Hi Lungyuil,
Apart from structural integrity, the vertical fist tends to keep the elbow from deviating from its intended trajectory. i.e. In karate the twist is supposed to come very late in the punch, but I have seen many people turn early in which case the elbow drifts out. This decreases the ability to transfer the full force of the blow.
However I do think the main reason for punching like this to maximise risk strength.
Some of you are confusing use of the verticle fist with the question about the lower knuckles. Two seperate subjects.
[i]Signed,
Rogue, Soke and Senior Grandmaster of Southeast American Brazillian Bagua Combat Chi jitsu Kempo Karate Do and Choral Society.
The only tactical principle which is not subject to change; it is, “To use the means at hand to inflict the maximum amount of wounds, death, and destruction on the enemy in the minimum amount of time." [/i]
Wcfish
I agree with the concept of having the elbow facing the ground. when we punch our elbow always faces the ground and our fists are never horizontal. They are almost at a 45deg angle. The punch is more natural, the elbow never locks out.
This increases the power and helps the six powers (luk ging).
<BLOCKQUOTE><font size=“-1”>quote:</font><HR>Originally posted by rogue:
It’s not just the fingers being damaged that you need to worry about. Stability of the wrist can also be a factor.
The reason that the bottom of the hand is less stable is that’s where it flexes from. Note the palmaris longus, the flexor carpi ulnaris and the flexor carpi radialis.
While you can punch with the lower three you need to be aware of a few more things that can go wrong, like your wrist buckling in.
." _[/quote]
It doesn’t follow that because the wrist flexes at the bottom that punching with the bottom knuckles is less stable.
The important thing is the alignment of the arm/wrist/hand. In most instances using a vertical fist requires you to punch with the bottom 3 if you want to keep correct alignment.
If you are impacting with the top 2 then you are punching with a bent wrist.
P,
The instability is in the hand flexing in, not up or down.
[i]Signed,
Rogue, Soke and Senior Grandmaster of Southeast American Brazillian Bagua Combat Chi jitsu Kempo Karate Do and Choral Society.
The only tactical principle which is not subject to change; it is, “To use the means at hand to inflict the maximum amount of wounds, death, and destruction on the enemy in the minimum amount of time." [/i]
<BLOCKQUOTE><font size=“-1”>quote:</font><HR>Originally posted by rogue:
P,
The instability is in the hand flexing in, not up or down.
_Signed,
" _[/quote]
Whatever - I don’t think you establish this is the case - you make a claim which your reasoning does not support.
I can see that if you punch with the top two that you are going to risk the fist flexing downwards - especially if you are hitting with a slightly upwards trajectory - because the wrist is going to have to be bent on impact.
I think Rogue should define “flex” for us, how about it Rogue. Please include, definitions of extension, abduction, adduction, supination and pronation…of the rist of course.
Thanks.
The wrist will turn if a) you flex and cause it to turn or b) the force from impact is not transmitted directly and lineaerly to the forearm.
The wrist has range of motion in many directions and each direction is a possible danger when punching. If alignment is correct then none of the force is against the wrist and its musculature. Wrist stability is NOT dependent upon fist orientation. The horizontal fist is just as vulnerable to flexion in the up and down direction as the vertical fist is in the in and out direction.
Horizontal fist/first 2 knuckles are and vertical fist/bottom 3 knuckles are used with different mechanics to accomplish different things. Both work within the framework that they were designed for. You cannot simply substitute one for the other arbitrarily without understanding everything else in the martial art system.
Dzu
‘I think Rogue should define “flex” for us, how about it Rogue. Please include, definitions of extension, abduction, adduction, supination and pronation…of the rist of course.
Thanks.’
Once you master small words, then we can move onto the bigger ones. 
[i]Signed,
Rogue, Soke and Senior Grandmaster of Southeast American Brazillian Bagua Combat Chi jitsu Kempo Karate Do and Choral Society.
The only tactical principle which is not subject to change; it is, “To use the means at hand to inflict the maximum amount of wounds, death, and destruction on the enemy in the minimum amount of time." [/i]
Typoes aside, how about defining the above mentioned for us. 