Influenced by Bernard, D'Arsonval decided to devote his life to research. In 1892, he became director of the new laboratory of biophysics at the College de France and continued in that post until 1910. His main contributions were in electrophysiology. From 1889 D'Arsonval did the first research on the physiological effects of alternating current on the body. He discovered that currents with frequency over 5,000 Hz did not cause the muscular contractions and nerve stimulation effects of electric shock. Instead they seemed to have beneficial effects. He pioneered the therapeutic application of high frequency current to the body, founding the field of electrotherapy. He developed a spark-excited resonant circuit to generate currents of 0.5-2 MHz called "D'Arsonval currents" for therapy, which became known as "D'Arsonvalization". It was later used for diathermy.
