When channeling Reiki, the heat we experience while the energy is being pulled through us by the receiver, indicates a blockage (or resistance to energy flow) in the area of the body of the receiver we are working on. The heat usually dissolves the blockage so that the energy can flow again, according to one Reiki Master Teacher and author.
The constriction or blocked/dense area of energy is vibrating at a lower frequency which indicated that the emotions of fear, worry, anger, grief, or depression have become stuck in this area. When you bring your Reiki hands to the area, Reiki raises the vibrational frequency of the area and dissovles the blockage.
I had read previously that Reiki is a very high vibration or frequency of energy. When we are channeling it we are aligning the receiver to this frequency which brings about the healing. As that high frequency or vibration of energy is running through our entire physical and energetic body while we are channeling it, then we also receive a healing or alignment. What an incredible gift Reiki is to the world. Imagine if every household had a Reiki practitioner in it all over the planet. Maybe there would finally be Peace on Earth.