Also in the approach of Krishnamacharya and Desikachar to Yoga practice this idea is even more relevant as important information, that guides our initial and subsequent steps into Prāṇāyāma, is gleaned from certain factors only apparent from observation of how our respiratory system performs during Āsana practice.
Of course this presumes that the students Āsana practice faithfully follows and intimately integrates the many principles that Krishnamacharya taught to Desikachar around how and why we use, develop and progress the breath within Āsana.
Thus in this approach to the practice of Āsana and Prāṇāyāma all the information, such as the selection of breath length, breath ratios and thus choices that shape the direction for Prāṇāyāma, is gleaned from observation of the practice of Āsana.
In fact all the information necessary for integrating Prāṇāyāma into our practice Sādhana arises from observing the breath in Āsana, except one thing. We cannot easily observe the ebb and flow of the breath within an individual nostril within Āsana.
So to recap, in the approach of Krishnamacharya and Desikachar all the aspects of the students unique and individual relationship with the breath, except one, can be observed from what happens to the breath within their Āsana and Mudrā practice.
In reality all of this makes the teachers initial and developmental choices for Prāṇāyāma for the student more straightforward and systematic.
“Haṭha Yoga is Prāṇāyāma.”
– Śrī T Krishnamacharya
This information also guides the teacher in how to integrate this relatively obscure practice, in all but name, so that it evolves into the powerful tool Krishnamacharya proclaimed it to be.