What is burst-modulated (Russian) current and its purported benefit?

• A. A low-frequency continuous current for endurance
• B. A high-frequency carrier around 2500 Hz delivered in bursts with a lower-frequency envelope; aims to improve comfort and deeper penetration while producing tetanic contractions
• C. A direct current for muscle conditioning
• D. A random pulsed current for pain modulation

Answer: (B)

Burst-modulated (Russian) current uses a high-frequency carrier, typically around 2,500 Hz, that is delivered in short bursts. These bursts are grouped and separated by brief off times, creating a lower-frequency envelope—around 50 Hz—that the muscle actually responds to. The high-frequency carrier reduces cutaneous sensation and skin impedance, allowing a higher total current with more comfortable application and deeper penetration into the tissue. The envelope at a tetanus-range frequency produces a smooth, strong contraction rather than separate twitches. So the combination aims to give deep, strong, tetanic contractions with greater comfort, which is why this option best describes burst-modulated current.