It doesn't appear to me, watching the many Shioda demos on YouTube, that Shioda sacrifices his ground connection when he is making serious contact with his uke. If you watch the clips, I think you will find that when he's doing his "Shioda Bounce"(TM) and is off the ground while his uke is also not grounded, he is just "helping" uke to complete an arc uke is already circumscribing in the air -- having already been off-balanced. Also, do not discount the very strong possibility that, besides the generous serving of "ham" Shioda often dished out in his public demos, his demonstration ukes did not always wait for Shioda to touch them before taking ukemi for that kind of schtick.
Whenever Shioda is actually applying aiki, he is in contact with the ground with at least one foot or his uke is in contact with the ground and Shioda is connecting to the ground through uke. As far as I can see, when Shioda is bouncing uke off his shoulder or hip -- doing aiki-age and aiki-sage, he is in solid contact with the ground.
Pushing into/engaging with the ground is an initiating step for generating force -- one of the precursors to transforming force into power at the tandan/meimon. Shioda's "sinking of the big toe into the ground" (really, pressing against the ground and gripping with the toes to exploit gravity force and to create torsion), is an example of that starting point for the force-generation process.
Being "rooted" doesn't mean being glued to the ground; mobility is essential to good martial-aikido movement. Someone with a reasonable degree of skill can exploit even just a quick "ground grab" to gain the necessary force for power generation, before moving on. I'd wager that whenever Shioda came to rest -- however briefly -- at any point between stepping and/or propelling himself around, he regained his root to initiate transmission of force.
Plenty of skips and hops here, plus a two-footed leaping slam-dunk:
(BTW, this clip has the classic segment of US Sen. Robert Kennedy and his wife enjoying a private demo with Shioda, with one of the senator's Secret Service bodyguards cheerfully getting himself face-planted.)
True, and you must have a lot of experience with internal stuff. If not in aikido itself, all the way able to translate it into the workings of aikido.
As I see it, and I think it shows in the video you provided, Shioda, in his younger life was still building on his reputation and whence probably more concerned with throwing his partners effectively. And whence, to my eyes, he is working more “one-directionally”. In his later years, there are videos where he is seen teaching, trying to impart the inner workings of his art to his disciples. Then, as I see it, he has more become like Ueshiba Morihei, who was more circum- or omni directional in his awareness, less concerned with throwing and rather concentrated inside himself, holding back, attracting, knowing that throwing was one choice of many things he could choose. In a sense more aiki than kiai.
Now, lets make an attempt to take this a little bit further: before I start training I have to set a goal. Lets first set a goal for ones training.
With internal training for aikido I like to think in metaphors or pictures. The extreme distinction between internal and external has always failed me.
When saying “one-directionally” I think of a picture like “bow and arrow”. External part in this would be, that you can make a stronger bow (you can train your body to get stronger) and can draw the arrow farther and direct it on a certain goal (store more trigger-energy and get your partner always in front of the arrow, or if you like in front of your sword, i.e. of your strongest point). I call it “external” because it can be seen relatively easily. It’s more kiai in that you do something with your partner.
Now, for more internal or more aiki, I tend to think of a modern jetfighter, that relies heavily on its inherent instability, to be able to react or act much faster than would be possible otherwise. To become stable, it has to take advantage of kind of dynamically omni-directional loss of balance. It’s more about what you do with yourself than what you do to someone else. Here, you want to take into account awareness of the ground, you have to know where and how you are situated in relation to the rest of the world.
To combine both aspects and to take more into account a living being, I come to think e.g. of a cat, completely relaxed, sleeping on a table, getting swept of the table by someone, who doesn’t want it to be there. The cat in the fall, her body immediately, in a flash, by its always present awareness of the ground, revolves, draws and triggers from the centre and lands on her feet, again relaxed and ready for what may happen next.
The next thing would be a cat like this, that can’t be swept off the table because no one can find it.
Kept carried away a bit.
To my mind, for internal training in aikido, one has to train the body, starting with a set goal, with the intention to ingrain the body with relaxed strength and constant awareness (which includes awareness of the ground) and the ability to take dynamic advantage of ones inherent instable human body.