The Rhomboids are so important when it comes to opening the chest. Contraction of these muscles draws the scapula (shoulder blades) towards the mid-line in order to express the heart. I always remind my yogis to pin their shoulder blades behind the heart and express the heart center. Postures such as Garudasana helps to stretch these muscles. It is so important to counteract the contraction aspect that as yoga teachers we always talk about.Other poses where the rhomboids play an important part are Verabhadrasana 2, Trikonasana and Marichanyasana 1. All of these poses call for contraction of the rhomboids.