Ultrasound uses high frequency sound waves (not within the range we can hear) to stimulate the deep tissues within the body. By passing an ultrasound probe over your body, deep tissues are stimulated by the vibration of the sound wave. This leads to warming and increased blood flow to these tissues.
Electrical stimulation is a therapy that passes an electrical current to an affected area. Nerve conduction within the region is altered, which can in turn alter muscle contractility. Blood flow to these tissues is also increased with electrical stimulation. Patients often experience diminished pain after this electrical stimulation of treatment.