One of the most common types of physical therapy equipment is therapeutic modalities. These include machines that utilize heat, cold, ultrasound, and electrical stimulation to alleviate pain, reduce inflammation, and promote healing. For instance, ultrasound machines emit sound waves that stimulate tissues, enhancing blood flow and promoting cellular repair. TENS (Transcutaneous Electrical Nerve Stimulation) units are also prevalent; they provide electrical impulses to relieve pain by disrupting the pain signals sent to the brain.