Although the concept of prana vayu might be quite a subtle and philosophical one at first sight, I find that it can be demonstrated very clearly through the opposition of forces applicable in asana. A grounding and at the same time rebounding movement is obvious in many standing postures and can be emphasized even more by a subtle movement with the breath. Virabadhrasana I is a good example, where we ground down through the legs, strongly connecting to the floor through the feet and at the same time reach up to the sky through the fingertips. Bending the front knee just slightly further on each exhalation will access apana – the grounding force – and lifting the hips and straigthening the front leg ever so slightly on each inhalation will demonstrate the upward lifting movements of prana and udana.
Equally samana and vyana vayu can be emphasized by moving through a “tiger stretch”, from hands and knees on the floor straightening one leg back and up, radiating out from the core (vyana vayu) and exhaling the leg into the chest, contracting from the core as the back rounds and the head touches the knee (samana vayu).
Flowing through asanas with an awareness of the movements of prana can promote a greater sense of opening or releasing of areas that feel held or tense and enhance the breath flow in an asana. It can also help to demonstrate the effects of bandhas through the interaction of grounding and rising forces, promote a sense of space in the joints and a sense of balance.