In honor of your last post, I taught a fingertip awareness oriented class this morning. I have found that asking my students to energize through their fingertips never inspires much visible action. But asking them to extend their arms as though they begin all the way at their hips is rather effective. Also, when having them walk their hands out from Uttanasana to Down Dog, I borrowed your image of the fingertips as antennae, probing and exploring their way to the top of the mat. Just as you advocated, it kept their shoulder-blades on their backs and their heart-center's open - it was a lovely thing to behold.
Doing all of the fingertip work led to the arms. I am constantly amazed by how much work there is to find in your arms if you TRULY straighten them and hug the muscles onto the bones. Standing in Utthita Hastasana, turning the palms to face away from you, and then pressing down through the air as though you were moving through molasses, or pressing down on 50 pound weights will give you a solid workout. Do it 3 times and you may break a sweat. Good times.
Speaking of truly straight joints, one of my teachers was recently talking about the importance of fully straightening our elbows and knees and in particular, HOW to open the backs of the knees. She then got onto the topic of Light Therapy and how it's being used on the backs of joints to minimize and treat depression. It was the first I had heard of it, but Google provided me with an abundance of evidence that shining bright lights can reduce chronic pain, heal diabetic ulcers, and even re-set the body's circadian rhythms! No idea if any of it is true but I figure I'll keep my joints straight as can be while the medical professionals sort this one out.
Light: making the world go round, protecting the integrity of our joints, and now, curing the blues!