Summary
Highlights
High-frequency currents are defined as those exceeding 5,000 to 10,000 Hz, depending on the bibliography. Unlike low and medium frequencies that stimulate nerves, high-frequency currents primarily produce thermal effects by transforming electrical energy into heat, accelerating metabolic responses. This energy is electromagnetic, which converts to infrared, leading to a warming effect.
High-frequency currents range from 0.5 MHz to 2450 MHz, including D'Arsonval currents, diathermy, and various types of shortwave, ultrashortwave, and microwaves. This video focuses on shortwave therapy, which is characterized by its ability to penetrate both conductive and non-conductive materials through different mechanisms.
Shortwave therapy utilizes a conduction mechanism in conductive materials. This involves free ions dissolved in a substance, which oscillate rapidly between two electrodes due to the alternating current. This oscillation generates kinetic energy that transforms into thermal energy. The heating effect is greater in tissues with lower electrical resistance and a rich ion or polarized molecule content.
The displacement mechanism occurs in dielectric tissues which are not rich in water or ions. Here, fixed charges (bipolar molecules) reorient themselves according to the fluctuating polarity of the electrodes. The friction caused by these reorienting molecules, packed closely together without mobility, generates heat. The greater the dielectric constant of the tissue, the more significant the heating by this mechanism.
The heat generated by shortwave therapy is explained by Joule's Law, which states that the quantity of thermal energy produced is proportional to the square of the intensity, resistance, time, and a constant. In shortwave therapy, power (intensity squared multiplied by resistance) and time are the primary variables considered for practical application.