Which depth corresponds to deep heating?

• A. 1-3 cm
• B. 5-7 cm
• C. 3-5 cm
• D. 7-9 cm

Answer: (C)

Deep heating is about warming tissues that lie several centimeters below the skin, targeting muscles and deeper connective tissues rather than just the skin and fat. About 3 to 5 cm below the surface is the typical depth range for deep heating modalities, which is why this option is the best choice. It aligns with how energy from methods like diathermy or focused ultrasound is intended to penetrate to mid-depth structures.

The shallower depth (1–3 cm) is mainly superficial heating, affecting the skin and subcutaneous tissue. Going deeper than 5 cm—such as 5–7 cm or 7–9 cm—moves into depths that are harder to achieve reliably with standard deep-heating therapies and risks uneven heating or insufficient energy delivery to the target tissues.