Qigong involves breathing but it is not its raison d'etre........
..... I am unaware of any scientific studies done to prove or disprove these stated benefits, but it definitely does have beneficial effects that one can feel. The existence of 'meridians' is something western science is skeptical on.
Yours in Taiji,
IMMHO Regardless to the existence of 'meridians' is something western science is skeptical on. It is true that there isn't any scientific studies done to prove or disprove these stated benefits. However, if breathing was not done in those practices mentioned above, I can assure you that none of the beneficial effects can be achieved.
The so-called meridians can be found in the physiological diagrams. If one look close enough, each meridian is corresponding to a nerve in the human nervous system. For instance, the Heart Meridian is actually lies on the Ulnar Nerve. When a needle was placed on an acupuncture point of the Heart Meridian, actually, the Ulnar Nerve was being stimulated. Of course, this would lead to another discussion.
A deep discussion requires explicit details for a good comprehension of a complex subject.