What is the primary function of a heat pack in therapy?

The primary function of a heat pack in therapy is to relax muscles and improve circulation. When heat is applied to an area of the body, it causes the blood vessels to dilate, increasing blood flow. This enhanced circulation can help deliver more oxygen and nutrients to the tissues while also aiding in the removal of metabolic waste. The heat relaxes muscle fibers, which can reduce muscle tension, alleviate stiffness, and improve overall comfort. Consequently, heat therapy is often used for conditions like chronic pain, muscle spasms, and stress.

Taking into consideration the other options, while increasing muscle strength, providing pain relief through cold, and enhancing flexibility in joints are important aspects of physical therapy, they do not adequately represent the primary purpose of applying heat as a therapeutic measure. Each of those approaches utilizes different modalities or techniques suited for specific therapeutic goals, whereas heat specifically targets relaxation and circulation.