for those who didn't know about it...my research was in the form of a survey of 101 dojo, purely gathering info, a snapshot if you will. The link follows...the 2 most interesting things to me were that a small handful of dojos were responsible for a large proportion of the acute knee injuries and that despite many complaints - including MINE - over the yrs about feet sticking to soft mats, there didn't seem to be a correlation btwn wrestling type mats and acute knee injuries.
I have read your article and the 2004 follow-up and think it would be very good to have much more research done on the correlation between mat type and knee injuries.
Apart from the very earliest dojo (at Sussex University in the late 60s / early 70s, if anyone can remember that far back), the mats at pretty well every dojo I myself trained in were traditional Japanese straw tatami, like the ones I have here in my living room (I am not sure about Tenpukan, near Earls Court in the UK, during the mid-70s). Usually they were covered with canvas, but the few knee inujuries that occurred usually came from collisions due to careless ukemi, rather than from twisting the knee joints from taisabaki. The tatami were always very hard and I was always taught that this was best for the knees, though rather painful for the rest of the body until one became accustomed to them. All my teachers were Japanese and 30 minutes of suwari-waza was about the norm for each class.
In Japan, especially in Hiroshima, every dojo where I have ever trained has traditional tatami and I think you need to live here to see how 'normal' this is. For example, every night I roll out my futon in my wooden house and sleep on the tatami. (The floors are sprung and there is a sizable gap between the floor and the ground. The tatami in the bedroom were replaced a few years ago, at a cost of 10,000 yen each. The ones in the living room are becoming faded from the sunlight and so will need to be re-covered in the near future. A craftsman from a local tatami shop will come and do it while I am away.)
When I receive visitors, it is all done in seiza, with zabuton
(cushions) available for those who need them. In my experience of 28 years in Japan, no Japanese has ever accepted a cushion when I have remained sitting in seiza on the bare tatami. Perhaps it is a matter of national pride...
The point I am making here is that certain traditional Japanese arts, including budo, and wooden floors covered with tatami go together like two sides of the same coin. I remember my first visit to the Itsukushima Shrine (which is the famous shrine illustrated in all the guidebooks, which you see when arriving in Miyajima by ferry). I watched a series of Noh plays performed on the ancient Noh stage. I had no clue about the plays, but I was struck, forcibly struck, by the elderly ladies who sat in seiza hour after hour and followed the texts in their books. I had been practising aikido for just over 10 years, was a yudansha, and thought I could do seiza and suwariwaza pretty fast and efficiently. But continuous seiza for three hours...? Actually, these ladies sat in a kind of semi-seiza, where the legs were sometimes tucked under the lower body and they shifted their weight from time to time: something you should NEVER do in aikido training sessions when the sensei wants to give a long lecture about the real meaning of aikido...
My own knee injuries were not incurred from the quality of the tatami, but the elderly surgeon who did the operations on the meniscus once told me that I would suffer from arthritis as I got older, and so it has proved. He thought the physiotherapy regime had been far too severe to give the joints time to recover from the operation.
Because of my position in the IAF, I travel abroad fairly regularly and on these occasions also give training courses. After a recent yudansha workshop (the relevant part of which was devoted to a practical application of the principles of aikido randori: see George Ledyard's work on this), my right knee was very heavily swollen and I could not bend it very far. The workshop had been held in a dojo with very soft mats (not wrestling mats), which look like traditional tatami, but are not. And the floor was not sprung.
I am undecided about the quality of these mats, but I can speak from immediate experience when I state that I always have to spend more time recovering from knee strain after giving courses on mats such as these, than I have done from intensive training on traditional Japanese tatami.
However, there are loads of variables here. The training courses I give are fairly intensive, with practice around 4 - 5 hours daily for a continuous period of up to one week. This is somewhat different from the average. So, it would be very good if you did a wider survey relating to training conditions, type of tatami. The USA would be a very good place for such a survey, since there are many Japanese shihans who were brought up in the traditioinal way and so might have opinions on the quality of the tatami in their own dojos.
Now I have found a good doctor of kanpo-yaku and I am following the example of the late Kanai Sensei, with lots of moxibustion, acupuncture on my knees and very severe massage on the rest of my body.
In terms of my awareness of my own body, my knees are back to the state they were in before the intensive workshop training, but I do not know whether this is due to the kanpo-yaku treatment, or to the absence of such intensive training.
EDIT: So. I think the general conclusions of Gaku Homma in his article are correct. However, as someone who teaches comparative culture, I want to stress the grave dangers of making generalizations about the knees of a particular culture: e.g., 'Japanese' knees are more adapted to suwari-waza than 'western' knees. All knees outside Japan follow a particular pattern of some undetermined kind. Which is why Janets's research is so important.