Verse 1.3.5

अतो यान्यन्यानि वीर्यवन्ति कर्माणि यथाग्नेर्मन्थनमाजेः सरणं दृढस्य धनुष आयमनमप्राणन्ननपानंस्तानि करोत्येतस्य हेतोर्व्यानमेवोद्गीथमुपासीत ॥ १.३.५ ॥

ato yānyanyāni vīryavanti karmāṇi yathāgnermanthanamājeḥ saraṇaṃ dṛḍhasya dhanuṣa āyamanamaprāṇannanapānaṃstāni karotyetasya hetorvyānamevodgīthamupāsīta || 1.3.5 ||

5. This is why, while doing feats demanding great strength—such as producing a fire by rubbing one stick of wood against another, running up to a target, or bending a stiff bow—a person does not breathe in or breathe out. For this reason, one should worship this holding of breath, called vyāna, as udgītha [Om].

Word-for-word explanation:

Ataḥ, this is why; yāni, those; anyāni, other; vīryavanti, demanding great strength; karmāṇi, feats; yathā, such as; agneḥ manthanam, igniting a fire by rubbing one piece of wood against another; ājeh, a target; saraṇam, running up to; dṛḍhasya dhanuṣaḥ āyamanam, bending a stiff bow; aprāṇan anapānan, without breathing in or breathing out; tāni, all those [feats]; karoti, one accomplishes; etasya hetoḥ, for this reason; vyānam eva, vyāna; udgītham, as udgītha [Om]; upāsīta, one should worship.

Commentary:

Whenever you do something that demands much application of strength, you must resort to vyāna. Take, for instance, deeds such as producing fire by grinding one piece of wood against another, or running up to a target, or bending a stiff bow. In doing each of these feats, you have to hold your breath. Even when you speak, you hold your breath. This distinguishes vyāna from other forms of breathing. Vyāna, therefore, deserves special worship, for vyāna is in a class by itself. It gives you strength.