In Move Within Yoga, all our poses are 'resting' to some extent. By adopting poses for a period of time, blockages in our physical body are released. By observing the free flow of breath and actively guiding our body into further openness, we also release congestion in our prana, or etheric body - the invisible sheath around our physical being that belongs to nature and is interwoven with our thoughts. Prana literally means life-energy.
Downward triangle looks like a triangle and, just like any other triangle pose, is a representation of the three planes of human existence: our body, our soul and spirit. On a more physical level, all triangle poses consist of the Big Three: light head and neck, stable legs and hips, and an active dynamic middle or solar plexus chakra. The mid-area corresponds to the apex of our triangle. The more we guide the middle, the more perception we develop about this chakra. The more we can gather attention to the solar plexus, the more force is concentrated here and the more dynamic the pose becomes.
To get more of an expansion out of this rather closed-in-on-itself pose, slowly lift one leg up until it meets natural resistance. Don't push the leg up higher than it's naturally able to move. Instead, continue to build focus in the solar plex, straighten the standing leg and then test the raised leg. I say test because it's a checking in with the raised leg: has the body softened and opened to allow a further gradual guiding up? Usually, the student finds it can indeed raise the leg a little higher without force or strain. Return back to the solar plexus and again test the leg. No matter how high you manage to raise the leg, observe the expansionary quality of the solar plexus and the triangle pose.