One of the benefits of regular Taiji practice is the release of stress and unwanted postural tension, allowing the breath to flow smoothly and unhindered.
Martially, this aids in the efficient transmission of force, without interference of postural muscle tension upon functional muscle use; it also allows the practitioner to move in a relaxed way and conserve stamina.
In the video below Dave discusses the concepts of tension, relaxation and breathing as they relate to the Taiji hand form postures and movements.