Why does the fist travel up the outside of the body?

In Isshinryu, my system of practice as example, the vertical punch stays aligned with the outside of the body (see snapshot). When executed in the basics and the kata, most executions, the fist seems to move, rise up, toward the outside of the bodies of both the person executing it and the adversary as they stand facing, i.e. during two-person drills. Granted, this may not be the intended targeting yet when you watch video’s or actual demonstrations this is where you see punches go as to paths. 

Take a look at the top view I attempted to draw as to the pathway of a vertical rising punch seen in basics as kata.

The question comes up rarely because when taught the practitioner, being a novice and even student, tends to blindly accept that this punch is done this way because ….

In my view this is inadequate and missed a very important lesson taught through both basics and drills. Much of bunkai is molded to fit certain applications rather than reality. Yes, the rising punch when applied in appropriate situations for appropriate actions is a good thing. It is not the end all thing as often assumed in training and practice. It is about how to use a basic, fundamental concept, to achieve a better, reality based, application once you pass the basic/novice teaching and learning levels.

Explain dude, this is confusing you might ask, well it is about taking the more educationally modeled basic applications and moving them toward a more realistic practice. Here is what I am aiming at:

The rising punch as depicted in the snapshot of Tatsuo-san, although not a basic or kata based other than in this pose for sanchin [couldn’t find or create an adequate and accurate rendition], simply demonstrates the proper, fundamental, way to perform the punch with not further explanation as to how that punch is actually applied. This is due to the educational modifications of kata, etc. for the educational systems implemented early 1900’s and not reverted for more progressive practice and training. 

In reality, the pathway of the punch, if done with proper kamae, results in the person applying the punch moving off-center of the adversary so that the punch is actually applied to the centerline of the adversary. This is the simplest bunkai for this post. See second snapshot below.

One of the major bunkai that is not readily present or observable for both basics and kata are the shifts necessary to move off center of an adversary while maintaining our centerline to achieve an application of a technique like this one, i.e. to achieve maximum efficiency and application while providing a type of Loop (OODA) reset to the adversary, etc. 

To apply this technique and follow the principles the practitioner must move off the adversary’s centerline and often at about a twenty degree offset to the right and forward (not depicted in snapshot) as the rising punch is redirected toward the adversary’s centerline, i.e. the solar plexus, while the shift and turn of the body keeps the practitioner’s centerline toward the adversary’s centerline while taking the adversary’s centerline off causing a reset of the, observe and orient, loop thus providing time for the practitioner, etc. 

If you view the makiwara basics below you will notice that when punching the makiwara the practitioner has their body shifted to one side and the other for proper punch application in relation to the practitioners body as the makiwara represents the centerline of an adversary and so on. 

This is to depict the positioning of the vertical rising punch as executed in basics and kata drills, etc.

When normally practiced, the fist path is directly forward as if the punch is going to hit a target of the adversary's shoulder/arm vs. the centerline solar plexus.

In this version, the practitioner shifts to the left so that the punch will strike the adversary's centerline/solar plexus, as only one possible target, taking their centerline away from the adversary while maintaing the integrity of the punch, body, alignment, etc., to achieve greater power to the target, etc. Keeping to the fundamental principles and exploiting the adversary's OODA, i.e. reset the loop to OO levels to gain and maintain the advantage and so on ….

Addendum dtd December 15th, 2015 at 9:59hrs:

Take a look at the Makiwara video at about 5:19 minutes to see the shifting movement I mention in this article:

https://www.youtube.com/watch?v=KyF7OsPlPKE

Then take a look at a video made by Andy Sloane Sensei, Go-dan Isshinryu as well as Isshinryu Historian:

https://www.facebook.com/video.php?v=10203816053625960&set=vb.1358361539&type=2&theater

If you cannot see the above from Sloane Sensei take a look at his FB Wall to find it:

https://www.facebook.com/andy.sloane.79?fref=browse_search

Remember, all bottles are good, they all serve a purpose.