Types of Electrical Therapy Alternating Current
Electrical stimulation in physical therapy is becoming a widely-used method for pain management and rehabilitation. It can help alleviate or eliminate discomfort, improve motor function, and enhance quality of life. Furthermore, electrical stimulation may reduce inflammation and promote healing.
Electrical therapy with alternating current is available, including TENS (transcutaneous electrical nerve stimulation), IFC (infrared frequency current), BMAC (burst modulated AC) and ACS (alternating current sinusoidal or square pulses). Each method has its advantages and drawbacks and should be chosen based on the individual needs of the patient.
Stimulation with alternating current is a safe and well-tolerated form of electrotherapy. Its principles are grounded in physics and mathematics, as demonstrated by Ohm’s law: intensity depends on voltage and tissue resistance. Amplitude and frequency also play an important role; the magnitude of the stimulus determines whether it causes sensory reaction or motor response.
Burst-modulated alternating current (BMAC) is the most prevalent type of kilohertz-frequency AC and typically delivered in short bursts. Compared to PC, continuous AC, Russian current or interferential current stimulation, this form of electrotherapy offers more comfort and effectiveness.
Low-frequency PC produces more MEIT than higher frequencies but does not cause the same level of discomfort. This is because the skin’s impedance is lower at high AC frequencies, meaning less electrical energy is dissipated.
Alternating current has been found to be a safer and more tolerable treatment option than continuous or Russian currents, since its DC component is always zero, protecting skin under the electrode from chemical damage.
Physiologically, alternating current is more beneficial for patients with chronic muscle weakness and spasticity than other forms of electrical stimulation, such as high-frequency alternating current (HFAC). Furthermore, its application range is wider than other modalities.
Neuromodulation with alternating current can be used to block nerve signals, creating a localized inhibition of the peripheral nervous system. The minimum amplitude required to achieve this effect is called the block threshold and may vary depending on the waveform, frequency and electrode position. It has unique nerve blocking properties which are quickly reversible when the stimulus is turned off.
Electromyography is a non-invasive test to measure the muscle’s capacity to generate tetanic contractions at specific frequencies. To do this, an electrode is placed over the muscle and short (less than 1 ms) pulses applied over it; if a response occurs, then that muscle has intact peripheral innervation.
Other tests to measure muscle contraction capacity are employed to confirm if the muscle is functioning optimally. Many of these can be conducted with the same electrode and yield similar results.
Reflex diagnostic testing is an electrophysiological test that can be conducted with a single electrode over the motor point area. The electrode is stimulated with short (less than one ms) pulses at a frequency that should elicit a tetanic or sustained contraction in the muscle; if no such response occurs, damage has likely already taken place.