The masseter is the strongest muscle in the human body and is responsible for elevating the lower jaw (mandible) and enabling us to eat and speak. Jaw issues such as temporomandibular joint (TMJ) disorder can cause pain and discomfort in the jaw joint and muscles, and can even lead to lockjaw. This can be caused by teeth grinding or jaw clenching habits. To avoid and treat this, there are exercises and relaxation techniques that can be done at home or with a physical therapist to strengthen and relax the jaw muscles. tmj disorder body balancing jaw pain