A modality is a type of electrical, thermal, or mechanical energy that stimulates a physiological change in the body. Physical modalities are physical agents that produce a specific therapeutic response in biological tissue. Ultrasound, electronic muscle stimulation (EMS), and heat/cold are examples of physical modalities used to treat patients after an accident or during post surgical rehabilitation. These effective and gentle modalities reduce pain, improve circulation, increased tissue regeneration, and decrease swelling after an injury.