long as possible and will also help with batspeed. The path to the ball however is up and through, not down and through.

I've tried to stay out of discussion since...

My 2 cents, I've never taught a player to push off of their back foot. In hitting, I never thought about it. Is there some resistance? Sure, and the same as walking or ... However, I think that purposly thinking push off is similar to those other "thoughts" that impede the swing process.

Long story short. One of my Dads brought in an instructor in the winter/spring of 2006. The Dad owns a barn and our team hits there every winter. One primary point this guy brought in was the push off. I've never had so much trouble getting the players back into a groove AND my team never got off to such a poor start.

I want you to think about this. Take the move Elvis used when he was on stage. Now, use that comparison to the front knee pointing in or hip load and then, the rear knee following. Use that mental image and look at some pro video. Now try it. You won't feel yourself push off the back foot AND you will be very quick with the hips.

Some video for this discussion and I'll take a hike again. It is refreshing to see a good discussion without all of the attacks. Thanks, I appreciate that.

Bonds:



Edmonds:





Pujos:



Lee:

quote:

Originally posted by CoachB25:
I've tried to stay out of discussion since...

My 2 cents, I've never taught a player to push off of their back foot. In hitting, I never thought about it. Is there some resistance? Sure, and the same as walking or ... However, I think that purposly thinking push off is similar to those other "thoughts" that impede the swing process.

Long story short. One of my Dads brought in an instructor in the winter/spring of 2006. The Dad owns a barn and our team hits there every winter. One primary point this guy brought in was the push off. I've never had so much trouble getting the players back into a groove AND my team never got off to such a poor start.

I want you to think about this. Take the move Elvis used when he was on stage. Now, use that comparison to the front knee pointing in or hip load and then, the rear knee following. Use that mental image and look at some pro video. Now try it. You won't feel yourself push off the back foot AND you will be very quick with the hips.

Some video for this discussion and I'll take a hike again. It is refreshing to see a good discussion without all of the attacks. Thanks, I appreciate that.

Bonds:



Edmonds:





Pujos:



Lee:

Coach,

I actually teach the "Elvis" move, but I teach to use the big toe and pad of the big toe to push off of to get the knees moving. The front knee moves the hips closed and the back knee moves them back forward. Once the bat is in position to go forward and the hips are fully open, I teach to punch the back knee in the direction of the hit. Now...I guess that can be characterized as pushing with the glutes, hamstrings or pulling with them.

Here is how I teach hip rotation; I put a 5 gallon bucket between the hitters' legs between them and the plate and have them touch the bucket with their knees, front first and then back while turning their hips. If you do this drill, you will feel the pressure on the big toe and pad of the front toe and you will also realize that the knee had to pinch in and toward the plate to reach the bucket. This drill needs to be done without the head or body moving backwards or forwards. It has been very successful for me.

powertoallfields, sounds like you're very close to what I teach. The exception then is that I think that the hips etc. follow the middle or core. I see how you can say what you want you hitter to feel after going out and doing it with the bucket. I'd suggest that you accomplish what you want. Still, and this is just my opinion, that same result might be gained from associating one knee "chasing" another. Please don't get me wrong on your drill. I do see very postitive things from it and would suggest that if you could find the right size buckets, it'd be great for all ages.

I'd ask you here if you've ever tried the playground ball? It is more of a presure on the ball with the knees and then, at some point, naturally, the ball will drop. I don't do this with them holding a bat to make sure that they are working on that issue. I guess you might deduce that in our hitting sessions, we break things dow a lot. I am guilty of overcoaching and I know it. I've tried to do better. Bluedog, are we similar or far apart on this. Also, I know you have some great stuff on this concept. Any you like OR potential pitfalls from these ideas?

quote:

Bluedog, are we similar or far apart on this.

Coach, we are similar.....

I don't use props, though....Just a kid and a bat....

And, I do believe the core muscles move the hips.....Not a push-off from the ground....

The "push" happens at the back hip during front hip c0ck. You can't "see" this in the Lee clip because his front leg is already near peak knee lift.

Look at the clip of Edmonds. Both of his hips are pushing against each other. His front hip resists rotation by turning the front knee inward. The front leg opens/uncocks and the "push" from the rear hip offsets the hips for complete "rotation" of the hips to follow if he so chooses to swing at the pitch.

quote:

Originally posted by XV:
The "push" happens at the back hip during front hip c0ck. You can't "see" this in the Lee clip because his front leg is already near peak knee lift.

Look at the clip of Edmonds. Both of his hips are pushing against each other. His front hip resists rotation by turning the front knee inward. The front leg opens/uncocks and the "push" from the rear hip offsets the hips for complete "rotation" of the hips to follow if he so chooses to swing at the pitch.

I agree and the back leg pushes/resists until the front heel touches and the bat starts to the ball. It is also what initiates the weight shift in my swing and what I teach, from 95% to 100% back leg to 50% both legs. It is the stretching of the rubberband. The rest of the weight shift is done by rotation and the "punch" at the end with the back knee (which uses the glutes, quads, core, hamstrings, lats).

What you are seeing is an adjustment to the ball coming inj not a push. The stride which I always had a big one but most teach to have a short one requires a shift and the back leg colapses slightly.
Once the front leg is down it just rotates as does the back foot. I always had as little lower body movement after striding as it set up the stable support of my upperbody as I swung the bat Too much movement makes it hard to make proper contact which is the most important thing when hitting a ball.
The back leg reacts to the force applied to the ball. The front leg is stationary and forms a 45% angle after impact giving you max power.
If you push off the back leg you will have problems with contact. The weight of the body is kept back.
Sounds a lot like pitching to me.

Tim doesn't push off the ribber. He has an abnormal stride wiich is 129% of his body height compared to most who are usually 77-85% of their height.

quote:

Tim doesn't push off the ribber. He has an abnormal stride wiich is 129% of his body height compared to most who are usually 77-85% of their height.

What makes him move forward??? If you don't want to call it a push then okay, but he is putting pressure on his back foot while keeping his weight back as long as possible. You can't stride without pushing off on your back foot...period. Your weight must be transfered to your front foot and the second you lift your front foot, the weight gets transfered to your back foot.

Below is a direct quote from Tim Lincecum.


"That just came naturally," Tim says. "My dad always told me to sit down on my back leg as long as I could and push off as much as I could. I'm trying to get as much out of my body as possible. I've got to use my ankles, my legs, my hips, my back. . . . That's why I'm so contorted and it looks like I'm giving it full effort when it's not exactly full effort."


I agree! Pitching and hitting mechanics are very, very close.

quote:

Originally posted by BobbleheadDoll:
What you are seeing is an adjustment to the ball coming inj not a push. The stride which I always had a big one but most teach to have a short one requires a shift and the back leg colapses slightly.
Once the front leg is down it just rotates as does the back foot. I always had as little lower body movement after striding as it set up the stable support of my upperbody as I swung the bat Too much movement makes it hard to make proper contact which is the most important thing when hitting a ball.
The back leg reacts to the force applied to the ball. The front leg is stationary and forms a 45% angle after impact giving you max power.
If you push off the back leg you will have problems with contact. The weight of the body is kept back.

I agree with what you are saying. I only use the word "push" in the context of this thread. Although it seems everyone has a different way of defining and using that word. I hate using that word too.

The better word to describe what's happening in the back hip is "resistance". There is tension there in the muscles. It may or may not always result in movement. Muscles can do work without changing joint angles. I hope Quincy has figured this out.

I talk to a lot of MLB pitching coaches and every one says that pushing off the rubber is a big myth. Yes the leg colleses but if it was pushing off it would straighten out again. The back leg has a part in the forward motion but it is a huge mistake to tell a pitcher to push off the rubber. I have several analysis of Tims motion and he doesn't push off the rubber.The power is delivered out front when his upper bady uncoils. I used to pitch Fast ball and you would think that you push off the rubber. Not even close. It was my front leg that took the punishment. When I finished a game my front leg was usually sore because it set up the release of my power as it straightened out. I also pitched BB as well and neither leg really felt sore after a game. My post foot collapsed, my hips rotated and my weight was back supported by the read leg. When I started forward the front leg was bent back and as I uncoiled the rear leg dragged slightly allowing me a stable base for the release of my power as the upper body did its thing. The front leg took the brunt of the pressure. That doesn't mean the back leg didn't play into the throw but it didn't push off. Tim accually reminds me of a fast ball pitcher with his gigantic stride. He also wraps back more than most because he is extremely flexible.

quote:

Originally posted by Quincy:
"The only difference between the baseball swing and the golf swing is the stride."

- Babe Ruth

Nothing about the back leg.

I never played stick ball with Williams, Ruth or Bonds.

A couple of things about this. One, on a drive, does the club travel up through the ball or down through the ball? Two, are you saying the back leg does nothing during the golf swing?

I do believe the mechanics of the hips and core are very similar. The only major difference is the swing plane.

quote:

The swing process is only to the 'plane' of contact.

To me, everything before the commitment to the ball is just preparation to swing. There are many, many ways to get to this point. However, there is one that is more efficient for power and average and that is the swing of Ted Williams in the latter years of his career. There are also several who have different variations of that swing, but his is most efficient. Some of the variations are Babe Ruth, Lou Gerhig, Stan Musial, Gary Sheffield, Jimmy Foxx. Exact replicas are Barry Bonds and Josh Hamilton.

If you want to learn to hit or teach hitting, watch film of those hitters and try to duplicate them with your own swing. Figure out what they are doing and why. What does it do to your swing?

quote:

Yes the leg colleses but if it was pushing off it would straighten out again.

The key is to hold your weight on it WITHOUT straightening it until the last possible moment. Resist the turn until the last moment.

quote:

I'd ask you here if you've ever tried the playground ball? It is more of a presure on the ball with the knees and then, at some point, naturally, the ball will drop.

Coach,

Are you talking about a kickball like they use in Elementary school?

quote:

Originally posted by powertoallfields:

quote:

I'd ask you here if you've ever tried the playground ball? It is more of a presure on the ball with the knees and then, at some point, naturally, the ball will drop.

Coach,

Are you talking about a kickball like they use in Elementary school?

Yes. The bigger of the two sizes that elementary schools use. Again, that is just a breakdown drill. I'm betting you know someone that has one of those balls so that you could give it a dry run yourself to see if it works for you. Like all drills, not all work for everyone.

quote:

Originally posted by CoachB25:

quote:

Originally posted by powertoallfields:

quote:

I'd ask you here if you've ever tried the playground ball? It is more of a presure on the ball with the knees and then, at some point, naturally, the ball will drop.

Coach,

Are you talking about a kickball like they use in Elementary school?

Yes. The bigger of the two sizes that elementary schools use. Again, that is just a breakdown drill. I'm betting you know someone that has one of those balls so that you could give it a dry run yourself to see if it works for you. Like all drills, not all work for everyone.

I tried it with a flat s****r ball tonight and can see where it would be helpful if I had the actual playground ball. It gets the feeling of turning to open the hips.

The back leg push happens after the back leg load and before the hips turn and the back foot is pulled. Look earlier. The push happens to get the hitter to hit into his frontside and not on his backside.look earlier. earlier than the turn. earlier.

quote:

but if it was pushing off it would straighten out again.

This is just not true. There can be push without the limb gong straight.

Some pics from a similar discussion:





Now, what are your conclusions based upon this slow motion video of 3 hitters?

quote:

Originally posted by CoachB25:
Some pics from a similar discussion:





Now, what are your conclusions based upon this slow motion video of 3 hitters?

Coach,

The only things I see different are the length of stride, the amount of head movement. The guy in the bottom clip is much more over his front foot and is pulling his hips through instead of pushing his hips open. Middle guy pushes/rides back foot to start and then lands on a soft front knee and finishes the hip turn with a push back with his front leg. Pujols does all three. Oh...and he rotates into foot plant.

quote:

The back leg push happens after the back leg load and before the hips turn and the back foot is pulled.

Swingbuilder, so you mean the back leg push is to get the weight moving forward and not meant to, in any way, push the back hip open?

quote:

Originally posted by CoachB25:
Some pics from a similar discussion:





Now, what are your conclusions based upon this slow motion video of 3 hitters?

These clips are misleading. Again, they don't show the WHOLE swing as I mentioned about the Lee clip. Pujols' and A-Rod's front leg are already on the way down.

Why not show the WHOLE swing?

Watch ARod's back knee. Why would he do this if it wasn't to support a "push" of the back hip/leg?



Pujols' back knee?



What are you conclusions based on the WHOLE swing? As swingbuilder said, look earlier.

XV, do you agree the back leg push does not open the back hip?

I'm trying to figure out how all of this is done with physics, maybe its because I'm young and naive, but I've learned that without your back leg helping get your back hip forward, then you can not be successful. I recently sprained my ankle in the first inning of a game, and played the rest of the game. I sprained my right ankle, and ruptured a ligament in the outside part of my ankle. I finished the game 1-4 after getting that hit in the first inning. My swing was completely different because i could not put any weight on my right ankle (back side). If what you are saying is true, I would've had no problem at all swinging the bat the same as I did before. I didn't even make decent contact with the ball the rest of the game. Please tell me how this could happen if according to physics and everything you're saying then I should've been able to hit just like nothing had happened.

It seems you had a bum wheel, yet made no compensation for the shortcoming.

If you were to put your feet close enough to each other to give yourself a sturdy base, you may have had better luck.

May not have helped you beat out any grounders, but you'd be able to get the bat around with no problem.

I see the knee come forward slghtly then go back to add load to the back side to get more momentum and power as the weight shift begins and creates the push off.

quote:

Originally posted by BlueDog:

quote:

The back leg push happens after the back leg load and before the hips turn and the back foot is pulled.

Swingbuilder, so you mean the back leg push is to get the weight moving forward and not meant to, in any way, push the back hip open?

In my swing and in the swing I teach, the back leg does not push toward the Pitcher, the big toe raises the heel and pushes the back knee more toward the plate. The front knee loads the hips and the back hip helps to fire the hips. If you look at the clip of Bonds on page two of this thread, you will see the push of the front and back knee toward the plate.

IMO, the dropping of the front heel and the raising of the back heel, start the weight shift process and rotation and the swing finish it.

The only push is the resistance of the back leg to the back loading of the weight. It does this to stabalize the lower half and to keep the back leg from collapsing too far.
A true push would mean the foot would leave the ground. The lower half creates a stable base for the loading and unloading of the upper half.
It is necessary to have both legs functioning in thyeir roles to stablize the lower half to achieve max power.