Hey Docs! For the last couple of weeks I have been getting a burning sensation while stretching on the back of my left heel. It only happens when I do such stretches as the down dog where my hamstrings are also being stretched. I can do simple calf stretches without any pain. I had this once before on my right heel and it went away eventually. It never hurts while doing any other excercise and it gets better the more I stretch out. Any idea what this is and how to help it go away? It's not a big deal, but it makes going to my yoga class quite painful.