The term Seichujiku is commonly used when talking about using Seichusen for axis spinning. Seichujiku is therefore a part of Seichusen. It is an aspect of it. A stable axis creates speed and smooth movement and having one is considered a quality.
The Kanji used for Seichujiku are almost identical to Seichusen, with the exception of the last Kanji. Jiku translates into axis, pivot or stem although the first and second one should be considered, terminology wise. When talking about Seichujiku, there are one axis and two axes movements.
Although the methods listed below contain more than just rotation - they are excellent to focus on Seichujiku development.
Forward movement and to the side only help you so much as these are directions we naturally move in. We're used to it.
With Ushiro Gyakuzuki you get the chance to explore uncharted territory that will develop your backward movement overall.