Breathing with different temporal correlations is called Visama Vritti Pranayama, which has numerous variations of the correlation and is widely used in the practice of Yoga.
4. Breath Delays
The breath may be delayed after the inhalation (T1) and after exhalation (T2). According to the temporal correlation, they may be equal (T1 = T2) or different. Delays after the exhalation are longer than after the inhalation (T1 < T2), or the delays after the inhalation are longer than after the exhalation (T1 > T2) (Fig. 33).
Breathing with delays is called Ujayi Pranayama; it is also widely used in Yoga practice, and has a number of variations differing in the presence of stops and the temporal correlation of the delays after the inhalations and after the exhalations.
Breathing delays may also be performed, not only after inhalation or exhalation, but also during the inhalation (T1) or during the exhalation (T2) — in the form of «steps» (Fig. 34). This type of the breathing is called Viloma Pranayama.
5. Depth of Breath
Breathing depth (amplitude) may change independently, towards the increase of the inhalation (V2 --> max), or of the exhalation (V1 --> max); or towards the decrease of the inhalation (V2 --> min) or of the exhalation (V1 ® min). Simultaneously, it can change towards the increase of the inhalation and the exhalation ((V1 + V2) --> max), and towards the decrease of the inhalation and the exhalation (V1 + V2) --> min) (Fig. 35). In this event, the scope of variation towards the inhalation and towards the exhalation may be equal or may vary.
Depth of breathing increases during the performance of different Pranayamas, requiring increased time of the inhalation and/or the exhalation, during special hyperventilating exercises facilitating fast restoration and increase of the energy potential, or during intensive physical exercises comprising the training requiring more energy resources. The depth decreases upon the transition from intensive lung ventilation modes back to «normal» breath, or during deep physical and psychic slowdown during the «dive» in relaxation.
6. Breath Frequency
The frequency of a breath may vary towards an increase or decrease in the number of breath cycles for a particular time unit. This is achieved by the acceleration or slowdown of the inhalation time (T1 > T3) or the exhalation time (T2 > T4), as well as by the acceleration or slowdown of both times simultaneously ((T1 + T2) > (T3 + T4) or (T1 + T2) < (T3 + T4)) (Fig. 36). The rate of acceleration or slowdown of inhalation and exhalation may be equal or may vary.
Breath frequency is increased during the practice of Bhastrika and Kapalabhati Pranayamas, as well as other hyperventilating breathing exercises, and is reduced upon the change of hyperventilation to «normal» breath, or during deep relaxation when there is a slowdown of the rhythm of breath.