Here I am choosing not to focus on the Pūrvāṅga, the ascending or preparatory phase, nor on the Uttarāṅga, the descending or compensatory phase of the Āsana used in the Vinyāsa Krama for the whole practice.
It also does not include the building in of additional techniques such as Prāṇāyāma, nor exploring the different roles Prāṇāyāma may have in relation to the whole practice, especially one that has incorporated additional techniques such as the Catur Bandha.
Instead this extract is an example of the Pradhānāṅga or crown of this particular practice. It is centered around a stay in Mahāmudrā of around 10 minutes each side progressively incorporating and building in intensity, within the Vinyāsa Krama for Mahāmudrā, with the additional techniques of the Catur Bandha.
Each step of the Vinyāsa will intensify with the building in of an additional Bandha and also in one of the steps, the intensifying of the breath length and ratio. This example is as taught to me by Desikachar within my 121 lessons, at this particular juncture around the application or Viniyoga of the Catur Bandha, all from the teachings of Krishnamacharya.
This particular practice example is obviously for an advanced Āsana student who is not only familiar with the concept of the Catur Bandha, but has also the prerequisite of a working competence with combining all four Bandha into one Āsana, whether it is used as a base for Mudrā practice or for Prāṇāyāma practice.
Mūla Bandha is that part of Uḍḍīyāna Bandha that you do not release.
This working competence with the Catur Bandha also implies a prior training and working competence in a variety of breathing ratios in Āsana and in Prāṇāyāma, especially ratios which utilise the Bahya Kumbhaka.
There are three steps of four breaths for each stage of the Vinyāsa and the same three steps are repeated when staying on the second side. The core ratios used are 126.96.36.199 and 188.8.131.52 with a breath length of between 42 and 48 seconds.