Techniques which utilize deep tissue/deep muscle are administered to affect the sub-layer of musculature and fascia.  These techniques require more advanced training and more thorough understanding of anatomy and physiology.  The muscles must be relaxed in order to effective perform deep tissue massage, otherwise tight surface muscles prevent the practitioner from reaching deeper musculature.  It helps with chronic muscular pain and injury rehabilitation, and reduces inflammation-related pain caused by arthritis and tendonitis.  It is generally integrated with other massage techniques.