Itosu's Heian (Pinan) katas were first performed in public around 1905. It seems apparent that he didn't share the applications of the katas with any of his students, leaving us a gigantic puzzle to unravel.
By 1920 (or so), Itosu's senior students were in Japan establishing various karate "styles." They taught the Heians to their students, and the Japanese, true to their nature, froze the katas as immutable lessons from the masters. With small exceptions, the Heian/Pinan katas have remained unchanged to the present day.
How, then, do we account for the fact that each style has its own, wildly different, set of Heians? In addition, each style has a different set of applications to demonstrate for each kata. The answer is that Okinawan karate masters expected their students to change and adapt the katas, and they did. In the fifteen years between their introduction and their fossilization, the katas changed remarkably down multiple independent paths.
This gives us an interesting opportunity. When we attempt to match applications to katas, we can view the katas in other styles to see whether this move appears everywhere, or is only in Shotokan. Sometimes the katas of other styles lend context to our part of the puzzle. It is always worthwhile to look.
Comparing Shotokan's H. Shodan to its counterparts in other styles, we note immediately that the embusen (floor plan) of the kata is different. Some styles use Shotokan's H-shaped pattern ( |---| ). Others use Itosu's original embusen, which looks more like a double-headed arrow ( <---> ). The "wings" of the kata used to be performed at an angle. This could have implications for applications.
There is a sharp distinction between Shotokan and non-Shotokan styles in step 1 of H. shodan. Instead of a front stance and downblock in step 1, the non-Shotokan styles do a hammerfist at shoulder level. They either pivot in place in cat stance, or they shift backwards into cat stance on step 1! These styles do a vertical hammerfist:
This style does a horizontal hammerfist in step 1:
These groups perform step 1 as a downblock in front stance:
- Wado Ryu
- Ertl and Bendickson (Shotokan)
- Sugiyama's group (Shotokan)
- Gichin Funakoshi's students, films from 1924 (Shotokan)
- Egami's group (Shotokai)
- Kenneth Funakoshi's group (Shotokan)
- Kanazawa's group (Shotokan)
- Nakayama's JKA (Shotokan)
- Modern JKA (Shotokan)
- Yamazaki's Robukai
The opening downblock seems to be "Shotokan only." (Wado and Robukai got their heians from Shotokan.) If so, then the hammerfist is the original technique.
In Step 4 of the kata we pull back, swing our fist in a circle, and then attack with a hammerfist. All branches of karate begin this sequence in a front stance and downblock posture, and then pull back to a semi-upright stance. Some branches remain in the upright stance while executing the hammerfist; other branches give power to the hammerfist by dropping into front stance again.
Upright hammerfist:
- Gichin Funakoshi's students, films from 1924 (Shotokan)
- Egami's group (Shotokai)
- Kanazawa's group (Shotokan)
- McGuiness's Seito Shito-Ryu
- Tomiyama's Tani-ha Shito-Ryu
- Nagamine's Matsubayashi Shorin Ryu
- Yamazaki's Robukai
- Wado Ryu
Dropping hammerfist:
- Ertl and Bendickson (Shotokan)
- Kenneth Funakoshi's group (Shotokan)
- Nakayama's JKA (Shotokan)
- Modern JKA (Shotokan)
- Sugiyama's group (Shotokan)
I would say that dropping down into front stance to augment the hammerfist is a mutation added to Shotokan after 1924. Non-Shotokans don't do this move, and early Shotokans didn't, either.
Step 6 is the left downblock followed by an open-handed upblock with the same hand. All Shotokan groups that I have seen perform the upblock completely before beginning to step forward for the next move.
- Sugiyama's group (Shotokan)
- Ertl and Bendickson (Shotokan)
- Nakayama's JKA (Shotokan)
- Modern JKA (Shotokan)
- Gichin Funakoshi's students, films from 1924 (Shotokan)
- Kenneth Funakoshi's group (Shotokan)
- Kanazawa's group (Shotokan)
- Yamazaki's Robukai
Non-Shotokan groups either skip the open-handed upblock completely, or perform it as a fleeting stackup before the upblock in step 7:
- Otsuka's Wado Ryu
- Nagamine's Matsubayashi Shorin Ryu
- Gillespie's Seito Shorin Ryu.
- McGuiness's Seito Shito-Ryu
- Tomiyama's Tani-ha Shito-Ryu
Another place where the katas differ is in the three upblocks (step 7-9). Some Shotokan groups do normal beginner upblocks here (fist closed). Other groups do an upblock and then open the hand into shuto position at the top of the block before stepping forward. I learned it with the shuto; was firmly admonished never to do shutos; and was then excoriated for failing to do shutos. None of the masters in question could explain why to do it or why not to do it. This is one of the places where Shotokan masters are a little bit insane.
Branches that do the shuto at the top of the block:
- Gichin Funakoshi's students, films from 1924 (Shotokan)
- Kenneth Funakoshi's group (Shotokan)
- Kanazawa's group (Shotokan)
- Nakayama's JKA (Shotokan)
- Modern JKA (Shotokan)
- Yamazaki's Robukai
Branches that omit the shuto at the top of the block:
- Sugiyama's group (Shotokan)
- Ertl and Bendickson (Shotokan)
- Nagamine's Matsubayashi Shorin Ryu
- McGuiness's Seito Shito-Ryu
- Tomiyama's Tani-ha Shito-Ryu
- Wado Ryu
And a surprise! The Shotokai branch does shuto upblocks and never make a fist during the upblocks:
Some styles do deep front stances for downblocks, but then use stiff-legged upright stances for the following front punches.
Upright front punches:
Deeply-extended front punches:
- Ertl and Bendickson (Shotokan)
- Sugiyama's group (Shotokan)
- Gichin Funakoshi's students, films from 1924 (Shotokan)
- Egami's group (Shotokai)
- Kenneth Funakoshi's group (Shotokan)
- Kanazawa's group (Shotokan)
- Nakayama's JKA (Shotokan)
- Modern JKA (Shotokan)
- Yamazaki's Robukai
Some groups do middle-level knife-hand blocks at the end of the kata. Others do knife-hand downblocks instead.
Knife-hand downblocks:
Mid-level knife-hand blocks:
- Ertl and Bendickson (Shotokan)
- Sugiyama's group (Shotokan)
- Gichin Funakoshi's students, films from 1924 (Shotokan)
- Egami's group (Shotokai)
- Kenneth Funakoshi's group (Shotokan)
- Kanazawa's group (Shotokan)
- Nakayama's JKA (Shotokan)
- Modern JKA (Shotokan)
- Yamazaki's Robukai
Even with these discrepancies noted, it is largely the same kata everywhere it is practiced. Downblocks; front punches; upblocks; knife-hand strikes. The differences are consistent with the philosophies of the founding masters of the different systems.