How hard to stamp?

[Nanbanjin]

We have just been politely asked to move out of our Tuesday/Saturday training venue after causing damage to their wooden floor. We had been putting some cracks in the flooboards, but the straw that broke the camel's back came last Tuesday when someone smashed the end off one of the floorboards. The floorboard cracked about 20cm from the end where it butted onto another floorboard.
The venue was obviously unsuited to kendo, but is it really necessary to stamp that hard? My instructor tells me that you shouldn't really have to stamp so hard you break floorboards, and I tend to agree.
I was wondering whether anyone else out there has had any similar experiences.

[Pauly]

We have just been politely asked to move out of our Tuesday/Saturday training venue after causing damage to their wooden floor. We had been putting some cracks in the flooboards, but the straw that broke the camel's back came last Tuesday when someone smashed the end off one of the floorboards. The floorboard cracked about 20cm from the end where it butted onto another floorboard.
The venue was obviously unsuited to kendo, but is it really necessary to stamp that hard? My instructor tells me that you shouldn't really have to stamp so hard you break floorboards, and I tend to agree.
I was wondering whether anyone else out there has had any similar experiences.Whoa! That's some serious stampin'!
I never really focused on making loud noises with my foot. I know a strong stomp always seems like good technique, but people with big feet and stong legs can produce robust sounds without really getting the proper thrust movement correct.
In my opinion, this is the most difficult and most fundamental aspect of kendo. I go for a long lunge, reaching my right leg (not too high off the ground) close to my oponent's center. Always keeping your back perpendicular to the floor (no leaning, please), the stomp sound is generated by your body weight landing on your right foot.
For people like me who are not too heavy and with small feet, the stomp volume is quite wimpy. But this is better, I think, than making an effort to kick the planks up from the gym floor.

[Anime12478]

I never knew that people could stamp so hard. I hope that it doesn't happen with my Kendo club! The only venue that we have are the raquetball courts in the rec center on campus and we only have access to an air conditioned room at a community center not far from campus.

When I stamp, I just make the noises with proper technique instead of hitting my foot on the ground so hard. When you have the body-type I have (small, skinny), making sounds can be a problem. If you slam it on the ground, then that is just a recipie for pain in my book.

[nalogg]

Dude, that's crazy!

Well it must have been a shoddy floor to begin with, but just as you've said:
it's the straw that broke the camel's back.

If it had been used for kendo for a long time then it can surely break.

Everyday usage is rough on objects...
take for instance, there's this big famous statue of jesus who's MARBLE FEET have worn away just from hundreds of people a day touching them and praying.

and not rubbing them like a genie lamp, just touching them while they say a prayer.

but it's awesome that you guys broke the floor... i think that's HARDcore!

[Nanbanjin]

Thanks for the replies. It's nice to hear that elephant stomping isn't too widespread. The floor was probably too brittle for kendo too, so I'll be more careful the next time I have to find somewhere to train.

[not-I]

Ever check out the appendix on fumi-komi in Hiroshi Ozawa's Kendo: The Definitive Guide? To wit:

"...As shown in the table a shomen strike by a man generates an average force of 884.6 kgw in the vertically downward direction, 85 kgw in the backward direction, and 73.1 kgw in the right direction. In fact, some of those taking part in the experiment registered a force of over one tonne (!!!) in the vertically downward direction..."

In short, i don't think you guys were at fault. It was just a bad floor for kendo.

[Lloromannic]

Ever check out the appendix on fumi-komi in Hiroshi Ozawa's Kendo: The Definitive Guide? To wit:

"...As shown in the table a shomen strike by a man generates an average force of 884.6 kgw in the vertically downward direction, 85 kgw in the backward direction, and 73.1 kgw in the right direction. In fact, some of those taking part in the experiment registered a force of over one tonne (!!!) in the vertically downward direction..."
Is that for the combined forces of the actual shinai strike plus the fumikomi or just the fumikomi?

[Haowen]

Is that for the combined forces of the actual shinai strike plus the fumikomi or just the fumikomi?

It was a "special device". I believe it was some kind of sensor board on the floor, so those forces are what's on the right foot only.

[Kingofmyrrh]

that must have been quite a shock...
as pauly says, I don't think that deliberately trying to stomp hard when first learning fumikomi is particularly helpful. In fact, it's probably counterproductive as it might distract you from getting the correct movements down.
However, I'm sure you know this perfectly well without me telling you! For more advanced people, once correct fumikomi is 'mastered', then I think that stamping as hard as you can, while maintaining a relaxed foot and leg, is definitely a good thing. I've certainly been told so by senior instructors any number of times. For a start, big fumikomi seems to help with drawing the left foot up quickly and sharply, as well as adding definition to the actual strike. At least that's how I find it...
Unlucky about the floor though.

[indigo0086]

our dojo is messed up in some places. The tiles are about 2x6inches or so and some of them are raised, some are sunk and the laminate is all that's keeping it level. I think they are working on getting some repairs or a new type of floor.

[nodachi]

I find, of course I could be wrong, that proper, straight form and shifting of your body weight to the right foot produces strong fumikomi stamps. This is just from personal experience, but if I try to make a big stomp, it hurts the foot and results and a not good stomp. Focusing on shifting my weight onto the foot makes a nice stomp without trying to force a good sound.

Basically I am saying good form will give better fumikomi rather than actually trying to make a big sound. Of course, I could be wrong... <the basic disclaimer>

[Nanbanjin]

that must have been quite a shock...
as pauly says, I don't think that deliberately trying to stomp hard when first learning fumikomi is particularly helpful. In fact, it's probably counterproductive as it might distract you from getting the correct movements down.
However, I'm sure you know this perfectly well without me telling you! For more advanced people, once correct fumikomi is 'mastered', then I think that stamping as hard as you can, while maintaining a relaxed foot and leg, is definitely a good thing. I've certainly been told so by senior instructors any number of times. For a start, big fumikomi seems to help with drawing the left foot up quickly and sharply, as well as adding definition to the actual strike. At least that's how I find it...
Unlucky about the floor though.

I know that there is a lot of power generated in fumikomi, but I can't help feel that actually putting holes in the floor is a sign that your leg is too tense. I have never heard of anyone in Japan putting their foot throught the floor, and have never heard anyone say that cracking floorboards was a good idea. My understanding is that if you do it as you have described "while maintinaining a relaxed foot and leg", the force would be dissipated throught the entire sole of your foot and you would be less likely to cause damage to the floor. It was interesting that we didn't have much of a problem during Saturday class, which was mostly attended by senior grades. It was only after we started training on Tuesdays with more beginners that things started to fall apart.
I was open about it from the outset with the caretaker of the hall, but it's still pretty embarrassing.

[Kingofmyrrh]

I agree entirely. After spending a considerable time trying to get the correct timbre when I stamp, I now found that even if I use fumikomi footwork as hard as I can on a concrete floor, it doesn't actually hurt me at all. At worst, it might sting the sole of my foot a little, kind of like being slapped. I'm guessing that this means that the impact is being absorbed over the whole surface of my foot. Of course, I can hardly recommend doing this repeatedly...
You said that you'd never heard of it happening before in Japan, which actually reminded me of another of those kendo legends floating around. It basically involved some guy who got badly pasted or something, left for a bit of shugyo, then returned to the same dojo to rechallenge his former opponent. They were said to have stood facing off for nearly twenty minutes, until they both leapt for men. Our hero not only beat the other guy to the punch, he also stamped so hard that his foot went through the floor. It's said that they still keep the broken floorboard in commemoration of this duel. However, I don't know where this took place, and although I did hear names mentioned I don't remember them, and my best idea of the period is 'days of yore', so it's not exactly something to be quoted as absolute truth...

[Nanbanjin]

I agree entirely. After spending a considerable time trying to get the correct timbre when I stamp, I now found that even if I use fumikomi footwork as hard as I can on a concrete floor, it doesn't actually hurt me at all. At worst, it might sting the sole of my foot a little, kind of like being slapped. I'm guessing that this means that the impact is being absorbed over the whole surface of my foot. Of course, I can hardly recommend doing this repeatedly...
You said that you'd never heard of it happening before in Japan, which actually reminded me of another of those kendo legends floating around. It basically involved some guy who got badly pasted or something, left for a bit of shugyo, then returned to the same dojo to rechallenge his former opponent. They were said to have stood facing off for nearly twenty minutes, until they both leapt for men. Our hero not only beat the other guy to the punch, he also stamped so hard that his foot went through the floor. It's said that they still keep the broken floorboard in commemoration of this duel. However, I don't know where this took place, and although I did hear names mentioned I don't remember them, and my best idea of the period is 'days of yore', so it's not exactly something to be quoted as absolute truth...
I just hope the guy in the legend doesn't train where I have to front up to the caretaker afterwards.

I think the problem might be in pushing with the heel when landing. I think that when you land you are supposed to use the glute and the back of your leg as well as the muscles in the tanden. Some people want to smash down hard with the thigh muscle as the main power generator. Not only does this make it hard to focus power in the tanden, but it also forces the heel forward into the floor, which might break floorboards.
I'll have a look at the style of the guy who did the damage and see if it backs up my theory.

[nalogg]

In fact, some of those taking part in the experiment registered a force of over one tonne (!!!) in the vertically downward direction..."

notI, you're a cool guy and everything... not to disrespect you but...
Somehow i don't believe that one bit....
the person would have to weigh a lot and jump up quite a bit before the stomp to get that kind of force.. also the surface area of the balls of the feet couldn't stand an impact of 1 ton, the ligaments in the feet would tear, the heel would hit the floor and shatter bone.

er... does downward force refer to combined stomp AND strike?.. because if you're adding up a few elements i suppose the combined force could be a ton MAYBE (for a fairly big person) but it's still such a slim chance.

[Nanbanjin]

notI, you're a cool guy and everything... not to disrespect you but...
Somehow i don't believe that one bit....
the person would have to weigh a lot and jump up quite a bit before the stomp to get that kind of force.. also the surface area of the balls of the feet couldn't stand an impact of 1 ton, the ligaments in the feet would tear, the heel would hit the floor and shatter bone.

er... does downward force refer to combined stomp AND strike?.. because if you're adding up a few elements i suppose the combined force could be a ton MAYBE (for a fairly big person) but it's still such a slim chance.

To give Not-I credit, I have the book by Ozawa-Sensei that he is referring to so I can vouch for the validity of the quote.

[Curtis]

To give Not-I credit, I have the book by Ozawa-Sensei that he is referring to so I can vouch for the validity of the quote.This is a well know study that was done several years ago and is partially reprinted in Ozawa's book. I may even have the Kendo magazine it appeared in, in a box somewhere.

[nalogg]

To give Not-I credit, I have the book by Ozawa-Sensei that he is referring to so I can vouch for the validity of the quote.
that's crazy!
i just wonder what they're calculating

[not-I]

that's crazy!
Well, yes, it does sound pretty wild. But consider that the force is being applied to a relatively small space, which increases the actual kg. per square cm of pressure by a large degree.

There is a story of a duel between Shusaku Chiba and Matashichiro Takai where Chiba beat Takai with one tsuki, breaking through the floor in the process with his fumi-komi. Supposedly, the dojo owner cut out the flooring and framed it and there is a woodblock print form 1811 depicting the famous stomp. (As described in D.M.Craig's Heart of Kendo)

Anyway, here is some more on the fumi-komi study quoted in Kendo: The Definitive Guide. Unfortunately, Dr. Nagiri's apparatus is not described in detail.

"Fumi-komi-ashi is, understandably perhaps, notorious in the world of kendo. There are even tales of how at the moment of performing fumi-komi-ashi someone actually slammed their foot right through the floor. So just how much force is generated?

Dr. Fuminori Nagiri, a scientific consultant for the AJKF and a Professor of Tokyo University of Agriculture and Technology, used a special device to measure the force generated in three directions by the right foot at the moment of fumi-komi-ashi: forward and backward, left and right, and vertically downward. As shown in the table a shomen strike by a man generates an average force of 884.6 kgw in the vertically downward direction, 85 kgw in the backward direction, and 73.1 kgw in the right direction. In fact, some of those taking part in the experiment registered a force of over one tonne in the vertically downward direction. In the case of a kote strike too, quite a large measure is evident - an average of 769.5 kgw in the vertically downward direction. [...]

As these figures would indicate, failure to perform fumi-komi-ashi correctly will naturally increase the likelihood of sustaining a heel injury. If this is to be prevented, fumi-komi-ashi must be executed at virtually the same time as the strike, and the entire sole of the foot should come into contact with the floor."

Happy stomping! :wink:

[Haowen]

Well, yes, it does sound pretty wild. But consider that the force is being applied to a relatively small space, which increases the actual kg. per square cm of pressure by a large degree.

Not exactly. :)

The measurement was in kgw: kilogram-weight = Newtons, a unit of FORCE not pascals or bars, which is the unit for PRESSURE.

So this is the actual force that was applied. The area does not matter.

It is the same as if for a split second a 1-tonne anvil was sitting on the area of the sole of a foot, then it disappeared.

What makes it possible (to explain to Nalogg why a human being weighing under 100 kilograms can make a force of 1000 kilograms downwards and not fracture every bone in their foot) is that this is instantaneous force, not sustained force. It is a tremendous amount of force applied for a very very short time. The kendoka's leg only has to be able to absorb the maximum force for an instant, not support it for any amount of time. I'm no expert but I think the elastic properties of materials are very different for such instantaneous stresses (e.g. water is like a brick wall if you slam into it at high velocity, because it has no time to "give").

[not-I]

I'm no expert.
I wouldn't know a physics expert from a hole in the ground, but your post seemed pretty solid. I was wondering what kgw was all about. Thanks for explaining.:happy: