The lymphatic system, which is closely linked with the immune system, helps our body by moving and excreting waste products, cell debris, toxicities and other foreign material. Our cells function by releasing these waste products and then replenishes by absorbing nutrients from the surrounding extracellular fluid. When the skin is pulled up it removes stagnant blood and toxicicities to the surface. The new created space formed by the suction than allows new blood to fill this space which brings fresh nutrient filled blood which aids in supporting the body's own healing properties.
ScienceDaily (June 25, 2009) — A German study published in The Journal of Pain showed that an external suction technique mainly used outside the U.S., called cupping, is effective for providing temporary relief of pain from carpal tunnel syndrome (CPS).
In Traditional Chinese Medicine, tight and painful back is caused by invading "pathogenic factors" of cold, damp, heat, or wind, which in turn cause "Qi" stagnation or blood stasis. Cupping and gua sha were said to release the stagnation and bring pathogenic factors and toxins to the skin surface where they could be released, and in turn to restore the natural flow of Qi and Blood.
Gua Sha is creating controlled damage of fragile tissue. Muscles and sinews that are chronically over-tight due to injury or compensating for some other problem develop poor circulation and have increased metabolic needs. The result is, malnourished and degenerate tissue that is not able to adequately receive needed nutrients or clear waste and debri. By breaking some of the tissue in a controlled way, gua sha serves to signal a red flag for the body to replace the tissue quickly and to restore blood supply and function. Before this, the tissues are just holding and getting by. When cells are ruptured open, they send strong inflammatory signals to the body to increase blood supply and to permit the entry of healing fluids and immune cells to clean and repair the site of injury.