OK, maybe my last post didnt deserve response.
Chi Kung_ In the variety of chi kung w/ Master Huang I have not encountered holding the breath unless one counts either the obligatory exaggerated swallowing of saliva collected during practice (tip of tongue to palate) or the momentary hold at peak inspiration and expiration during preparation for chi kung (and same prep prior to Ba Gua) where visualization of movement of energy is raising and lowering through energy channels and looking within for imbalances(Inhale palms rise up,exhale as palms face down,inhale and expand, exhale and compress)...otherwise breathing was to be in through nostrils out through mouth, and even with a static pose like (Love these names) "Monkey awaits Peach" or end of lion chi kung ("lion shakes his mane") where the simple direction to keep hands in lion claw tight and "just relax and shake" if you dont breath like a bellows you wont last to the next.
Yoga_ Yoga Pranayama practice begins without breath hold, as student learns to move energy through the energy channels in the spine and using nostril closing balance the Ida and Pingale (Yn/and yang) channels of spine (a familiar autonomic function one has probably already noticed, the cycle of one nostril dominant (more open) the other passive less open or even clogged. Breath holding is practiced w/ energy locks (Physical restrictions on primary areas of body where energy is lost) to build internal energy in preparation to awaken kundalini shakti and begin to raise to the crown chakra, Not unlike chi kung and the jade nectar mentioned above. Yoginda back to time immemorial have cautioned the unwary (read, no teacher, not ready, not practicing ridding excess energy after practice, abusing the accumulated energy) that headaches, illness, insanity and even death are possible.
Buddhism_ Other than development of internal energy, control of the breath is the first control of a generally autonomic function, control of the breath requires focus, focus is required for meditation and the transformation of the Mind. This part is outrageous, His Holiness the Dalai Lama has written that meditation can begin when one can focus "vividly and continuously for Four hours,stability can be said to be achieved" paraphrase from "How to Practice" HH the 14th Dalai Lama pg127, there is no mention of breath holding.
do not try to spork the post, for that is impossible, only realize there is no post to spork