These are expressions of "peng" that direct the body upward and downward, respectively. Besides requiring the use of internal body structure, the tanden/dantien and meimon/mingmen play a large part in creating this power effect. The shoulders, arms, wrists and hands are conduits for directing the force to the point of contact with uke, so there is relevance to the "shapes" Okamoto is making with his hands and the direction-shape of the arms, although they themselves are not the source of power (nor are the shoulders or upper back).
Aiki-age and Aiki-Sage
Here's another clip ("Daito-ryu Roppokai"), from a seminar in Hawaii in 1992. It includes some interesting concepts including the mechanism for directing aiki to the opponent's center of mass, and kata aiki.