Ardha Navasana (Half Boat Pose) registers as 2* on Iyengar’s 60* scale of difficulty and is a relative of Paripurna Navasana.
Iyengar says, “In the beginning, the back is too weak to bear the strain of the pose.” Many practitioners, myself included, can empathize with this statement. When I try to bring my legs 30 to 35 degrees from the floor as Iyengar instructs, I have a tendency to arch my lower back as a way of reducing strain on this area of my spine. But, this misalignment minimizes the benefits of the pose.
Rather than focusing on drawing your legs closer to the floor, focus on maintaining a flat, strong lower back. As soon as you sense your lumbar spine curving, stop lowering your legs to the floor. You’ve reached your limit within the pose for now.
Once you avoid straining your lower back, the opportunity to develop strength within the asana unfolds. Both Paripurna Navasana and Ardha Navasana can strengthen the muscles of the back as well as internal organs (the intestines in Paripurna Navasana; the liver, the gal bladder and the spleen in Ardha Navasana). As Iyengar says, “The importance of having a healthy lower back can be realised if we watch old people when they sit down, get up and walk, for consciously or unconsciously they support their backs with their hands. This indicates that the back is weak and cannot withstand the strain. As long as it is strong and needs no support, one feels young though advanced in age. [Paripurna Navasana and Ardha Navasana] bring life and vigour to the back and enable us to grow old gracefully and comfortably.”
Move from strain to strength in your personal practice of Ardha Navasana by listening to your lumbar spine and approaching the asana gradually.