I understand that the spinal breathing pranayama is movement of awareness up the spine with an inhale and down with an exhale.
The standard meditation practice is mental repetition of “I am”.
How viable is just moving awareness up and down the spine as the meditation object? Its something I like doing when I’m sleeping at night, I can do more “reps” of this per unit time if I don’t do it in conjunction with the breath, and its kinda relaxing, but how does this differ in the effects from the spinal breathing pranayama?
So, essentially, the practice of Spinal Breathing Pranayama does require the movement of the attention to be synchronised with the breath, going up on the inhalation and down with the exhalation. Of course, the practice could be done without this, but something important would be lost. Moving the attention in the body, causes prana to flow in the body, and the flow of prana follows the attention. But the breath also causes prana to flow in the body, with prana flowing up the body on inhalation and down the body with every exhalation.
So, by combining the movement of the attention with the movement of the breath, we are bringing both of these flows of prana into sync. And when these flows of prana are brought into sync, this has a powerful purificatory effect on the subtle nervous system. And if the breath is slowed down, and deepened at the same time, this will also increase the strength of the inner purification that is happening.
Of course, outside of practices, you are free to experiment with anything you want to. But this would be your own experiment and we would not be able to predict the long-term results. See this lesson for more on researching modifications to practice:
Personally I do not recommend experimenting with modifications to practices unless you are very stable and have a very clear sense of the flows of prana in the body. Even then, I would suggest proceeding with caution. The subtle nervous system, and the human body, are quite delicate and easily thrown off balance.