Which modality requires four leads and tends to penetrate deeper into tissue?

• A. Ultrasound
• B. Heat Pack
• C. IFC
• D. TENS

Answer: (C)

Interferential current therapy uses two separate current sources delivered through four electrodes. When these currents intersect inside the tissues, they create a beat frequency that modulates the tissue at depth. This interference pattern allows current to reach deeper structures while reducing skin impedance, so the stimulation is felt more deeply than with many other modalities.

Ultrasound works with acoustic energy and doesn’t rely on crossing electrical paths; a heat pack provides thermal energy without any electrical leads; and TENS typically uses two leads to stimulate superficial nerves. The four-lead setup and the deep-reaching interference make interferential current therapy the modality that tends to penetrate deeper into tissue.