Pulling the rear leg(junzuki)

[mezusmo]

Hi

While stepping in junzuki i am instructed to have the feeling of pulling my rear leg forward as opposed to pushing of the it.While doing this i still get the feeling i am pushing off the rear legas well as pulling( it seems impossible not to have this feeling).Is it not true that even though on has the feeling of pulling the leg there is a push taking place?I am instructed that one pull's the rear leg as it is faster but i still get the feeling there is a connection to the ground with the foot and a push takes place.We see sprinters take off from their 'get set' position with a push to propel them forward in the name of gaining speed so what i am asking is do we truly rule out a push?

Thanks

[jaronlegel]

Hi Martin,
There is a reason why we don't push off. It has to do with keeping your balance. Normal walking is a certain push off of the behind leg, as if falling. The same is done with running. In Budo you need to keep your balance. That is why you see in old "samurai" movies that they run so weird.
So yes you pull your "behind" leg. Maybe a good comparison is when you tread on hot coals or a nail with your foot. You don't want to push off since then the nail will penetrate even more, so you pull that foot up.
So you bring your "back" knee as fast as possible forward.

Just my two cents,

Jaron

[wadoka]

My tuppence worth:

My take on this is that the overriding principle is not to overtly "kick" off the back foot, meaning not to push from the ball of the foot with a highly raised heel. However, I bet in reality if you had a slowed down video footage of everyone then I am sure that we are not all perfect, but it doesn't affect what we are striving for.

Given the geometry of junzuki, and if we forgo the imaginative descriptions that we sometimes use to convey our message, we are a set of joined up Meccano pieces.

From junzuki, to move forward, the initiation is from the front leg no longer playing a role in holding the structure in place, eg taking the brake off. The rear leg is still connected to the floor and that is connected to your centre, so the weight drops but the resultant force is going forwards. Because the rear leg is straight (not too loose) then the centre arcs down and forward.

You catch this moment, the rear leg/foot has made its contribution and then you can pull through.

Very simplistic and idealist I know.

[mspain]

Does pull with the feet; push with the hands have anything to do with this?

Mike Spain

[mezusmo]

Thank you for your replies.

[shtook]

I remember the Perry's gait analysis from studies (see link). It describes phases off the normal (walking)gait: pages 7 & 8.

http://www.google.nl/url?sa=t&rct=j&q=& ... GQ&cad=rja

Junzuki is a little different from walking but some of this may still help in thinking about the movement. For instance at the-trunk-glide-phase in normal walking we can rely on momentum. In junzuki we start with trunkglide through relaxation and pulling the body (trunk) over the front foot. The rear leg is just before early swing-phase at this time, a little stretch in that hip just before the rear foot lifts off helps propel the leg in to swing.

It helps me thinking about movement, doesn't necessarily help in quality of movement... I'm working on a smooth landing at the moment. Perhaps if my foot lands a little further I stop stomping and my junzuki is less rigid?
Back to lurking. Thanks form the great forum.

Casper Baar

[JuhaR]

How about contracting - expanding as a part of the process? From junzuki stance you - as Gusei puts it - project your intention forwards through your front hand, and do a lot of other stuff after that. What if instead of pushing with the back leg you kind of contracted towards your center, and then expanded again? Projection of intent, slight unbalancing towards your front, a quick contraction, followed by a quick expansion?

I also believe that those in the know can use their core as the "motor". I can't explain this as I have only nudged on this phenomenon once or twice, and quite accidentally. At least on one occasion I unconsiously somehow expanded my lower abdominal region outwards (to the front, and to the sides) when initiating the movement, and then kind of pulled it quickly back. I felt like only my tummy was active, and everything else just followed completely relaxed. Both my upper and lower body were completely loose, all "power" was concentrated in my stomach. Don't know, perhaps I got it all wrong, but it felt "right".

[claas]

Hi,

In junzukidachi put skateboards under your feet and see if your stance stays the same, becomes longer or becomes shorter. If the feeling is the same as when it becomes shorter (opposing pulling friction forces), then you really don't need to push at least backward (but probably a little uppward). If you let the front knee bend without pulling with it in order to move forward, you have to push with the back foot, what comes to analysis of forces.

However the point in telling not to push with the back leg is not in correct physics terminology but more in learning to also pull. If you take the skateboards back, standing still with them requires use of the pulling muscles that are required for junzuki.

[Gusei21]

Lasse,

The bigger question is this.
Why is it that people who really know what they are doing says to never push off with the back foot....
What does that mean?
Do we still have to push off a little? (of course).

If you push off with the back foot then you will be slow.
So then what should we be doing if we aren't allowed to drive off our back foot?
Another way of saying it is - what am I doing that makes me faster than you.
Can you be as fast as me? Of course. What do you have to do to get there?
That's the problem you have to solve...

[claas]

Hi Bob,

Lasse,

Here you go...you don't push off the back leg...
http://www.youtube.com/watch?v=SRRrKPZTDvc

(Taken from the thread "Body Mechanics".)

This is a good demo how it should look like and what it means when it is said that "you don't push with the back leg". If we analyze the forces here, it is like this even in the video:

If you let the front knee bend without pulling with it in order to move forward, you have to push with the back foot, what comes to analysis of forces.

This happens when Inoue says that you drop. That is the reason why his drop is not directed down but is falling down to the forward direction. The direction of acceleration is the same as the direction of a vector sum of gravity and the contact forces between his feet and the ground. In the beginning it is obliquely forward (slightly downward). (I won't get into sideway "zigzagging", because that's not the point here, I guess...)

I also mentioned this gaining from dropping a little that Inoue does like this:
(from the Body Mechanics thread)

Also one thing that in reality has to be taken into cosideration is falling in the beginning.
(...)
Falling allows you to use your structure for accelerating as well. Already one inch is a lot and it's also almost invisible.

Perhaps the reason why it is said that the performer shoudn't push, when there is a push happening anyway, is that the feeling is more of "it happens" instead of "you make it happen". So I guess everyone in this thread agree. It's just about teaching terminology vs mechanics terminology. Just because there is a pushing force in the back leg doesn't mean it is better to say "you should push". Typically that would be interpreted as a sudden tensing of the calf and the front part of the thigh. A jump. An active push.


I apologize this being difficult to read, but I guess learning both the physics and the body skills to the point that one can put the "don't push with the back leg" in the real context demands work to do. This physics part is a lot easier but still it is also a study in itself.