The triangle pose is the series’ lateral stretch for the spine. In it, we extend and strengthen the muscles of the back and the spine itself in a lateral-left and lateral-right direction. As with all the stretches of the spine, energy is released along the spinal column, creating heat and energy in the body.
Swami Vishnudevananda described this asana as follows:
Triangle pose tones the spinal nerves and the abdominal organs, increases peristalsis of the bowels and invigorates the appetite. The body becomes light. The trunk muscles are contracted, relaxed and stretched. The spine is bent laterally on both sides and the muscles are fully stretched. This keeps the spine elastic.