Which of the following is NOT listed as a superficial heat modality in the material?

• A. Hydrocollator packs
• B. Paraffin
• C. Ultrasound
• D. Infrared light

Answer: (C)

The key idea is that superficial heat modalities deliver heat mainly to tissues right under the skin, through conduction from a hot surface or through radiant heat. Hydrocollator packs and paraffin wax rely on conduction to warm the superficial layers, and infrared light provides radiant heat that primarily warms surface tissues as well. Ultrasound, on the other hand, uses acoustic energy that penetrates deeper into tissues and is absorbed to produce heating within muscles and connective tissue beneath the surface. Because its heating effect can reach several centimeters beneath the skin, ultrasound is regarded as a deep heating modality rather than a superficial one.