[Prāṇāyāma has] external, internal, and retention movements, regulated by place, time, and number, becoming long and subtle.

This sutra details the modalities of prāṇāyāma:

Bāhya: external movement, exhalation. Ābhyantara: internal movement, inhalation. Stambha: retention, suspension of breath.

These are regulated by: Deśa: place, where attention or prāṇa is directed. Kāla: time, the duration of each phase. Saṃkhyā: number, the repetitions or proportions.

Paridṛṣṭa means “observed” or “regulated” according to these parameters.

The result is that breathing becomes dīrgha (long) and sūkṣma (subtle). What began as ordinary breathing transforms into barely perceptible movements of refined energy.